hybridfree/eevblog-posts huggingface dataset:
A SBus card for SPARCstation designed in 2020... - Page 1
Forum section: electronics / general

author: dolbeau
author_rank: Regular Contributor
timestamp: December 12, 2020, 06:08:01 pm
content: Hello,Thanks to the help found in these forums, my insane project is now somewhat working. I've made a SBus card featuring an Artix-7 FGPA for my 90's SPARCstations :-)To be more accurate, it's a SBus adapter board that takes on a commercial board (ZTex USB-FPGA Module 2.13, as designing the whole thing was way too complicated - it's my first hardware design...Things are still very rough. If the board tries to initialize early (so it can be seen during POST), the SPARCstation 20 I use won't POST reliably. If I delay the start-up by 20s (hot-plugging also work, but it's probably a better idea to just delay the init ;-) ) , enough for the SS20 to POST and reach the OpenBoot prompt, then I can force a discovery of the board. It will then appear in the device tree - OpenBoot can read my minimalist ROM. I can then map my board's internal 'registers' in virtual memory, letting me write to them from OpenBoot to e.g. change how the board LEDs blink. I'm also able to do some GCM computations in the FPGA from OpenBoot. Next step, doing GCM from inside NetBSD to create a crypto accelerator :-)Extract from the device tree as seen by NetBSD:Code:ss20:~> sudo ofctl -l | egrep 'SPARC|iommu|sbus|FPGA'ffd4e630: /SUNW,SPARCstation-20ffd5b700: /iommu@f,e0000000ffd5b890: /sbus@f,e0001000ffd76fb0: /RDOL,SBusFPGA@1,200But no driver yet:Code:ss20:~> sudo dmesg | grep -C1 FPGA[ 1.000006] dbri0 at sbus0 slot 14 offset 0x10000 level 9: rev e[ 1.000006] RDOL,SBusFPGA at sbus0 slot 1 offset 0x200 not configured[ 1.000006] cgsix0 at sbus0 slot 2 offset 0x0 level 9: SUNW,501-2325, 1152 x 900, rev 11 (console)And a couple of picture. The blue part is a 3D-printed extension to meet the physical requirements (smaller PCBs are cheaper!), the small transversal board on top is the Ztex. On the left are the 96 solder point for the SBus connector and the level shifters (SBus is 5V...), on the right a header for a serial port, JTAG (untested) and micro-sd (untested) and some LEDs in the middle (10 in all).In the 'live' picture, the fuzzy beaglebone white (top left) is connected by jumper cable to the serial header (one-way) to see the trace of the SBus FSM that my design emit for debugging.

author: dolbeau
author_rank: Regular Contributor
timestamp: December 13, 2020, 02:16:30 pm
content: Everything is now there:https://github.com/rdolbeau/SBusFPGA

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 13, 2020, 02:30:43 pm
content: Neat, it works!Tim

author: dolbeau
author_rank: Regular Contributor
timestamp: December 13, 2020, 06:47:13 pm
content: Quote from: T3sl4co1l on December 13, 2020, 02:30:43 pmYes - and probably wouldn't have without the help from this forum !Still a long way from doing something useful with it, but both the PROM and OS see and talk to the FPGA, so the now it's a matter of gateware & driver mostly...
Advantage of using the DEN and DTR control signals on an 8088? - Page 1
Forum section: electronics / general

author: David00
author_rank: Contributor
timestamp: November 25, 2020, 02:57:37 pm
content: What is the advantage of using the DEN and DTR control signals on an 8088? The question isn't as simple as it sounds.The answer isn’t “they enable and control the direction of a bus transceiver, such as an 8286 or 74245”. I know that’s their stated purpose.While some 8088-based systems use DTR and DEN, there are several that don’t and rely just on RD and WR.I’m familiar with the cycle timing of these signals, and that for a Read operation DEN goes high at the end of T3 and RD goes high a quarter of the way into T4. For a Write operation it’s reversed with WR going high at the end of T3 and DEN going high a quarter of the way into T4. But what is the benefit of this slight timing difference?Why wouldn't a bus transceiver simply use RD (plus INTA) and WR to control its operation? That may answer my original question - what advantage does DTR and DEN give over RD and WR?

author: ebastler
author_rank: Super Contributor
timestamp: November 27, 2020, 04:01:18 pm
content: Seems like the use of DT/R buys you some time, e.g. for use with slower bus transceivers? By the time the R or W signal reaches the peripherals on the data bus, the transceiver has had some time to set up the data lines?

author: David00
author_rank: Contributor
timestamp: November 27, 2020, 11:57:11 pm
content: @ebastler. Thanks for the suggestion, but the cycle timing doesn’t support that theory.To clarify, the transceiver (or similar circuitry) enable (DEN equivalent) is generated at a basic level by ORing RD and WR, and the direction is controlled by RD.I think the issue is at the tail end of the cycle. There’s no problem with a Read operation as the CPU has sampled the data before both DEN and RD have gone high.But for a Write operation, a logic or memory device can’t sample/output within a clock cycle like the CPU can. It has to wait for WR to go high then it captures the data it sees at the transceiver. If WR is also being used to control the transceiver, at the point that it is telling the device to capture the data it is also telling the transceiver to tri-state its output.I’m coming to the conclusion that a RD-WR controlled system only works if it is enabled for a fraction longer than the WR strobe to the device it is writing to, perhaps by additional gate delays within logic driving it.
Why are ALE and INTA not floated during Hold on an 8088 while other outputs are? - Page 1
Forum section: electronics / general

