EEVblog #746 - Sharp X68000 Retro Computer Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: May 20, 2015, 12:04:36 pm
content: electronics.de/datenblaetter/Schaltkreise/MB81256.pdfhttp://dev-docs.atariforge.org/files/MC68901.pdfhttp://pdf1.alldatasheet.com/datasheet-pdf/view/870/MITSUBISHI/M51387P.htmlhttp://www.datasheetspdf.com/PDF/HD63450/774601/1

author: EEVblog
author_rank: Unknown
timestamp: May 20, 2015, 12:44:04 pm
content: Quote from: wilfred on May 20, 2015, 12:29:11 pmI'd fix it if it was a grammar mistake and not a spelling mistake

author: coppice
author_rank: Super Contributor
timestamp: May 20, 2015, 01:01:30 pm
content: Quote from: EEVblog on May 20, 2015, 12:44:04 pmI don't think I can really respect the sought of person who can't be bothered to polish their work.

author: Fungus
author_rank: Super Contributor
timestamp: May 20, 2015, 01:20:32 pm
content: Base has5screws....

author: Fungus
author_rank: Super Contributor
timestamp: May 20, 2015, 02:16:49 pm
content: Don't want to derail the thread but ... it reminded me a bit of my old twin-tower SGI VGX (a machine truly worthy of a teardown).The main tower on the left had a door which opened to show a PCB holder, like this:Pull the white levers at top/bottom to slide the PCBs out.The PCBs were huge(big enough to need strengthening bars bolted to them to stop them bending under their own weight) andcrammedwith those vertically mounted SIP RAM packages like in the X68000 (that's what made me think of this).There's high-res photos of some of the PCBs here:http://www.sgistuff.net/hardware/systems/powerseries.html(look for "VGX graphics" near the bottom - just the graphics system was spread across four of those PCBs! (orfiveif you were rich enough to afford two raster managers to get double the pixel fill rate!)The smaller tower on the right had the power supply at the bottom and you could build it up using stackable SCSI units (containing disks, tape drives, etc). You could stack them pretty high if you had enough money!More photos here:http://www.flickr.com/photos/31231773@N02/sets/72157630939129520/Those things wereHEAVYandnoisy as hell(multiple 16cm fans at high speed). SGI made a special sling that you could slip underneath with handles so that two people could lift one (usually onto a wooden pallet for a fork-lift to take them to the truck). Yes, I've carried one up some stairs.Ah, those were the days ... before a $250 PCI graphics card replaced the entire thing.

author: cyr
author_rank: Frequent Contributor
timestamp: May 20, 2015, 03:23:26 pm
content: Are those three F-series chips on the video board really socketed? Looked a bit like ferrite to me, EMI fix?

author: bktemp
author_rank: Super Contributor
timestamp: May 20, 2015, 03:25:27 pm
content: Those memory ICs Dave was unable to find any info used in the video setion are dual port DRAMs (also known as VRAMs):http://pdf.datasheetcatalog.com/datasheets/2300/500355_DS.pdfBasically DRAMs with an additional SRAM FIFO port for serial IO and internal parallel connection to the DRAM. This allows fast serial input or output of data while the CPU can access the DRAM at the same time.Using a similar VRAM IC and a microcontroller I built my first DSO and logic analyser many years ago running at 32MS/s. Because all the fast adress counting logic is built into the memory it was very easy to sample all kinds of signals and store them into the large DRAM.

author: rsjsouza
author_rank: Super Contributor
timestamp: May 20, 2015, 06:35:40 pm
content: Good video; as someone on the Comments section said, I agree this machine deserves a Part II teardown of the missing components.

author: boffin
author_rank: Unknown
timestamp: May 20, 2015, 06:46:00 pm
content: SASI (Shugart Associates System Interface) after the Shugart Hard Drive company - later renamed to SeagateIt was the forerunner of SCSI (which as a standard they didn't want to name after a company) and for all intents and purposes they're the same thing.

