RIP Z80 - Page 1
Forum section: electronics / general

author: tchicago
author_rank: Regular Contributor
timestamp: April 20, 2024, 05:31:11 am
content: Zilog announced end of life of Z80, but it is still being manufactured as of now!https://www.mouser.com/PCN/Littelfuse_PCN_Z84C00.pdf--- "Last time buy orders will be accepted until June 14th, 2024."Maybe I should order a couple of them with a cool last production date code of 2024 as the memorabilia items.Zilog brand apparently belongs to Littelfuse these days.

author: brucehoult
author_rank: Super Contributor
timestamp: April 20, 2024, 05:43:15 am
content: The votes are in. 6502 outlasts Z80 .Z80 cores will still be in other chips -- it's just the DIP40 (etc?) bare CPU that is going away. To be fair that's 65C02, the NMOS chip went away a long time ago. And there will still be eZ80.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 20, 2024, 06:09:23 am
content: Incredible lifetime!

author: lunix
author_rank: Contributor
timestamp: April 20, 2024, 06:25:53 am
content: My very first commercial embedded project used a Z80. Then I fell in love with the 6809. Then the PIC. A couple of decades after that first one, Zilog was pushing a Z80-based microcontroller, and had a giveaway for a design contest. I got a kit. Then I wrote to them that it had a dead short across the power supply, and they sent a replacement. That one didn't work either. And that was my last Zilog experience. I'm still sad about that. It was a better 8080, and those days are long in the past now.

author: woofy
author_rank: Frequent Contributor
timestamp: April 20, 2024, 06:56:34 pm
content: Zilog could at least wait until March 2026, just to give the Z80 a 50 year lifetime.Federico Faggin first came up with the idea for the Z80 in 1974, so I suppose it just about has its 50 years, though the first actual Z80's were born in 1976.I cut my teeth on the Z80 and have since purchased many thousands for control products.R.I.P Z80.

author: coppice
author_rank: Super Contributor
timestamp: April 20, 2024, 07:02:37 pm
content: Quote from: brucehoult on April 20, 2024, 05:43:15 amSurely the Z80 still being made has as little in common with the original silicon as the current 65C02.I played with a chip some years ago with a 1GHz Z80 core in it. I can't remember what the actual chip was, but cranking a Z80 up to 1GHz seemed amusing enough for me to have a short tinker with it.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 20, 2024, 07:14:42 pm
content: My first Z80 design was a home computer, compatible with both ZX Spectrum and CP/M. That was happening sometime during the late 80's.https://hackaday.io/project/1411-xor-hobby-a-vintage-z80-computer-prototype

author: tchicago
author_rank: Regular Contributor
timestamp: April 20, 2024, 08:56:05 pm
content: Quote from: RoGeorge on April 20, 2024, 07:14:42 pmOh no, you breadboarded it! Must have been an immense amount of work.My Spectrum was the second homebuilt computer - using a common Lviv variant PCB. It looked just like this onehttps://speccy.info/%D0%A4%D0%B0%D0%B9%D0%BB:Lvov1.jpgBut in general, the Spectrum was just for games, and not serious learning of computer science. For the latter, I kept using my first homebuilt computer based on i8080 (https://en.wikipedia.org/wiki/Radio-86RK). It had those big serious interface chips like i8257, i8275, and i8255 which were fun to learn and program.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 20, 2024, 09:58:22 pm
content: Some games for the ZX Spectrum were incredibly good for an 8-bit 3.5MHz Z80 that was also bit-banging the sound, reading the keyboard, refreshing the DRAM, and updating the image for each frame, all at the same time. I remember Knight Lore was a total shock back then. It was looking amazingly good:The next jaw-dropping game for me was to be many years later, around the year 2000 when Half-Life came out (for PC).By that time Z80 was rather rare, the IBM-PC standard was everywhere, and Z80 was only used for automations and such. Z80 has had so far an outstandingly long life, considering with how many microcontrollers it was competing over the last 30 years or so.

author: woofy
author_rank: Frequent Contributor
timestamp: April 20, 2024, 10:48:24 pm
content: DRAM refresh was built in, with a 7-bit counter output during the M1 cycles of an instruction read, but yeah, it was quite amazing what programmers could do with a few MHz in and 8-bit processor.

author: MathWizard
author_rank: Super Contributor
timestamp: April 21, 2024, 04:59:03 am
content: Was/Is the Z80 copied a lot, by counterfeiter's? I wonder where all the ebay ones come from.

author: nctnico
author_rank: Super Contributor
timestamp: April 21, 2024, 06:07:51 am
content: That is a long lifetime indeed. There was a time where I knew most of the Z80's instruction set by opcode. Goodbeye old friend...

author: Howardlong
author_rank: Super Contributor
timestamp: April 21, 2024, 08:46:55 am
content: Quote from: woofy on April 20, 2024, 10:48:24 pmYes, DRAM refresh was "built in" in that there was a counter and notification that it's safe to do a row refresh.Not so great was that to get the timings into spec that the DRAM of the day required, a fair bit of fettling and empirical work with glue logic & RC networks was required to get the RAS/CAS and setup/hold timings to work within tolerances, particularly if you were doing a production run.It became easier and cheaper to stick in static RAM as time proceeded, what with higher densities, substantially reduced glue logic, and dropping prices.

author: woofy
author_rank: Frequent Contributor
timestamp: April 21, 2024, 09:39:32 am
content: Quote from: Howardlong on April 21, 2024, 08:46:55 amYeah, my first Z80 design used 8 x 4164 dram's. It never sold many, nobody ever needed that much ram on a controller in those days and subsequent revisions used 6116 and 6164 sram's.That was my only time putting dram's on the Z80.

author: iMo
author_rank: Super Contributor
timestamp: April 21, 2024, 09:55:53 am
content: I got my first Z80 inside the ZX81 kit when it appeared, added a DIY 16kB module made of 8x4116. Then ZX Spectrum. Messed for while with U880D. Then switched to 68k and never went back to the Z80. It was a nice time, indeed..

author: coppice
author_rank: Super Contributor
timestamp: April 21, 2024, 12:07:56 pm
content: Quote from: Howardlong on April 21, 2024, 08:46:55 amControlling DRAM took quite a few chips in those days, yet the total logic involved was not that great. Zilog threw the refresh counter into the MPU, but left the rest out. I was always puzzled that nobody tried throwing the whole DRAM control thing into their MPU. Its not like getting the feature set right was a problem. From the earliest days practically all DRAMs were drop in replacements for each other, with a well defined path to the needs of future generations.

author: brucehoult
author_rank: Super Contributor
timestamp: April 21, 2024, 10:08:37 pm
content: A couple of friend and I designed and built a wire-wrapped 6809 machine in 1983. We thought about 68000 but it was expensive and the 6809's 8x8->16 multiply was faster than the 68k's (wider) multiply, and the 8x8 suited the music synthesis one of us wanted to do.We did DRAM refresh in software, with an interrupt causing a page of NOPs to be executed. Or that could be turned off when you knew the software would be doing sufficient memory references itself -- or just masked for a short while for a critical loop.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: April 21, 2024, 10:26:10 pm
content: Quote from: MathWizard on April 21, 2024, 04:59:03 amIn period there were several clones by Warsaw Pact states - East Germany, Soviet Union, Romania.It's doubtful that's what ebay counterfeiters are selling today. I believe they mostly are selling chips that aren't Z80s at all, or remarking older chips to appear newer.