author: David00
author_rank: Contributor
timestamp: November 26, 2020, 07:10:08 pm
content: When the 8088 goes into hold, every output is tri-stated apart from HLDA (obviously), ALE and INTA. Given that the purpose of hold is to allow an external device to control the bus, like a DMA controller, what's the rationale behind ALE and INTA still being driven?I think I partly know the answer to this:If INTA wasn't driven high, it might float low and accidentally cause an interrupt vector to be placed onto the data bus causing contention.If ALE wasn't driven low, it might float high and accidentally latch some spurious low-order address data, so that when the CPU came out of hold then A0..A7 would be incorrect. But this wouldn't matter, would it? As after exiting hold the next instruction's T1 cycle would cause the correct low-order address lines to be latched.Is it simply that ALE doesn't NEED to be tri-stated, so this capability wasn't added by Intel?
Nintendo Entertainment System repair help please! - Page 1
Forum section: electronics / general

author: alank2
author_rank: Super Contributor
timestamp: November 25, 2020, 07:14:16 pm
content: I was having a problem with cartridges not working and they were real sticky trying to push them in or pull them out so I opened up an original nintendo entertainment system to find it had a bit of what looks like dirt/mud that somehow got into it. I cleaned the contacts on the 72-pin connector, took it all apart, washed it out, rinsed the board carefully, and blasted it with compressed air and got it back together. This improved the sticky issue with the cartridge, but it didn't always work when inserting cartridges so I thought perhaps I needed to also lift the pins on the connector which I skipped because they did seem high enough to me already. Took it apart, lifted the pins, and then noticed I hadn't put the underside of the RF area metal case back on it the first time, at this point it is not plugged into anything and I go to put the small 2" x 2" plate back on and somehow it comes into contact with a solder joint and I see a small arc/short occur. There is a 2200uF cap on it which rectifies an 8 VAC loaded signal coming in from the wall adapter so I have to presume that it is one of its leads that shorted to ground. I finish putting it together and now here is no composite video output. I tried different cartridges and still no video. Sometimes the red light blinks which i think is some sort of protection thing, and sometimes not. I disable the protection chip by cutting pin 4, still no video. I take it all apart and look at the video pin going to the RF module, it has very little voltage on it when powered on (somewhere between 0-.3 V), but no signal of any type on the scope. I pulled the transistor connected to the video line on the RF module thinking maybe it was zapped and loading down the video signal, but it tests okay when pulled so I put it back. Voltages seem mostly good, the voltage regulator outputs 5V when powered on and the IC's are getting it. Sometimes I see a sawtooth type pattern on it, but I don't think that is related to it not working, but maybe that the heat sink is getting too warm not being connected to any of the metal shields. I looked at pin 21 coming out of the non CPU IC because I saw a schematic where it showed this was video out, same thing, no signal.I don't know if it is supposed to put out a video signal even with no cartridge inserted, so that is one problem, perhaps my 72 pin connector is really the problem and it just can't read a cartridge, but I wonder if the short I saw did something, maybe even allowed a negative voltage spike to ground which damaged an IC or something.I saw a test point oscilloscope thing for the NES on a site, but it doesn't mentione where the test points are and I don't see anything labeled on the PCB either.Any thoughts on what to look at next?
This is where your MOS chips were made... - Page 1
Forum section: electronics / general

author: Bud
author_rank: Super Contributor
timestamp: November 23, 2020, 06:14:43 pm
content: Bill Herd of Commodore on a final visit of his former place of work, the MOS office , chip design and production fab:https://youtu.be/OI20uSRtJUU

author: rsjsouza
author_rank: Super Contributor
timestamp: November 23, 2020, 06:29:28 pm
content: Thanks. Bookmarked for later.

author: ebastler
author_rank: Super Contributor
timestamp: November 23, 2020, 07:21:49 pm
content: Made me dizzy watching, but I learnt something: You are supposed to pronounce them "Em-Oh-Ess Technologies", not "Moss" as I am prone to say.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 24, 2020, 02:59:46 pm
content: Quote from: ebastler on November 23, 2020, 07:21:49 pmIn the same vein, I used to pronounce ARM letter by letter until just a few years ago, at which point I finally pronounced it "arm" as most do these days. I don't remember how people at ARM used to really pronounce it in the old days.
Are onboard RAM words tested on Macintosh Classic II P.O.S.T? - Page 1
Forum section: electronics / general

author: gkmaia
author_rank: Frequent Contributor
timestamp: August 01, 2020, 07:50:10 am
content: Are onboard RAM words tested on Classic II P.O.S.T?If they are not is there a software that tests all onboard RAM words? Compatible with Mac OS7.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: August 10, 2020, 11:34:47 am
content: Quote from: gkmaia on August 01, 2020, 07:50:10 amYes. You will notice that when you add more RAM, POST takes longer. Can't remember what happens if the test fails though.

author: kripton2035
author_rank: Super Contributor
timestamp: August 10, 2020, 11:39:41 am
content: you get a normal boot "beep" if POST succeeds. or no sound if it fails. or sometimes the broken glass sound.

author: tooki
author_rank: Super Contributor
timestamp: October 12, 2020, 02:43:40 pm
content: All classic Macs perform basic RAM tests on startup. The startup chime is the result of a successful POST.The failure sound, the "chimes of death", varies by model.(To this day, I think the startup chime on the NuBus Power Macs, the 6100/7100/8100, is the coolest one they ever used. 00:17 in the video. That and the Twentieth Anniversary Mac, 00:30.)

author: kripton2035
author_rank: Super Contributor
timestamp: October 12, 2020, 05:30:53 pm
content: and on recent machines, that have no beep at startup, the post succeeds if and only if the screen backlight goes on.

author: tooki
author_rank: Super Contributor
timestamp: October 13, 2020, 08:22:00 am
content: Quote from: kripton2035 on October 12, 2020, 05:30:53 pmNo, the startup chime is merely disabled by default on newer Macs. The video above includes the new startup chime on the latest Macs.What they do lack is error beep codes if POST fails.
IBM mainframe and server CPUs - Page 1
Forum section: electronics / general

author: Bud
author_rank: Super Contributor
timestamp: November 04, 2018, 04:02:42 am
content: Big ass IBM CPUs in the first and last 30 seconds of the video, some with heatsinks

author: Bud
author_rank: Super Contributor
timestamp: November 04, 2018, 05:14:50 am
content: More mainframe CPU porn

author: Ampera
author_rank: Super Contributor
timestamp: November 04, 2018, 07:19:29 am
content: Starting to look like silicon pizza!

author: German_EE
author_rank: Super Contributor
timestamp: November 04, 2018, 08:22:32 am
content: I still can't get used to the idea of mainframes with a removable CPU. Back when I was a lad (yeah, I know) if you wanted to move the CPU you disconnected the cooling pipes and the data cables then used a forklift to relocate the cabinet.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 05, 2018, 06:46:33 pm
content: I remember those blue IBM Ramdacs on the Imagine 2 VGA cards.

author: TheEPROM9
author_rank: Frequent Contributor
timestamp: November 05, 2018, 10:15:53 pm
content: Quote from: Bud on November 04, 2018, 04:02:42 amThat is on nice colection, gives me an idea of what I should do when i get my own place.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 05, 2018, 10:22:31 pm
content: In that video thumbnail the colours and shine on them remind of me jewellery.

author: nad007007
author_rank: Contributor
timestamp: March 08, 2019, 09:00:03 am
content: Very nice

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 07, 2020, 03:14:50 am
content: This is a badass collection, for sure.

author: intabits
author_rank: Frequent Contributor
timestamp: October 08, 2020, 08:36:57 am
content: My video of one of these beasts:-https://www.eevblog.com/forum/vintage-computing/ibm-9121-thermal-conduction-module-teardown/msg1523362/#msg1523362
Altair 8800 lookalike operator panel? - Page 1
Forum section: electronics / general

author: MathematicalJ
author_rank: Contributor
timestamp: October 08, 2020, 04:06:42 pm
content: I happened acrossthis eBay listing (not mine) for an industrial operator panel, and it looks extremely similar to the Altair 8800 front panel. I assume this kind of panel interface was common in the '70s? What other well-known machines have this same interface?

author: DrG
author_rank: Super Contributor
timestamp: October 08, 2020, 06:15:42 pm
content: Quote from: MathematicalJ on October 08, 2020, 04:06:42 pmTake a look at the Altair 8800 front panel: [courtesy ofhttps://americanhistory.si.edu/collections/search/object/nmah_334396]Not sure why you would call that "extremely similar". Having address and data bus indicators and toggles (what I would loosely call them) on a front panel was not uncommon in an earlier time. I remember having to toggle in reboot code on PDP/8E, it was not a pleasant memory

author: Stray Electron
author_rank: Super Contributor
timestamp: October 08, 2020, 06:55:57 pm
content: Quote from: MathematicalJ on October 08, 2020, 04:06:42 pmA panel with some lights and switches, that's where the similarity ends! $368! The seller has been doing to many drugs!
Corona Data Systems PC-400 quick look  - Page 1
Forum section: electronics / general

author: intabits
author_rank: Frequent Contributor
timestamp: October 08, 2020, 08:27:30 am
content: A quick look inside a Corona Data Systems PC-400. A desktop model of an early IBM PC clone/compatible, made in 1983.Manual link:-ftp://ftp.oldskool.org/pub/drivers/Corona/PPC-400-22/Corona%20Data%20Systems%20PC-400%20PPC-400%20User%27s%20Guide%20PC%20Tutor%202.0%20GWBASIC%202.0.pdf
VWestlife's video on using IBM PC with a cassette recorder features Dave - Page 1
Forum section: electronics / general

author: Zbig
author_rank: Frequent Contributor
timestamp: October 06, 2020, 01:55:33 pm
content: One of the Dave's snarky remarks got featured in the VWestlife's latest video on using a cassette recorder with IBM PC and it's hilariousI purposely won't provide just the exact timestamp as I think the whole thing is well worth the watch:And there's more than this one funny reference

author: Tomorokoshi
author_rank: Super Contributor
timestamp: October 06, 2020, 04:03:41 pm
content: That reminds me that I need to repair my CCR-82.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: October 06, 2020, 04:14:35 pm
content: Daisy? Dave? IBM? Hmm...
PDP8/A - Quick look and Teardown - Page 1
Forum section: electronics / general

author: intabits
author_rank: Frequent Contributor
timestamp: September 23, 2020, 08:39:22 am
content: Even though none of them are yet operational, I've been messing about with PDP-11s for long enough now.It's time to have a quick look at my PDP-8s, starting with the PDP-8/A.

author: DrG
author_rank: Super Contributor
timestamp: September 23, 2020, 04:14:41 pm
content: Quote from: intabits on September 23, 2020, 08:39:22 amThat disk cartridge at ~55"...I have one as a wall hanging

author: intabits
author_rank: Frequent Contributor
timestamp: September 23, 2020, 08:38:03 pm
content: Quote from: DrG on September 23, 2020, 04:14:41 pmAnd it comes with a bonus headcrash!I might have one too. One of mine says "do not use"...
Help with my ridiculous quest - Page 1
Forum section: electronics / general