author: coppice
author_rank: Super Contributor
timestamp: April 22, 2024, 04:11:59 pm
content: Quote from: brucehoult on April 21, 2024, 10:08:37 pmA lot of machines performed DRAM refresh in software. I've also seen a DMA channel committed to refresh. You still have to do things like RAS/CAS muxing in hardware. The refresh counting is only a modest part of the DRAM support problem.

author: SeanB
author_rank: Super Contributor
timestamp: April 22, 2024, 05:56:27 pm
content: The Zilog one might be stopping, but the Toshiba and Sharp units are likely to stay in production for a good number of years still, as they also have all the peripherals of the Z80 family inside the package, and thus you can make a complete SOC with them, as they all now have 32k of RAM and 32k of flash built in, though there are still a fair number made with older OTP Eprom memory, which is in a lot of industrial equipment, copiers and such, along with lots of other applications where they have a very long code base life, and are familiar with the design.

author: GromBeestje
author_rank: Frequent Contributor
timestamp: April 22, 2024, 06:11:24 pm
content: They have the peripherals inside the package? Something like the Zilog's eZ80? That one stays in production. It's the classic chips that go out of production. I was wondering if there was any of the other manufacturers still make the classic chips?

author: amyk
author_rank: Super Contributor
timestamp: April 23, 2024, 01:48:41 am
content: I think almost everyone has used a device with a Z80 core at some point in their lives, even after the 8-bit minicomputers faded away. Thehttps://en.wikipedia.org/wiki/S1_MP3_playerand the Texas Instruments calculators are the most prominent examples I can think of. (GameBoy doesn't count, as it's not truly compatible.)

author: wek
author_rank: Frequent Contributor
timestamp: April 23, 2024, 03:13:33 pm
content: Quote from: brucehoult on April 20, 2024, 05:43:15 amThere are still plenty of 8051 made, most of them binary-, some pin-, and maybe still a few of them clock- compatible with the original (1980).JW

author: peter-h
author_rank: Super Contributor
timestamp: April 23, 2024, 03:20:49 pm
content: I started on the Z80 too. A great chip and really versatile in its time.Today, most embedded stuff (except low end) is done in C and if the clock is fast enough the CPU architecture becomes almost irrelevant. And those who cut their teeth on the Z80 are mostly retired now.And few of the original products will be selling today; I still nominally sell a Z180 based box designed in 1991 but the volume is very low. There are still GA avionics (like the JPI EDM700 family) which use the original Z80, EPROM, SRAM but their sales will be very low too, even in that extremely slowly innovating field.How long a product can run is always a fun debate but the truly original DIP40 Z80 must have virtually ended. Even in the military sphere, things have moved on. The other day I saw the internals of the Javelin missile; a 30 year old design but still current on the Ukraine battlefield, which uses all kinds of expensive chips.Littelfuse owning Zilog is the ultimate insult; a shit company making boring stuff owning a one-time real innovator.

author: coppice
author_rank: Super Contributor
timestamp: April 23, 2024, 03:34:40 pm
content: Quote from: peter-h on April 23, 2024, 03:20:49 pmIf you try to sell an MCU to many large customers now they show no interest unless it has an ARM core, or perhaps increasingly a RiSC/V core. You can talk about a totally unsuitable chip for their needs, and they'll listen if is has an ARM core. You can talk about a great fit for their needs, and they are not listening simply because it doesn't have an ARM core. But the core is almost irrelevant, because almost all new MCU code is developed in C. The MCU's value is all about its unique qualities - interesting peripherals, special memory qualities, like error detection/correction or non-volatility, partitioning to meet regulatory requirements, etc.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: April 23, 2024, 08:34:13 pm
content: Quote from: SeanB on April 22, 2024, 05:56:27 pmYup, theprocess FABthat makes Zilog's CMOS version of the NMOS Z80, is being terminated. The NMOS Z80 is long gone.Zilog still have other CMOS process Z80 variants, as do other companies.Just like intel no longer publicly sells stand alone 8051, there are many companies making new-process 80C51 variants.The original 8051 has 8 bit opcode fetch, and 12 clocks per opcode.The newest 80C51's can fetch 24 bits of opcode in a single clock cycle, and run at 45Mhz +The 80C51 is the most widely sourced 8 bit MCU on the planet.

author: bson
author_rank: Unknown
timestamp: April 23, 2024, 09:17:12 pm
content: Quote from: coppice on April 21, 2024, 12:07:56 pmI built a numeric door lock in 1985 that could have different codes for different people and allowed tracking and revoking individual access. It had battery-backed SRAM so I used the refresh cycle to scan the keypad and pull the INT# pin if any key was pressed. I forget exactly what logic was used, but I thought it was pretty cool to get a hardware keypad scan with only one incremental logic IC. (A latch register of some variety.)

author: nimish
author_rank: Regular Contributor
timestamp: April 24, 2024, 01:01:53 am
content: Quote from: coppice on April 23, 2024, 03:34:40 pmARM cores have a far better software development toolkit than one-off proprietary architectures and you aren't forced to buy from a single vendor. Since software development is the most expensive part it pays to reduce those costs. Would you rather use LLVM 18 or some jank vendor gcc? Even RISC-V is kind of stuck here, CLIC isn't ratified yet either.So I'm not surprised they stop listening when someone proposes the use of a wacky new ISA for no really good reason.

author: brucehoult
author_rank: Super Contributor
timestamp: April 24, 2024, 01:21:56 am
content: Quote from: nimish on April 24, 2024, 01:01:53 amNot ratified, true, but frozen and very unlikely to change. It's currently in ARC (Architecture Review Committee) review, after which it needs Committee Chair and CTO sign-off, then a public review period, then the ratification vote. My guess is ratification will be around July.

author: peter-h
author_rank: Super Contributor
timestamp: April 24, 2024, 07:21:02 am
content: QuoteThat however is a reasonable approach.Nowadays, with a 168MHz core, 99% of applications can be done with 1 or 2 chips e.g. the 32F4xx. These have been around > 10 years, even the chinese do copies, the dev kits are free and well understood by anyone using them, the chips are $5 in quantity, and they are 10x to 100x fast enough for most jobs. I've just done a project with a 32F417 and I am certain I will not need to look at another CPU in the rest of my actuarial life expectancy (20 years). With ETH and USB done and working (not optimally but well enough) and with 21MHz SPI, I can do absolutely anything I have done since 1980 and absolutely anything I can imagine having to do. For highly specialised stuff e.g. a modern DSLR one needs specialised chips, but for nearly all "industrial control" and consumer stuff, more is not needed.The most important thing is preserving in-house dev expertise, because devs tend to care little for "your" company, and love picking the latest fancy parts (good for the CV, too) so you have to steer them to using the right parts. You can always tell when some company doesn't do this correctly; you get crap like 10.1k resistors all over the placeI can show you some Honeywell autopilot schematics...The Z80 performed this job for many years. There was simply no point in using the other "8/16" bit CPUs, for embedded work. And it had the massive advantage of a short learning curve. The RM was maybe 200 pages. All the product schematics ended up pretty much the same basic stuff. Today you have a 300 page DS, 2000 page RM, ~5000 pages ARM32 CPU RM... building up expertise with a popular chip has never been more important.What buggered the Z80 and Zilog, before the right time, was the 64k addressing. IAR C got around it reasonably well with their Large Model but linear addressing have the 68k a good start. Had the Z80 had even 20 bit addressing, a lot of other chips would have never got off the ground.