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 29, 2020, 04:53:07 am
content: I want to add 256K to my Commodore 64's expansion card. Usually I get 8 41256 chips of the same brand and access speed.I have no complete sets of 8 identical 41256 chips.So I decided to go the opposite, I want 8 different brands. So far I have a Mitsubishi, Samsung, Fujitsu, TI, and the dreaded MT.Does anyone know if MT ever got their act together or are 41256s as unreliable as their 4164s?Also what other brands exist? OKI? Siemens? Hitachi? Anything else?Edit: ooooh, maybe there are some Eastern Bloc clones??

author: gslick
author_rank: Frequent Contributor
timestamp: October 01, 2020, 12:14:23 am
content: http://www.minuszerodegrees.net/memory/41256.htmAustin AS4C1259Fujitsu MB81256GoldStar GM71256 / GM71C256AHitachi HM50256 / HM51256P / HM51256LPHyundai HY53C256L / HY53C256LSIntel P21256 / P51C256HMicron MT1256 / MT1259Mitsubishi M5M4256P / M5M4256AP / M5M4256SMosel MS51256Motorola MCM6256 / MCM6256BPNational Semiconductor NMC41256NEC µPD41256C / µPD41256DOki MSM41256 / MSM41256A / MSM51C256Panasonic / Matsushita MN41256 / MN41256ASamsung KM41256 / KM41256AP / KM41C256PSanyo LM33256Sharp LH21256Siemens HYB41256TI TMS4256Thomson MKB45F56PToshiba TMM41256P / TMM41256AP / TC51256PVitelic V53C256 / V53C256AP
1990 80C32 Board - Page 1
Forum section: electronics / general

author: DrG
author_rank: Super Contributor
timestamp: September 19, 2020, 03:08:05 pm
content: Hard to believe it is ~30 years old (not sure why that is hard to believe.Coming across it, I thought, Oh wow, I will get it working and put it in a nice case and go burn a BASIC and build a little terminal board with display (this fellow did a really nice jobhttps://geoffg.net/terminal.html)....and then ___________I don't know about any of that, but I may see if it will power up

author: DrG
author_rank: Super Contributor
timestamp: September 19, 2020, 07:39:18 pm
content: It's Alive! Nice.

author: Bruce Abbott
author_rank: Frequent Contributor
timestamp: September 22, 2020, 09:10:22 pm
content: Any chance of getting a ROM dump?BTW here's an advert for that board in Circuit Cellar April/May 1991:-

author: Kjelt
author_rank: Super Contributor
timestamp: September 22, 2020, 09:19:17 pm
content: Brings back memories.Seeing that it remains hard to believe that nowadays everything you see on that board except psu and battery is integrated in an couple of square mm microcontroller.

author: DrG
author_rank: Super Contributor
timestamp: September 23, 2020, 04:01:11 pm
content: Quote from: Bruce Abbott on September 22, 2020, 09:10:22 pmThanks so much for the advert reference - I love that stuff. Sorry, but I don't want to post a ROM dump.
Cleaning vintage circuit boards - Page 1
Forum section: electronics / general

author: smbaker
author_rank: Regular Contributor
timestamp: September 30, 2020, 08:21:30 am
content: I have a heathkit trainer that I recently acquired that could use a little bit of cleaning. These trainers are a white PCB with some silkscreen printed on it (in this case in blue). This particular trainer came from Florida. What I assumed to be simple dust actually seems to be quite embedded in the white surface of the PCB. My first thought was to try to clean it off with isopropyl alcohol, but it seems like this: 1) does a lousy job of cleaning, and 2) does a decent job of removing the blue silkscreen.What seemed to be working a little better is a pencil eraser, so failing any better suggestions I might give that a go (would need to find a few precision erasers to get into the nooks and crannies).Was curious if anyone had a better idea.Scott

author: Bud
author_rank: Super Contributor
timestamp: September 30, 2020, 12:35:23 pm
content: I can think of Spray Nine or WD40.

author: ebastler
author_rank: Super Contributor
timestamp: September 30, 2020, 06:07:27 pm
content: Have you tried water and dishwashing detergent?Try carefully with a wetted sponge first. If that does not attack the silkscreen, use water with detergent generously, even immersing the whole board unless it has specific components which speak against that. Carefully apply a sponge or toothbrush for extra cleaning action if needed. Robust natures recommend a cycle in the dishwasher for stubborn cases; I have never tried that personally though.Rinse well; rinse with demineralized water if you want to be extra-diligent. Dry in a warm place, so the moisture does not stay in the nooks and crannies for too long.

author: james_s
author_rank: Super Contributor
timestamp: September 30, 2020, 06:55:57 pm
content: I scrub PCBs with warm water and a bit of liquid dish soap, use a soft bristled brush to scrub off the dirt then rinse thoroughly. If your water has a high mineral content consider rinsing with distilled water but that is not necessary where I am. When finished stand it up on edge and allow it to dry for a couple of days.