author: coppice
author_rank: Super Contributor
timestamp: April 24, 2024, 01:29:02 pm
content: Quote from: peter-h on April 24, 2024, 07:21:02 amYou must have worked on a very narrow range of MCU applications, or perhaps only on small volume products, to have such a view. The vast majority of MCUs produced are quite narrowly tailored to a few applications they suit well. If you don't think the chip is narrowly tailored you probably just don't recognise the applications it was tailored for, You gave no explanation for why an ARM core would be beneficial. Sticking with one maker, and their peripheral set, can be a big speed up in development work. Who cares what the core is, apart from a few special qualities like getting in and out of low power states, where a few designs excel?

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 24, 2024, 10:20:01 pm
content: Except if you are writing some generic RTOS, the core itself rarely matters as long as its meets the performance requirements you have. So, that's from the software POV.The point, as some have said already, is more with the toolchains. If it's an ARM core, you can use mainline GCC for ARM targets (or LLVM), you can (usually) use generic JTAG/SWD probes, and so on. More odd architectures will usually require very specific vendor tools, which you'll be tied to (and which may be expensive). Whether this is an issue in your particular case, only you can answer.

author: peter-h
author_rank: Super Contributor
timestamp: April 26, 2024, 04:27:20 pm
content: QuoteI think most MCUs are designed for a specific automotive or other consumer application, against a customer requirement for say 10M chips annually. This is pretty obvious with some chips like Siemens ones that go into ECUs but you rarely see them generally.But since almost nobody doing that is posting here (not allowed to, for a start) we are talking mostly about lower volume stuff.QuoteWe are saying the same thing, I think. A well managed company will make strategic choices in this area. They will also have direct accounts with firms like ST. They won't be searching Digikey for a suitable chip

author: coppice
author_rank: Super Contributor
timestamp: April 26, 2024, 04:41:32 pm
content: Quote from: peter-h on April 26, 2024, 04:27:20 pmThat used to be a common practice, but things have changed. Producing a new die is now so expensive vendors want to develop MCUs that can potentially cater to a whole application segment, rather than a particular customer. So they tend to survey customers, and try to figure out a feature set that will have broad enough appeal to capture a number of big players in that application space. Then they make the chip and offer it in their catalogue. This has created some interesting brinkmanship dynamics. Leave out one pin needed by some of the big players, and you can be out of the market. The few cents of extra hardware needed to simulate that missing pin can kill your chances. Throw in a few too many things, and pad out the pin count, and you might be too physically big or too expensive.Quote from: peter-h on April 26, 2024, 04:27:20 pmYou'd be surprised. A number of people here either work or used to work in high volume stuff.

author: brucehoult
author_rank: Super Contributor
timestamp: April 27, 2024, 12:32:33 am
content: Quote from: coppice on April 26, 2024, 04:41:32 pmI'm on the software side, not the chip/board side (though I do interact with those people from time to time), but ... would you consider Galaxy S / Galaxy Tab high volume? And the TVs. A lot of my work is in those. Well, and some upstreamed into generic Android too. And Firefox for that matter, but that was long ago.Back in, say, 2016, we prototyped a lot of stuff on Pi 3 and Odroid C2 (and the 32 bit but fast XU4 before that) before trying it on Google phones, and only finally on prototype Samsung ones. Now the latest things are being developed on VisionFive 2.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 27, 2024, 03:50:13 am
content: The high volume markets drive the chips (and the SW toolsets). The low volume folks have to dodge around and try to figure out where the high volume people are going so that their choices will meet their market needs. And there is a big split in the low volume market. Those who will be producing for years or even decades, and those who make a production run or two and then move on to the next model or product. That first group is the one that really needs to be clairvoyant or clever. Fortunately many of those old chip designs can be adequately emulated on current hardware allowing transparent to software and user replacements for ones that have gone EOL.

author: nimish
author_rank: Regular Contributor
timestamp: April 28, 2024, 05:13:39 am
content: Quote from: brucehoult on April 24, 2024, 01:21:56 amCool, I hope it'll work with the sifive/t-head/WCH implementations. I really would not want stuff likehttps://discourse.llvm.org/t/rfc-prestacked-annotation-to-solve-risc-v-interrupt-stacking-mess/74120proliferatingAnd a standardized debug adapter interface like ARM's SWD/DAP/coresight would be great too. Who the hell wants a different *-Link for every vendor?

author: brucehoult
author_rank: Super Contributor
timestamp: April 28, 2024, 07:00:12 am
content: Quote from: nimish on April 28, 2024, 05:13:39 amI don't have a problem with that proposal at all, or indeed even see the situation as a "mess".Some people are used to hardware saved registers on other ISAs and want that feature on their RISC-V processors, and probably more manufacturers than at present will (in my opinion) waste transistors that could have been used for better things (or just use less silicon) on duplicate register sets (worse) or a FSM to stack registers.Maybe the people who want to implement/use this will agree on a single spec for it, but as it's pretty much 100% "we think it give us a competitive advantage" thing I wouldn't hold my breath, at least in the short term.That's pretty much inevitable with a community-owned ISA. You can see it as a disadvantage, but I see it as a strength.And I think @jnk0le's proposal is both very easy to implement and solves the problem neatly. It makes perfect sense.

author: nimish
author_rank: Regular Contributor
timestamp: April 29, 2024, 11:14:13 pm
content: Quote from: brucehoult on April 28, 2024, 07:00:12 amDesign by committee is fine but I'd rather have had a finished baseline standard and then add the rest on as extensions. I don't care about this particular instance per se, but it is wild to not have an NVIC equivalent standardized.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 29, 2024, 11:34:34 pm
content: I don't see how "wild" it is. RISC-V was designed as a general-purpose, extensible ISA. Apart from the core functions, everything was left as future extensions. And that's part of its strength.Of course, it also leads to fragmentation, but that's unavoidable.If we nitpick, "x86" CPUs are also heavily fragmented, in that each new generation has added a large number of new instructions and features. So if you stick to the least common denominator, you're left with, not that much actually.The NVIC example is interesting and ill-positioned: indeed; the NVIC controller is only available on Cortex-M cores (so, in short, MCUs), while Cortex-A cores have a different interrupt controller. So there's also "fragmentation" even in the ARM world.Sure, those who are only interested in RISC-V MCUs for now may throw a tantrum, because it's fragmented even in this "niche". But that comes with openness and its relative youth. When CLIC is ratified, sure vendors are likely to adopt it, but still, some may add particular features to gain a competitive advantage, that may require specific, non-standard support. And that's good. I like having options.The fact that a given different implementation of an interrupt controller may impact compilers or not is another story. Not all implementations require anything more than the basic "interrupt" behavior of GCC/Clang. And here, once this register saving thing is settled (which will be generic enough to accomodate pretty much all cases), the rest will only require accessing some CSRs and memory-mapped registers, so there shouldn't be any more vendor-specific support required in compilers.

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: April 29, 2024, 11:39:26 pm
content: I wrote the software for a Teletext adaptor for the Sinclair Spectrum in around 83/84.It was fun trying to fit in 40 colour attributes into a 32 attribute screen.Worked out ok in the end.For its time the Z80 was an a great processor to write code for.If they had made a 32 bit Z80 we might all have pc's with Z80 in them.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 29, 2024, 11:44:12 pm
content: Quote from: nigelwright7557 on April 29, 2024, 11:39:26 pmThey made a 16-bit, and even 32-bit derivative of the Z80, actually. The Z280 and Z8000 (16-bit), and the Z80000 (32-bit). They didn't get a lot of traction. But that existed.

author: oPossum
author_rank: Super Contributor
timestamp: April 29, 2024, 11:48:24 pm
content: Steve Ciarcia (Byte/Circuit Cellar) made a Z8000 coprocessor for the PC.https://www.smbaker.com/the-trump-card-zilog-z8000-comprocessor-card-for-the-ibm-pchttp://www.dtweed.com/circuitcellar/trumpcrd.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: April 29, 2024, 11:57:23 pm
content: how many years until we can make a z80 DIY with low cost?a few more generations of UV exposure projectors....

author: peter-h
author_rank: Super Contributor
timestamp: April 30, 2024, 06:20:43 am
content: QuoteAccording to Zilog, I did the first design-in in the UK for the Z280 c. 1987 and second in Europe (someone in Germany did another one). A great printer/plotter sharing box called MultibufferSold really well; £2500 for the 4MB versionNothing on google; it is too old, I left the company in 1991 and they went bust in 1993 and then Windoze finally got printer sharing working...It was still a 16 bit CPU. The address range was 16MB but via a MMU. You could do the same thing with a Z80 and bank switching. But it had extra instructions and a cache which made it run much faster per MHz than a Z80. Very good for embedded. Nice features like a rapid cache fill using the typical EPROM fast read if /CS=0 and you increment the address; most EPROMs managed about 50ns. I wrote a simple RTOS for it; posted the source here somewhere.The Z8000 also had a 64k address space but with segmentation like the 8086/186/286. Yes you could have built a "PC" with it but by then Intel had a big lead.The Z80000 did exist but only NMOS and ran pretty hot. AIUI it got one design-in: some sort of laser printer.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 30, 2024, 06:56:43 am
content: There was some kind of PC with a Z8001 (discovered it a few months ago) from Olivetti:You can still play with the Z280 these days:https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:z280rc

author: peter-h
author_rank: Super Contributor
timestamp: April 30, 2024, 08:09:13 am
content: Yes; the Olivetti machine. Never sold AFAIK. Had a unix OS.I wonder where that firm gets the Z280 chips? Must be from some used stock source.

author: woofy
author_rank: Frequent Contributor
timestamp: April 30, 2024, 11:38:55 am
content: Zilog kind of lost focus when Federico Faggin stepped down in 1980. I remember all the hype around the Z800 and looking forward to the new chip, but it was endlessly delayed. Zilog was working on the Z80000 32 bit and Z8000 16 bit non-Z80 compatible processors. The Z800 finally appeared as the Z280 10 years after the Z80, way too late. They had some success with the Z180 which was a copy of Hitachi's 64180 and their Z8 embedded controller, but really, it was game over.

author: Howardlong
author_rank: Super Contributor
timestamp: April 30, 2024, 03:48:52 pm
content: I worked on a Z8000 based multiuser system with dumb terminals running Pick (anyone remember that?) around 1987 thru 1989, including offering Mac based terminal emulator for it so copy could be keyed into the dumb terminals, then imported into the Mac for desktop publishing.A friend of mine developed his own Eurocard based systems based around the Z8000 around this time, but as others have indicated, Intel was the way everything was going.

author: coppice
author_rank: Super Contributor
timestamp: April 30, 2024, 06:59:19 pm
content: Quote from: woofy on April 30, 2024, 11:38:55 amI think you must be talking about the Z8000. The Z800 was a later part. Zilog hit severe process problems with the Z8000 family, which was supposed to be launched with quite high performance, AMD had their second sourced parts ready for the whole family, and couldn't sell them as their agreement with Zilog said Zilog had to get to market first. This proved to be a dumb idea, as the whole bundle was so late to market everybody moved on, and the Z8000 was toast. AMD could have kept things alive until Zilog was able to ship.Did any Z80000 parts ever ship?

author: coppice
author_rank: Super Contributor
timestamp: April 30, 2024, 07:01:50 pm
content: Quote from: Howardlong on April 30, 2024, 03:48:52 pmAre you sure you have those dates right, or did you mean the Z80000? The Z8000 was pretty much dead before 1987. I wasn't sure if the Z80000 ever shipped, but if it did, it should have been around 1987.

author: woofy
author_rank: Frequent Contributor
timestamp: April 30, 2024, 10:07:31 pm
content: Yes, Z8000 was first, but was not Z80 compatible. The Z800 was Z80 compatible.. The Z280 was essentially an update the Z800 design.

author: brucehoult
author_rank: Super Contributor
timestamp: April 30, 2024, 10:27:54 pm
content: Quote from: Howardlong on April 30, 2024, 03:48:52 pmAn ex university classmate was using Pick at their city council work and showed me around it, but I think it was running on a Pr1me machine (which I wrote a small system in COBOL on in the 82/83 summer holidays at another council, but that was running regular PrimeOS).My Z8000 experience was a System 8000 Unix machine at university in 1984. It was the first real *nix I used and first exposure to vi. It was closer to a souped-up PDP-11 than to a VAX. I think we would have preferred a 32016 or 32032 machine but they weren't available yet, or too expensive or something. We had a project to support several programming languages (Modula 2 and some local student languages such as Lawrence D'Oliviero's "Peano" on several different ISAs (VAX, Z8k, M6809), and develop an intermediate representation, optimiser etc that could work with all combinations. Not an original idea but no one had made it work well at the time. Of course GCC and LLVM and others (Microsoft CIL) do today.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 30, 2024, 10:37:03 pm
content: Quote from: peter-h on April 30, 2024, 08:09:13 amNope. Market lifetime was about 2 years, and they sold about 50,000 in the first year, according to the Wikipedia article. Sales plummeted after that, so I don't know exactly how many they sold in total. Probably under 100k. That's not what they expected, but not ridiculous either.And the OS was not Unix at all - it was some kind of proprietary OS (single user, single task) which was part of the issue. Had they ported CP/M right from the start, the machine may have had a lot greater success. They did provide a CP/M emulator later on, but it was too late.https://en.wikipedia.org/wiki/Olivetti_M20its successor was just some PC "compatible" (M24).It's easy to claim to know, in restrospect, what they should or shouldn't have done, or that the IBM PC would become a de-facto standard, but it was absolutely not in the late seventies, when the M20 (and many other machines) was designed, and the IBM PC wasn't even a thing yet.Quote from: peter-h on April 30, 2024, 08:09:13 amNot sure. I couldn't find any myself through the usual channels.The Z180 is still available at Digikey though.