author: Haenk
author_rank: Super Contributor
timestamp: October 02, 2020, 12:15:17 pm
content: Warm water from the tap and a very soft sponge with detergent is my method of choice, you just need to let it dry for quite a whileHowever check for stuff that might get damaged *before*, like relays.
PDP11/05  - Quick look and Teardown - Page 1
Forum section: electronics / general

author: intabits
author_rank: Frequent Contributor
timestamp: September 23, 2020, 02:42:07 am
content: A quick look inside a DEC PDP11/05, made in Ireland back in about 1973.The power supply has some bad electrolytic capacitors, so power on and tryout will have to wait until they have been replaced.
PowEredge R620/R720 daughter card connector and/or pinout? - Page 1
Forum section: electronics / general

author: Bob Sava
author_rank: Regular Contributor
timestamp: September 21, 2020, 12:06:40 pm
content: Does anyone know what is the 60 pin connector name that this PowerEdge R620, R720, R720xd, R820 daughter card is using?example card (R1XFC):https://www.dell.com/en-us/shop/intel-ethernet-i350-qp-1gb-server-adapter-network-daughter-card-customer-installation/apd/430-4437/networking#techspecs_section
HP5526A Laser Interferometer from the 70's - Page 1
Forum section: electronics / general

author: iandmacp
author_rank: Newbie
timestamp: October 25, 2019, 11:38:44 am
content: Hello EveryoneI've restored back to working condition a HP5526A Laser Measurement System as seen in this video:So far it is just the basic system elements but we are hoping to use the system for calibrating surface plates which will require hundreds of measurements. These will be impractical to transcribe longhand and manually key into a computer so we are hoping to trap the data directly from the unit.On the rear of the unit are a number of interface ports and one of these was originally designed for a plotter and calculator as shown here:http://www.n4mw.com/hp5526/hp5526a.htmAs you can imagine this equipment is no longer around so we want to capture the 9x4 bit BCD (positive logic) outputs on one of the connectors at the back. These BCD digits mirror the nine nixie tubes at the front.As I don't want to burn out anything inside the unit I'm looking for feedback on the interface design shown in the pdf below. Basically the BCD output latch is driving the LED in the optocoupler and nothing else. The opto is driving the hex buffer and the buffer feeds the display LED and transciever which puts it onto an 8 bit bus. Several units will be required and I want to sequence them with software and an MCU to capture all nine 4 bit words.Any advice particularly regarding currents between the elements is greatly appreciated.Kind RegardsIan

author: guenthert
author_rank: Frequent Contributor
timestamp: October 29, 2019, 04:55:39 pm
content: While this is an (interesting) vintage device, I'd guess, you might fetch more relevant replies in the 'project' section. Good luck!

author: barijan
author_rank: Contributor
timestamp: September 13, 2020, 05:04:00 pm
content: I know this thread is a bit dated but here's suggestion.Why not using a Arduino Mega to capture the BCD signals, convert it properly by software and send it through USB to a modern computer.It has to be the Mega version, because it has much more I/O ports than regular Arduinos, and those will be needed to connect all BCD lines.I'm not an Arduino master at all but I'm sure it can be done.Correct me if I'm wrong, but I think Arduino can handle TTL levels easily and safely (considering it´s connected correctly) so, if you have no significant grounding problems between the equipment and the computer I think there's no need of optoisolators and buffers.I'm planning doing that in the furure for a old capacitance meter I acquired recently. It also has 4-bit BCD outputs, 4 digits for capacitance, 3 for dissipation factor and one for range. Total of 8 BCD digits to be handled altogether with some flag bits (signal, overflow, trigger and underange).All these signals are available at the 50-pin centronics connector on the back.And no, the 24-pin is not GPIB. I wish it was. Actually it is optoisolated outputs that may used to trigger actuators in a component sorting machine, based on the capacitance and dissipation factor thresholds set on the front pannel thumbwells.
Happy Birthday - Windows 95  - Page 1
Forum section: electronics / general

author: olkipukki
author_rank: Frequent Contributor
timestamp: August 25, 2020, 12:19:31 pm
content: What did they smoke?!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 25, 2020, 01:46:13 pm
content: Quote from: olkipukki on August 25, 2020, 12:19:31 pmDevelopers!

author: Circlotron
author_rank: Super Contributor
timestamp: August 25, 2020, 01:59:35 pm
content: "You make a grown man cry"...https://youtu.be/lAkuJXGldrM?t=16

author: HighVoltage
author_rank: Super Contributor
timestamp: August 25, 2020, 02:05:08 pm
content: I could never understand the hype around Win95 at the time.We switched from DOS to Windows NT4 about one year later, in 1996, I think and skipped Win95 completly.

author: Bud
author_rank: Super Contributor
timestamp: August 25, 2020, 06:42:00 pm
content: Just a rehearsal for the upcoming Monkey Dancehttps://youtu.be/7Ie7ypBNzFc

author: rrinker
author_rank: Super Contributor
timestamp: August 25, 2020, 07:06:44 pm
content: It was a massive change in UI from Windows 3.1. Lots of people were using 3.1 at the time, so it was a big upgrade.We got signed up for the beta program fro Windows 95, so we were messing around with it and trying different applications long before it was released. No downloading new builds in those days, they sent one on CD, using burned, not pressed, CDs - each one a different color. One had the distinctive scent of celery (don't ask why someone gave it a sniff test). Until a couple of moves ago, I had a stack of the old beta releases in a drawer. People turned them into clocks and things.It actually was pretty interesting, with each new build they would give a list of issues fixed and we would test that, as well as report any new issues found, they had a specific Beta Test site you could log in to to send bug reports and/or impressions or suggestions. I know we made a few. Our focus was mainly on development tools, I was mainly doing database application development with Foxpro in those days, and also third party networking (we were a Novell shop).After release, I got a 486 machine at home, but quickly switched to NT 4.0, although I did have it set to dual boot to Win95. I stuck to NT as much as possible though.