author: coppice
author_rank: Super Contributor
timestamp: May 01, 2024, 01:09:45 am
content: Quote from: brucehoult on April 30, 2024, 10:27:54 pmYou might have preferred at 32032, but only masochists preferred the 32016. It was very buggy. By the time they got the 32032 out and cleaned things up they were too far behind in performance the get anywhere. The 68020 had already got into most of the workstations.

author: coppice
author_rank: Super Contributor
timestamp: May 01, 2024, 01:17:57 am
content: Quote from: Howardlong on April 30, 2024, 03:48:52 pmThere was a time when Pick seemed to be everywhere for modest sized database needs. It seemed to be doing great, until the relational databases started to roll in.

author: peter-h
author_rank: Super Contributor
timestamp: May 01, 2024, 06:19:49 am
content: I still make a Z180 product, though not sold any for about a year.Remember the Z180 was sold in two versions: a "mask 160" or some such, and the latest one which has a broken UART hardware handshake. When the UART bug was found, Zilog did not have the resources to do another mask so they continued to sell the older one under that funny nameI never used the Hitachi 64180 in production, though I did start with a huge ceramic version with an EPROM window. Hitachi sold a lot of the 64180, including lots of the EPROM version.Good chips, with the IAR C Large Model, straight up to 1MB codespace. You just had to choose the bank size to be bigger than your largest function. In those days (1980s) the banking overhead was negligible, since IAR C was so crapWe developed a box converting between IBM coax and twinax, and RS232/Centronics for printer emulation. But other (printer buffer) products sold more, and the Z280 box, with 14 configurable ports, sold so fast we could not make it fast enough. Good days, when a reasonably bright individual could design and sell a product to a general end user applicationOlivetti M24 and M28 were my first "PCs". Never had an IBM one.

author: gatk555
author_rank: Newbie
timestamp: May 01, 2024, 08:25:15 am
content: Surely, any discussion of the Z80's successors should include Captain Zilog:https://archive.computerhistory.org/resources/text/Zilog/Zilog.Z8000.1979.102646293.pdf. (Link button does not work for me.) I recall seeing the paper comic in a small ICL development office in Ealing, London around 1980.

author: coppice
author_rank: Super Contributor
timestamp: May 01, 2024, 11:08:01 am
content: Quote from: peter-h on May 01, 2024, 06:19:49 amIn 1987 Zilog was still launching major things like the Z80000. In 1993 or 94 I remember a friend joining Zilog and the rest of us asking the same question. Why? Zilog was already pretty much dead in the water, and even our friend couldn't give a convincing answer about his move. Such a major downfall, from which they never seemed to recover.

author: brucehoult
author_rank: Super Contributor
timestamp: May 01, 2024, 11:19:37 am
content: Quote from: coppice on May 01, 2024, 11:08:01 amI hope you mean Zilog, not your friend!I was astounded in 2005 when my cousin left Coca Cola to join NZ Yellow Pages -- a company that clear as day was going to get steam-rolled by the internet. Maybe he figured it was just a short term CV builder, and anyway after three years he went to a nice safe museum director position he's now had 15+ years.

author: peter-h
author_rank: Super Contributor
timestamp: May 01, 2024, 02:12:16 pm
content: Mask 1960 was the one with the non-broken UARTQuoteThe Z80k was a great chip, and 1987 was before the Intel domination with the x86. But sentiment is like a tidal wave...I still have somewhere the Z80k C compiler. I believe it was generated entirely with YACCMUFOM tool kit.Maybe Zilog's mistake was to not make microcontrollers. A smaller company must address a smaller and more specialised market - true for any business. And look at today's uC market, with so many players co-existing. People would have gone for a Z80 based uC very readily in say 1990. And it was easy... they had the PIO SIO SCC (85C30) CTC DMA. Just throw them on the same chip. Product designers would have almost no work to do. And the custom CMOS ASIC business was well developed in 1990; I was prototyping ASICs on Xilinx FPGAs, using schematic entry on Viewlogic 4, routing with XACT5, so for Zilog to knock up a uC with all this would have been dead easy. A Z80 is only a few k gates, and would fit in a mid level 1990 FPGA like a XC3090.1976 was hard work for a new uC (the chips were laid out by hand) but 1990 was dead easy.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 01, 2024, 02:25:00 pm
content: Quote from: lunix on April 20, 2024, 06:25:53 amI think that was the Z86<something> - if you turned it upside-down, the pinout was compatible with the PIC16C54. ISTR it was mostly used by people making universal remotes as Zilog had licensed a big library of IR codes & made it available free to anyone using their chip.

author: coppice
author_rank: Super Contributor
timestamp: May 01, 2024, 02:52:12 pm
content: Quote from: peter-h on May 01, 2024, 02:12:16 pmPerhaps, but the market the Z80k was targetting was already dominated by the 68k, with people looking towards things like SPARC to replace it. It had no compelling benefits.Quote from: peter-h on May 01, 2024, 02:12:16 pmThat's true.Quote from: peter-h on May 01, 2024, 02:12:16 pmIt would probably have been uncompetitive in 1990 to throw that stuff in. Gate count was still important, and most MCUs were fine tuned, with every SKU being its own die. Successful peripherals on MCUs didn't usually look that similar to successful peripherals in their own package. Today it would be a no-brainer to throw in the kitchen sink.Quote from: peter-h on May 01, 2024, 02:12:16 pmWow. I see you never worked in MCUs in the early 90s.

author: peter-h
author_rank: Super Contributor
timestamp: May 01, 2024, 03:03:52 pm
content: No but I was doing ASICs of the right sort of gate count. The ASIC business was highly competitive, with sub $1 pricing for 10k+ (yes only 10k!), say 10k gates.I don't know about today but putting a CPU in an FPGA was never competitive.Has a Z80 schematic (or VHDL) ever been published? Various 3rd party ones exist e.g.https://opencores.org/projects/a-z80

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 01, 2024, 09:24:05 pm
content: CPUs on a gate array makes no sense in new designs or where chip cost drives program cost. But if there is a large software investment, or other large one time costs involved it can be a huge cost saving.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 03, 2024, 07:06:25 am
content: Found this, pointed by Hackaday, an open source Z80 in hardware:https://github.com/rejunity/z80-open-siliconhttps://hackaday.com/2024/04/28/the-z80-is-dead-long-live-the-free-z80/

author: peter-h
author_rank: Super Contributor
timestamp: May 03, 2024, 01:06:24 pm
content: Many years ago I was asked to do an FPGA plug-in equivalent for some TMS9900 peripherals. These seemed to have a funny silicon problem in that they all died after some years.The size of the FPGA needed was surprising - something like a (then) Xilinx 3090. Not cheap at about 100 quid.It was also a huge job. I quoted the guy about 20k for the design. He didn't go for it.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 05, 2024, 11:08:30 pm
content: Quote from: RoGeorge on May 03, 2024, 07:06:25 amYes, not sure what the point really is compared to a small-FPGA solution (you only need a pretty entry-level FPGA for implementing a Z80), even with added level shifters if you absolutely need a replacement for existing, vintage products.Or even a software emulation on some moderately powerful MCU can be a solution - with its PIO, I guess that a Z80 could be emulated on a RP2040. You may run into GPIO limitation though. They should definitely release an updated version of it with more GPIOs, an updated PIO and maybe M4-based. That would be a killer.

author: bson
author_rank: Unknown
timestamp: May 05, 2024, 11:46:48 pm
content: Quote from: coppice on May 01, 2024, 01:09:45 amYeah, the 32032 was way too late to market. The 32332 was a significant step up and saw some success though.

author: peter-h
author_rank: Super Contributor
timestamp: May 06, 2024, 07:14:11 am
content: QuoteHas anyone tried it?

author: RoGeorge
author_rank: Super Contributor
timestamp: May 06, 2024, 09:32:02 am
content: There are quite a few Z80 designs for FPGAs already, e.g.:https://opencores.org/projects/a-z80

author: peter-h
author_rank: Super Contributor
timestamp: May 06, 2024, 10:06:11 am
content: Aha I did see that project but on a quick look didn't realise they actually put it in an FPGA.The EP2C20F484C7 is GBP 102and they are using 11% of it. The Spartan-6 6x1s16csg324-2 I could not find. The devkits all list as obsolete.Yes; this is what I found years ago when looking at FPGA versions of the TMS9900 UARTs. Very expensive back then. The UART used up a chunk of a GBP 200 Xilinx 4k FPGA.So to be doing this, you would probably be working on a project which needs a big FPGA anyway, and there aren't many of those. I see things like $5000 ARINC429 interface cards using 3 digit priced FPGAs...It is not efficient to use FPGA logic structure for a design which was totally hard-wired.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 06, 2024, 11:30:58 am
content: Since most of the projects are giving the HDL sources, it means it can be recompiled/ported to any big enough FPGA, older or newer. Z80 is a small CPU, so it should fit in any small/average FPGA. I'll say the design should fit in most $50-$100 FPGA devboards, though I didn't check how big it is exactly.Also, ignore the astronomical prices for FPGAs at Digikey and such, nobody buys them at that price.

author: peter-h
author_rank: Super Contributor
timestamp: May 06, 2024, 06:39:44 pm
content: A couple of rhetorical questions:Can you fit the Z80 into a $5 (100+) FPGA?Since you will still need an EPROM and an SRAM (for 64k address space you won't be using a 8GB DRAM module) you still have a couple of tricky chips to source. EPROMs do exist, just about, FLASH chips definitely exist (but you need to design the PCB for in-circuit programming of a parallel FLASH chip - not trivial, lots of test points for a spring-loaded jig) and SRAMs also exist although only a few vendors nowadays. Can you get a cheap FPGA with say 16k RAM? I had a quick look on Mouser and 16k bytes is pushing it. A few k seems to exist in the $10 range.

author: bson
author_rank: Unknown
timestamp: May 06, 2024, 07:57:26 pm
content: If you want to experiment with a "soft" Z80 on an FPGA, get a quality devkit if you don't have one already, like a Digilent Arty A7-100T. While obviously more expensive than a Z80 it's also not a one-trick pony and can be used for all kinds of future FPGA experimentation and design work. A kit like this will have tons of memory, JTAG, serial port, USB-UART, Shield connector, LEDs, buttons, etc etc. As much as I dislike Arduino, a shield header makes it very easy to add things like an SD card slot.

author: nctnico
author_rank: Super Contributor
timestamp: May 06, 2024, 08:14:23 pm
content: Quote from: peter-h on May 06, 2024, 10:06:11 amA Sipeed tang nano 9k (which uses a low cost FPGA from Gowin) should do it judging from the number of LEs / registers. These FPGAs are pretty cheap and have internal flash and memory so you can build a fully self-contained Z80 system with it. Actually, you can likely have a complete Z80 based home computer like the MSX-2 in a single FPGA..

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 06, 2024, 08:22:07 pm
content: Quote from: peter-h on May 06, 2024, 06:39:44 pmProbably so yes. The T80 core is one of the most used for retro computing stuff, I have toyed with it a bit a few years ago, but it was on a Lattice ECP5 (which, while not expensive, isn't the cheapest FPGA around.) I don't remember how many LUTs it was taking up. But I can look it back up.

author: peter-h
author_rank: Super Contributor
timestamp: May 06, 2024, 09:29:13 pm
content: I am familiar with FPGAs; in 1991-1996 I was doing lots of FPGA design consultancy, some where the FPGA was the end result and then some ASIC prototyping. I used XC3032, XC3064, XC3090, and then some big XC4000 chip (probably XC4062) which I can't remember and which was about £200 but the price didn't matter. The dev tools (Viewlogic/LCA and XACT5) came to £20k, including two donglesToday I have no need for using "FPGAs as FPGAs" since 168MHz+ ARM32 CPUs are so fast and the high level of integration avoids the traditional need for tons of logic. But obviously lots of applications remain otherwise these firms would be out of business.I just wondered if someone could build a Z80 based system with an FPGA which is not ridiculously priced. It might run really fast, too, in the new devices.

author: MarkL
author_rank: Unknown
timestamp: May 06, 2024, 10:18:20 pm
content: I thought this was an interesting board:http://www.s100computers.com/My%20System%20Pages/FPGA%20Z80%20SBC/FPGA%20Z80%20SBC.htmAnyone have any experience with it?

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 06, 2024, 10:29:08 pm
content: Prices for FPGAs and their dev tools have obviously dropped dramatically since the 90's (except for the very high-end FPGAs which are absolute monsters).I've looked back at my project, the T80 core was taking about 2700 LUT4s.That would fit no problem in many entry-level FPGAs which cost just a few bucks.https://opencores.org/projects/t80/

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 07, 2024, 12:18:40 am
content: Quote from: peter-h on May 06, 2024, 06:39:44 pmThat's the challenge, in all these FPGA variants : How far do you clone the original architectures ?If you wanted to clone EPROM and SRAM, you likely also want 5V operation ? That's even messier on modern FPGA'sIf you just need 'binary compatible', does that need to be cycle precise, or is faster in a straight line ok ?As you say, parallel memories are fading, but there are new QSPI SRAM parts that could work well with a FPGA core.eg Microchip's recent QSPI 23LCV04M 4MBit can burst up to 143Mhz

author: gnuarm
author_rank: Super Contributor
timestamp: May 07, 2024, 04:40:19 am
content: Quote from: coppice on April 21, 2024, 12:07:56 pmfunny about the timing thing. The machine cycle timing came originally from the 8008 in an 18 pin package. Because of the small pin count, they muxed 8 pins as two clock cycles of upper and lower address and a third clock cycle for the data transfer. This should have allowed a DRAM interface without any multiplexing logic (which is lots of pins).The 8080 used the same machine cycles, even though there were 24 pins for separate address and data buses. I believe the Z80 also used the same machine cycles, if I'm not mistaken.I don't recall all that much compatibility between different brands of DRAM. They mostly operated the same, but detail timings were often different as they tried to outperform each other. Speed was a big deal at the time with both capacity and speed improving significantly each few months.Then they started using different interfaces, DDR and such. One company got the standards organization to standardize their proprietary interface, RAMBUS, I think it was. Then, everyone found RAMBUS wanted them to pay license fees!!! The crap hit the fan, and everyone was held back until they could spin a new DDRx generation. I think ultimately, RAMBUS didn't do so well.