author: rrinker
author_rank: Super Contributor
timestamp: August 25, 2020, 07:09:35 pm
content: Quote from: olkipukki on August 25, 2020, 12:19:31 pmBill Gates - very uncomfortable, as many nerds are in party situations (myself included)Steve Ballmer - did enough coke prior that he didn't care.

author: Halcyon
author_rank: Unknown
timestamp: September 04, 2020, 11:14:10 pm
content: This is what happens when I ask a bunch of geeks to dance... I would look just as awkward.
MS and Commodore Easter Egg war  - Page 1
Forum section: electronics / general

author: Bud
author_rank: Super Contributor
timestamp: August 13, 2020, 01:52:46 am
content: A hilarious story about Easter Egg "war" between Microsoft and Commodore. Typing in some special few line of codes on Commodore 64 and running it reveal an interesting piece of historyFull video here explaining why that may have happened and how the code works:https://youtu.be/g8HHpmyFfw4

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: August 13, 2020, 06:53:06 am
content: heheI saw this vid when it first came out. You should understand that BG now can afford the best PR firm money can buy so you can expect pushback if you dare to satirize the all mighty.That said,
Driving TMS9918 clock - Page 1
Forum section: electronics / general

author: fabiodl
author_rank: Frequent Contributor
timestamp: July 01, 2020, 01:18:17 am
content: Thedatasheet of the tms9918page 3-11 reports in a footnote that when driven externally both inputs must be driven. Do they need to be driven by the same signal or by complementary signals?Do you know any existing hardware that drives them?I found thecolecovision schematicbut it seems that in this they are driving only xtal2

author: JXL
author_rank: Regular Contributor
timestamp: July 01, 2020, 03:36:28 am
content: Drive them with complementary signals. Use 74HC04 or similar.
16x TSM4256 replaced by 1x IS41C16256C or IS41C16257C - Page 1
Forum section: electronics / general

author: SoundLockEng
author_rank: Contributor
timestamp: May 21, 2020, 09:34:02 am
content: Hi all,Im looking for some advice as I am a bit out of my comfort zone in vintage computer design... or just computer design...So I am looking at replacing a PCB i have that addresses a 16bit bus into 16x TSM4256 chips simultaneously with either 8 or 9 bit addresses.I was wondering if it would be able to replace the 16 4256 chips with a single IS41C16256C or IS41C16257CI think it should work, however I am not sure about the refresh cycle and nuances that i have missed.I have attached a PDF of the original DMX96.2 card that I have reverse engineered and my take on the version with the ISS chip (DMX96SL) I believe addressing LCAS and UCAS at the same time with the same CAS signal is the correct thing to do...Any advice is much appreciated!All the bestChris

author: cruff
author_rank: Regular Contributor
timestamp: May 21, 2020, 12:04:49 pm
content: It looks like that should work, as long as the timing requirements are being met. If the original board didn't distinguish upper/lower bytes, then connecting both CAS pins to the same signal is correct.

author: SoundLockEng
author_rank: Contributor
timestamp: May 21, 2020, 07:26:34 pm
content: Hi cruff, Thanks for your reply, Im glad that im aiming in the right direction! I have laid out a board so will give it a try!fingers crossed!

author: SoundLockEng
author_rank: Contributor
timestamp: May 22, 2020, 09:08:41 am
content: I thought I would take this a step further.The IS41C16256C has OE which the original TSM4256 chips didn't. Because of this they included E17 and E18 which are SN74LS245N giving the card tri-state connection to the data bus.I guess using a combination of the signal used for the cards OE, the direction signal and spare logic gates I could derive a signal for the IS41C16256C's OE pin and remove E17 and E18.I would think that also E19 (SN74LS244N) could also be removed as in the original design it is uses as a buffer for the 16 ram chips hanging off the address bus but now there is just the one, which will appear no differently than the IS41C16256C on its own...

author: SoundLockEng
author_rank: Contributor
timestamp: May 22, 2020, 09:27:19 am
content: Here is my updated idea removing the extraneous IC's and using leftover logic gate to drive the OE for the ISS chip from the incoming card enable and card data direction.

author: cruff
author_rank: Regular Contributor
timestamp: May 22, 2020, 12:24:55 pm
content: The same optimizations had also occurred to me, so what you are proposing may be workable. As you say, the refresh cycles should be looked at to see if it will behave properly.

author: SoundLockEng
author_rank: Contributor
timestamp: July 06, 2020, 09:26:00 pm
content: So I just thought that I would update the thread to say that the boards work really well!!I made the version with the least number of components using the OE facility on the RAM chip rather than the tri-state chips that were a remenance of the original design.Thanks all!
Video: Deep Dive Looking For Green Tint on Inves Spectrum+ - Page 1
Forum section: electronics / general

author: llopis
author_rank: Contributor
timestamp: July 02, 2020, 02:28:03 pm
content: Here's my latest video: A DEEP dive into the color-generation circuitry of the Inves Spectrum+ (a clone of the ZX Spectrum+) chasing down a green tint on the screen. This one is particularly technical, so hopefully a lot of people in this forum will enjoy it.If you want some background on this and the machine itself, here's my previous video on it:

author: Bud
author_rank: Super Contributor
timestamp: July 02, 2020, 06:55:07 pm
content: I have a problem understanding why the modulator would have such a profound effect on the composite color encoding. Possibly there could be a detuned resonant circuit inside that threw the PAL burst out of wack so the decoder inside the TV did not sync with the burst phase properly. Are you going to investigate further?Edit: One suggestion would be to connect the troublesome tinted composite signal to the oscilloscope and check the color burst amplitude, shape and maybe position against the PAL standard. The peak to peak amplitude should be 300mV or so.