author: gnuarm
author_rank: Super Contributor
timestamp: May 07, 2024, 04:47:44 am
content: Quote from: SiliconWizard on May 06, 2024, 08:22:07 pmThe Lattice ICE stuff is much cheaper, but without some of the bells and whistles. The BRAM is only x8 rather than x9 bits wide. That ninth bit can be useful. Heck, some of the Xilinx parts are pretty affordable too.I stopped using standard MCU cores some time back. I roll my own, stack based CPUs. They can be optimized to run pretty quickly, since the logic path is rather streamlined. They are called MISC for Minimal Instruction Set Computers. They can have opcodes as small as 4 bits. This also helps to facilitate fast clock cycles, and use very low LUT counts.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 07, 2024, 05:36:16 am
content: Classic Z80 was 40 pins DIL, with full 8 bit data bus and full 16 bit address bus, plus a few more lines for the control bus.Has only a few registers, some of them doubled as an alternate set.http://www.zilog.com/docs/z80/um0080.pdfLess than 10 thousand transistors in total (8500). No RAM and no EPROM internally, but could generate transparent refresh cycles in case the RAM was DRAM. Otherwise, the CPU was entirely static. Clock, at first was 2.5MHz, or 4MHz, sometimes 6MHz, but later it went faster.The 4MHz ones were heaving some margin for overclocking.I've found a few 4MHz that were running stable at 7MHz, simply by binning the fastest one. No extra cooling, though lowering the 5V for the entire system just a little, at about 4.7V, was helping with stability.

author: peter-h
author_rank: Super Contributor
timestamp: May 07, 2024, 07:39:44 pm
content: The original Z80 was not static. The later CMOS versions were, starting the Nat Semi NSC800https://www.cryptomuseum.com/spy/fs5000/files/NSC800.pdf

author: Howardlong
author_rank: Super Contributor
timestamp: June 02, 2024, 10:57:28 am
content: Quote from: RoGeorge on May 07, 2024, 05:36:16 amTransparent in terms of cycles. Not so "transparent" in terms of the glue logic and timing hacks required to satisfy the day's DRAM timings!All it is is a counter that exposes itself on the address bus on the second half of an M1 cycle.Of interest was that while the R register is exposed on the lower half of the address bus, the I register is exposed on A8-A15 when \RFSH is asserted. Despite not using DRAM, this undocumented feature was used by Sinclair in their ZX80 and/or ZX81 (I can't remember which one, it might have been both) as part of a crude CRTC: during the horizontal blanking period there was just enough time for a tiny bit of code to run that updated the I register appropriately. The auto-incrementing R register was used as the character count, and the I register as the character row scan count and the address in ROM of the character generator. The intricate details I've forgotten, but this was as a result of reverse engineering it when I was a spotty teenager. I remember calling Zilog to ask them if this was a supported feature, and the answer was "no".

author: iMo
author_rank: Super Contributor
timestamp: June 02, 2024, 02:12:14 pm
content: Imho, the ice40up5k would be a nice target for a Z80 system (15kB bram and 128kB psram).20MHz clock should be achievable..

author: brucehoult
author_rank: Super Contributor
timestamp: June 02, 2024, 04:01:46 pm
content: Quote from: iMo on June 02, 2024, 02:12:14 pm20 MHz clock with original z80 4-20+ cycles per instruction? That's pretty awful.There are RISC-V implementations that fit on ice40up5k and do single-cycle (32 bit!) execution at 24 MHz on straight line code, less than 2 CPI on typical branchy/loopy code e.g. 17 DMIPS (0.7/MHz, typical of result bypass but no branch prediction)z80 does 0.042 DMIPS/MHz when compiled with modern SDCC.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 02, 2024, 09:56:18 pm
content: Quote from: iMo on June 02, 2024, 02:12:14 pmYeah. I've tried the T80 core on a Lattice ECP5 and timing was achieving over 50MHz. It's probably going to be lower on a iCE40UP. 20MHz should be achievable. I might test that when I get the time, just out of curiosity.And it's probably possible to do better than the T80 in terms of implementation. It's just that it's a proven design.

author: Picuino
author_rank: Super Contributor
timestamp: June 03, 2024, 07:16:47 pm
content: Z80 is the microcontroller of my first two computers (a CPM computer and a Spectrum), the first assembly language I learned and the first microprocessor I studied.It has truly had a long life. This news makes those of my generation a little older.

author: jzx
author_rank: Regular Contributor
timestamp: June 04, 2024, 04:24:16 pm
content: Quote from: Howardlong on June 02, 2024, 10:57:28 amBoth ZX80 and ZX81 use almost the same system, but the ZX81 uses also the NMI for "multitasking", that is, it can do at same time display and your program, the ZX80 only can do user program OR display.They do not use the IR for adressring, they EXECUTE the video memory, literally, but the circuitry stoles the opcodes (characters actually) and subtitutes with NOPs, and while the refresh period, the external circuitry puts the character code (6 bits), and a scanline counter (3 bits) in the address bus, and the remaining high bits (7) are from the I register, and then a shift register load the video bits from the character generator in the ROM. Very convoluted.But in the "new" High Resolution Graphics" mode, I and R are used as the bitmapped graphics address, because some people discovered that the address modification made by the ULA does not work on external memory, and allowed for something not oficially possible.In the ZX80-ZX81 the R register is used as a sort of timer or watchdog. The A6 line is directly connected to INT, that seems very bizarre, but the Z80 checks INT while refreshing, this way in every line the video routines load R with an apropiate number and when the time has elapsed, cut the video routine.You have in the ZX80/81 expansion slot both, A6 and INT, but they are shorted

author: jzx
author_rank: Regular Contributor
timestamp: June 04, 2024, 04:35:53 pm
content: More details, (not by me)https://web.archive.org/web/20201108114958/http://www.user.dccnet.com/wrigter/index_files/ZX%20Video%20Tutorial.htm

author: obiwanjacobi
author_rank: Super Contributor
timestamp: June 06, 2024, 08:18:05 am
content: C9

author: iMo
author_rank: Super Contributor
timestamp: June 11, 2024, 09:55:18 am
content: FYIhttps://github.com/rejunity/z80-open-silicon

author: iMo
author_rank: Super Contributor
timestamp: June 11, 2024, 10:09:35 am
content: Quote from: brucehoult on June 02, 2024, 04:01:46 pmYep, I ran here the"RudoIV"risc-v on the 40up5k/UPduino (the userland C bincode ran off the onchip 128kb spram loaded from the bitstream flash, yosys tools), and the max was 20-24MHz clock as I can remember.. The iCe40UP family is rather slow, a pity..

author: bson
author_rank: Unknown
timestamp: June 12, 2024, 07:20:03 pm
content: Quote from: iMo on June 11, 2024, 09:55:18 amThat's really neat. Especially if it can also run on 3.3V and be had as a naked QFN64! That would allow for a SUPER compact little CP/M-80 SBC.

author: Mike8080
author_rank: Newbie
timestamp: June 14, 2024, 11:20:09 pm
content: I wired up an S-100 Z-80 computer (Vector wiring pencil) WBW (way back when). Memory was 4k x 1 dynamic RAM that I blowtorched off of some surplus boards that had their gold edge connectors sliced off to recycle the gold. I could fit 32 of the chips on an S-100 board, so 16kbytes on each board. Good times!

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 14, 2024, 11:51:59 pm
content: Quote from: bson on June 12, 2024, 07:20:03 pmFrankly, I still don't see much point, if you want to do that, compared to a soft core on a small FPGA.And if you absolutely want a 'hard" core, then the Z180, which is largely compatible with the Z80, but improved, is still available, for instance at Digikey. It may not be a safe bet if you plan a high-volume series for years to come, as it's EOL, but there's still stock.And if you just want to design a small CP/M 80 SBC just for the heck of it with no particular care for being 5V, nor being cycle-accurate, you can even just emulate it on a RP2040 for $1.You have an example here (among a bunch actually):https://github.com/ExtremeElectronics/RC2040

author: woofy
author_rank: Frequent Contributor
timestamp: June 16, 2024, 07:06:47 pm
content: The Z80 CPU - 1976 to 2024https://youtu.be/cbMdq8Dsz6Y?si=Vs8dKGGsZVIWotgn

author: bson
author_rank: Unknown
timestamp: June 16, 2024, 08:02:21 pm
content: Quote from: SiliconWizard on June 14, 2024, 11:51:59 pmIt's just for fun, to remind myself of the bus timings, etc. Any CMOS SMT version would work just as well. I don't have any actual use for it.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 16, 2024, 08:46:56 pm
content: Quote from: bson on June 16, 2024, 08:02:21 pmThen you shouldn't have any problem buying a bunch of real Z80's, which can still be bought from various places. And the Z180, again, which is in stock at Digikey.You probably misunderstood my point: I didn't say there was no point in working with real hardware, if you're interested in that.I just said that for this, actual parts are still available, so what I don't see is the point of going as far as designing brand new silicon for that. Doesn't make sense.Just buy a couple Z80s (probably on Ali or eBay), or Z180s (Digikey, I think Mouser has some as well), and start hacking away!

author: bson
author_rank: Unknown
timestamp: June 18, 2024, 05:38:05 pm
content: Quote from: SiliconWizard on June 16, 2024, 08:46:56 pmThis is true, but being part of a community effort still tickles something positively, psychologically speaking, that a commercial part can't. Since it's purely for fun this is a non-negligible aspect.

author: RoGeorge
author_rank: Super Contributor
timestamp: June 18, 2024, 06:01:10 pm
content: Many microcontrollers today can emulate a Z80 almost flawless. Only a few days ago I've seen an entire Sinclair ZX Spectrum home computer emulated with an ESP32:https://hackaday.com/2024/06/16/esp32-powers-single-pcb-zx-spectrum-emulator/

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: June 18, 2024, 06:36:55 pm
content: Digi International makes a series of MCUs called the Rabbit which include a Z80 clone.https://www.digi.com/products/embedded-systems/digi-connectcore/system-on-modules/rcm3000

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 19, 2024, 01:53:15 am
content: Quote from: bson on June 18, 2024, 05:38:05 pmWell, certainly, I was speaking from a purely pragmatic POV, but if people want to design a brand new Z80 on silicon, I'm nobody to say they shouldn't!But since this all has a significant cost, I think it's in their best interest to make sure they know all their options before investing time and money in that. Also a bit wary of the "hype" effect triggered by the EOL announcement, that may fade off in a few months from now, before the project actually gets completed. We'll see.

author: zapta
author_rank: Super Contributor
timestamp: June 25, 2024, 04:58:48 pm
content: 1k resistor outlast the z80. What a shame.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 28, 2024, 05:48:30 am
content: Just thought I forgot to mention the eZ80, which is still in production, Littelfuse has no intention to stop producing it, and should be binary-compatible with the Z80 while adding tons of features and being much, much faster. Still used in some TI calculators AFAIK.So if one wants to build a Z80 board for various purposes including running CP/M on real Zilog hardware, then that would be it IMO. Still easily available everywhere.

author: woofy
author_rank: Frequent Contributor
timestamp: June 28, 2024, 08:24:15 am
content: For me the only reason to use a Z80 is to scratch a nostalgic itch, and that's what I did a couple of years ago. An FPGA was used to mop up all the random logic, memory mapping, interrupt logic, vga, that sort of thing. I could have put the Z80 into the fpga, but no. That would not scratch the itch, it had to be a real Z80. A look-a-like chip eZ80, 64180, fpga or whatever just would not do.I must be getting old, nostalgia isn't what it used to be.

author: westfw
author_rank: Super Contributor
timestamp: July 09, 2024, 09:50:28 pm
content: Don't some vendors other than Zilog make "Z80 compatible" chips?Are they all also going to stop producing them?Ebay listing: "Z80 compatible CPU. New, from Russia." (like Nixies!)

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 09, 2024, 11:37:05 pm
content: I know this has made a lot of "RIP Z80" videos, and the "hype" will pass, and soon enough no one will be talking about the Z80 anymore, at least no more than just a few months ago.Littlefuse, who owns Zilog, has made a clear statement about the why: there is not much market for original Z80 parts anymore, which is a dog by today's standards, and they had to maintain a 4µm process node just for this chip. Crazy. They should have pulled the plug earlier.As I already said, there are newer, "compatible" Z80 parts, that Littelfuse has been clear about keeping production lines for. On more modern process nodes, and not 5V anymore, but who needs that anymore except hobbyists keen on vintage stuff? Why would companies bother making 5V clones for a market that would never repay the investment?To me it all really looks like yet again one of these hype waves, that triggers a frenzy about something that people otherwise mostly didn't care about, and that will pass as quickly as it started, probably as soon as Youtubers will be tired of making retrospective Z80 videos. Just my 2 cents anyway.

author: brucehoult
author_rank: Super Contributor
timestamp: July 10, 2024, 02:06:22 am
content: Quote from: SiliconWizard on July 09, 2024, 11:37:05 pmDo they only have the original hand-drawn masks and not a net list?TSMC's 130nm and 180nm nodes (for example) are both 5V compatible. Fully-automated layout from a net list would probably get you a 200 MHz part.Personally I'm just glad I don't have to do anything serious with either the 6502 or z80 any more. Both are just absolutely horrid. If you need 8 bit then AVR is infinitely nicer, MSP430 for 16 bit (which is pretty pointless these days), or RV32EC or Cotex-M0 for tiny 32 bit cores.CH32V003 (2k RAM, 16k flash, 48 MHz) is 1732x1172 µm. I found numbers for MSP430FR5738 (1k RAM, 16k FRAM, 24 MHz) of 2280x2080 µm, 2.3 times bigger. z80 is 3545×3350 μm. 6502 is 3890x4270 μm and would be called 5μm today (the very first ones were I think 8μm).

author: coppice
author_rank: Super Contributor
timestamp: July 10, 2024, 01:30:14 pm
content: Quote from: brucehoult on July 10, 2024, 02:06:22 amTSMC's 130nm and 180nm nodes are 5V I/O compatible, but doing the core in the big 5V I/O transistors would made the part large and slow. You won't get to anything like 200MHz unless you go to the complexity of split supplies.