author: llopis
author_rank: Contributor
timestamp: July 02, 2020, 07:43:48 pm
content: Quote from: Bud on July 02, 2020, 06:55:07 pmI actually don't know. I'm not familiar at all about the inner workings of RF modulators, so maybe someone else can chime in. I believe someone in the YouTube comments said something along the lines of what you're suggesting. I'm not going to dig any deeper in the RF modulator for now. I already have a list of videos I want to make way longer than I can possibly make in a year :-/I didn't show the color burst in the video, but it seemed totally normal from what I'm used to seeing. The color burst had to be fine because it's generated in the MC1377P and I tried different ICs there, all with the same result. So yeah, the fault definitely had to be in the RF modulator.
The story of Tetris - Page 1
Forum section: electronics / general

author: Bud
author_rank: Super Contributor
timestamp: June 18, 2020, 10:35:06 pm
content: This is an almost detective story about the creation and fight for the Tetris game. It involved big caliber players, was lobbied at the government level, and caused a serious fight between the Japanese gaming behemoth companies. Also teaches you a lesson to pay attention to details in contractshttps://youtu.be/_fQtxKmgJC8

author: andy3055
author_rank: Super Contributor
timestamp: June 19, 2020, 02:33:39 am
content: Great! The only game I ever enjoyed
does anybody know this calculator model name? - Page 1
Forum section: electronics / general

author: aqarwaen
author_rank: Regular Contributor
timestamp: May 20, 2020, 12:07:38 pm
content: i scored this very small calculator from used item shop.all i can findis erikshjälpen,but no ohter info.any clue what chipset this calculator may use?

author: edpalmer42
author_rank: Super Contributor
timestamp: May 20, 2020, 07:10:04 pm
content: I have two similar calculators that were giveaways from companies. If you peel off the price tag, you might find a company name. One of mine is labelled Mitel. All the package says is 'Made in Hong Kong'. The other is from Northern Telecom. The model might be 'Grand Prix'. It was imported by Lidco in Markham, Ont. Mine are both ancient - maybe 20 - 30 years old.No idea what chipset was used. The thing is so thin that it must be a COB (chip on board) construction so it would be covered with an epoxy blob. For anyone reading this, these things are the size of a credit card and about 2.5 mm thick.Why do you want to know the chipset?

author: MLXXXp
author_rank: Frequent Contributor
timestamp: May 21, 2020, 01:56:27 pm
content: Quote from: aqarwaen on May 20, 2020, 12:07:38 pmCalculator forensics may give you a clue.http://www.rskey.org/~mwsebastian/miscprj/forensics.htmEdit: Oops! Sorry, without trig functions, the above link may not be helpful.

author: tunk
author_rank: Super Contributor
timestamp: May 21, 2020, 02:08:38 pm
content: Most likely it's from the second hand shop of erikshjälpenand "kr 49" is the price in SEK (currently about 5us$):https://translate.google.com/translate?hl=en&sl=sv&u=https://secondhand.se/om-erikshjalpen&prev=search

author: chriva
author_rank: Regular Contributor
timestamp: May 21, 2020, 02:54:14 pm
content: Indeed. Erikshjälpen is an organisation aiming to help children in need. I tend to pay a little extra for stuff when I buy from them. Good people
Commodore 64 chip porn - Page 1
Forum section: electronics / general

author: Bud
author_rank: Super Contributor
timestamp: May 12, 2020, 03:32:40 am
content: Someone went berserk reverse engineering the C64 chips and PCBs with I guess a microscope and X-rayhttp://oms.wmhost.com/misc/Just a few stunning images from the collection:http://oms.wmhost.com/misc/MOS_6569_R1.jpghttp://oms.wmhost.com/misc/MOS_8500_CPU.jpghttp://oms.wmhost.com/misc/C64C_xray.jpg

author: granzeier
author_rank: Regular Contributor
timestamp: May 12, 2020, 10:22:54 am
content: Very nice, thanks.
Macintosh LC II not being able to see two hard drives at the same time - Page 1
Forum section: electronics / general

author: gkmaia
author_rank: Frequent Contributor
timestamp: August 01, 2020, 07:51:06 am
content: I got an LCII with a hard drive inside.As I wanted a second hard drive I decided to make an adaptor to connect my other SCSI drive to it's rear SCSI port.If I start with the external HD connected it boots from the external Hd and the internal is not visible.If I start with the internal HD and later connect the external HD the external does not mount.Anything I should do such as setting the external as slave? Or come pinout on my adapter that I am missing?

author: tunk
author_rank: Super Contributor
timestamp: August 01, 2020, 09:45:16 am
content: Maybe they have the same SCSI ID?https://en.wikipedia.org/wiki/SCSI#Device_identification

author: gkmaia
author_rank: Frequent Contributor
timestamp: August 01, 2020, 10:14:11 am
content: that makes sense, thanks!they both mount at bus 0. I will see if I find a jumper to change their scsi id.
Microsoft Open-Sources "GWBasic" (1983 version for IBM-PC) - Page 1
Forum section: electronics / general

author: westfw
author_rank: Super Contributor
timestamp: May 25, 2020, 09:11:52 pm
content: Microsoft has open-sourced the 1983 version of GWBASIC:https://github.com/microsoft/GW-BASICIt's some pretty nicely commented (IMO) 8086 assembler. (Intel "strongly typed" assembler, which I always found a bit weird, but it was standard.)

author: Syntax Error
author_rank: Frequent Contributor
timestamp: May 25, 2020, 09:22:27 pm
content: I can say without any fear of contradiction, that's the most well commented code that I haveeverseen on Github. Thelatest commitis 38 years ago. That means this repo is older than Mark Zuckerberg!

author: chriva
author_rank: Regular Contributor
timestamp: May 25, 2020, 09:44:09 pm
content: I noticed the timestamp too. You just know a nerd somewhere giggled when that tweak was made

author: ebclr
author_rank: Super Contributor
timestamp: May 25, 2020, 10:48:29 pm
content: Is Bill Gates involved on this?

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 25, 2020, 11:12:48 pm
content: As can be seen in the source code:Quote
Does anyone remember the Terran T40? - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: April 20, 2020, 11:59:58 am
content: Does anyone remember an Australian designed (inc BIOS!) IBM PC clone back in maybe the early to mid 90's?IIRC it was called the Terran T40, but I cannot find a single reference to it except for this:http://minuszerodegrees.net/misc/Irwin%20tape%20drives.pdf#page=4

author: EEVblog
author_rank: Unknown
timestamp: April 20, 2020, 01:34:06 pm
content: Someone on twitter found some links:https://www.americanradiohistory.com/hd2/IDX-AUSTRALIA/IDX/Archive-Electronics-Australia-IDX/IDX/90s/EA-1990-01-OCR-Page-0138.pdfhttps://www.newspapers.com/newspage/120568579/Somehow involved with Microbee, and then they got sued and went out of business in 1997.
System General SGUP-85 Universal Programmer software - Page 1
Forum section: electronics / general

author: jord4231
author_rank: Regular Contributor
timestamp: April 19, 2020, 06:17:22 am
content: I've got this old SGUP - 85 universal programmer.I've searched the web high and low. I found a forum that long dead unfortunately. I've even contacted the manufacture who no longer have the software.Just by any chance does anyone have a copy. It would be good to fire this old thing up again.Currently stand alone you can do a few things but the software would be nice.
3Dfx Voodoo 2 8Mb to 12Mb Upgrade - Page 1
Forum section: electronics / general

author: dexters_lab
author_rank: Unknown
timestamp: April 11, 2020, 08:19:30 am
content: So i picked up two matching 3Dfx voodoo 2 cards for a project pc i am building, both are Creative Labs CT6670, only one of them is the cut down 8Mb version so i figured it's only a soldering job to upgrade it right?It requires soldering on 8 512Kb EDO SOJ DRAMs, all the other decoupling / passives seem to be there. I have sourced some (hopefully not blacktopped!) NOS EM614163A-25 devices from Utsource which should arrive next week.Now I have soldered SOJ with an iron before, but some of the the drams are pretty close together to get the iron in, unless hot-air might be better?Would be interested to hear if anyone else has done this here?

author: SeanB
author_rank: Super Contributor
timestamp: April 11, 2020, 08:57:07 am
content: I would say preheat the board, then hot air, as those thermal planes under the memories are pretty huge, so even soldering it will need a lot of heat.

author: dexters_lab
author_rank: Unknown
timestamp: April 12, 2020, 11:34:38 am
content: Quote from: SeanB on April 11, 2020, 08:57:07 amthanks, yea i know what your saying, i just feel more comfortable using an iron!

author: james_s
author_rank: Super Contributor
timestamp: April 12, 2020, 10:50:42 pm
content: Careful not to heat it up so much that parts drop off the other side of the board.Those look like they'd be pretty trivial to solder with an iron, might need a narrow wedge tip though. Use some flux and make sure you inspect very closely for bridges and clean the flux off.

author: dexters_lab
author_rank: Unknown
timestamp: April 18, 2020, 06:45:37 am
content: Mission completeUsed an iron, video here details it all...
Hardware for Solaris 2.5-2.6 (pre-Solaris 7 era) - Page 1
Forum section: electronics / general

author: olkipukki
author_rank: Frequent Contributor
timestamp: April 17, 2020, 07:07:57 pm
content: I would like to try some software that requires Solaris 2.5-2.6 and build for UltraSPARC CPUSun Ultra 5 looks tick all boxes, but might there something better and not much bigger, the space is really issue.Any suggestions?
Trying to find Adtron SDDS-03A Firmware - Page 1
Forum section: electronics / general

author: baakre
author_rank: Newbie
timestamp: April 16, 2020, 09:01:33 pm
content: Hi all,I'm trying to locate a copy of the firmware for an Adtron SDDS-03A SCSI to PCMCIA card adapter. I've got an Adtron SDDS-04A that appears to be physically identical to the SDDS-03, so I'm thinking the difference may be down in the firmware. If anyone has one of these or knowledge of what might be different, I'd love to hear about it. The Adtron SDDS-04A appears as a SCSI tape drive whereas the SDDS-03A appears as a removable SCSI disk.Thanks!
The Machine That Changed The World - Page 1
Forum section: electronics / general

author: bobcat2000
author_rank: Regular Contributor
timestamp: April 14, 2020, 04:54:35 pm
content: They had this documentary on TV long time ago. I really enjoyed watching this documentary. Just want to share with you guys if you are into computing.https://waxy.org/2008/06/the_machine_that_changed_the_world/

author: bobcat2000
author_rank: Regular Contributor
timestamp: April 15, 2020, 06:20:48 am
content: This was one big hard disk in the back.