author: BUkitoo
author_rank: Contributor
timestamp: May 20, 2015, 06:52:22 pm
content: Could the cross/arrows simbol at the corner mean the coordinate reference of the board?The simbol is near a fiducial mark.

author: caius
author_rank: Regular Contributor
timestamp: May 20, 2015, 07:24:42 pm
content: I have three X68000 machines and I can confirm they are from another planet compared to other personal computer of the same era.Just to say one, CAPCOM used this platform to develop some of they arcade games.Its hardware design is totally different from a normal pc starting from the floppy drive which have a soft-eject mechanism and some proprietary signals on the Shugart bus.If you need further indo about this wonderful machine, I recommend you all to visit this forum:http://nfggames.com/forum2/index.php#c2

author: cbmuser
author_rank: Newbie
timestamp: May 20, 2015, 07:26:25 pm
content: I'm sorry, Dave, but the X68000 isn't superior to the Amiga. In fact, it doesn't even compare the first versions of the Amiga.The Amiga had a preemptive 32-bit multitasking operating system, DMA audio and a high-performance custom chipset for graphics and DMA.Windows didn't have a 32-bit preemptive kernel before 1995 and MacOS users even had to wait until 2001 (MacOS X).Just a comparision, here are some typical X68000 games:And here is a demo that already runs on an original A500:If you take later Amigas like the A1200, it's even more apparent how superior the Amiga's design was:No other 68k machine compares to the Amiga when it comes to graphics and sound, except maybe the highend stuff from SGI or NeXT. But those usually cost a couple grands and are therefore out of the comparision.Adrian

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: May 20, 2015, 07:41:10 pm
content: Quote from: BUkitoo on May 20, 2015, 06:52:22 pmTo me it looks more like a polarity indicator for the polarity sensitive two-legged components.

author: caius
author_rank: Regular Contributor
timestamp: May 20, 2015, 07:54:27 pm
content: Quote from: cbmuser on May 20, 2015, 07:26:25 pmPardon but how can you say this?Do you have an X68000?Try to play perfect arcade ports like Final Fight and many other and you will change you opinion!Maybe Amiga hardware was not fully exploited but the software is the touchstone between two machines and the X68000 is far better than Amiga under this point of view.

author: caius
author_rank: Regular Contributor
timestamp: May 20, 2015, 08:16:21 pm
content: Dave, you can find schematics here:http://nfggames.com/x68000/Schematics/Outside%20X68000%20-%20Schematics/CZ-600CE%20(Core).tifhttp://nfggames.com/x68000/Schematics/Outside%20X68000%20-%20Schematics/CZ-600CE%20(Peripherals).tifhttp://nfggames.com/x68000/Schematics/Outside%20X68000%20-%20Schematics/CZ-600CE%20(Video%201).tifhttp://nfggames.com/x68000/Schematics/Outside%20X68000%20-%20Schematics/CZ-600CE%20(Video%202).tif

author: rob77
author_rank: Super Contributor
timestamp: May 20, 2015, 08:29:04 pm
content: Quote from: cbmuser on May 20, 2015, 07:26:25 pmactually you should compare apples with apples - you comparing a x68000 game with amiga demos...the demos are using up every available resource to show off the maximum the hardware can do - not leaving a single CPU cycle available for user interaction.... while the games must react quickly to user input and therefore you can't expect the same sound and graphics as in demos...

author: Sigmoid
author_rank: Frequent Contributor
timestamp: May 20, 2015, 08:30:14 pm
content: Quote from: cbmuser on May 20, 2015, 07:26:25 pmAnd how does that have anything to do with the computer itself?!Besides, most (all?) Amiga games were booted on the bare metal, which means no OS, which means no kernel to speak of.Quote from: cbmuser on May 20, 2015, 07:26:25 pmA DEMO?! Really? Come on, you can't be serious! Demos are programming masterpieces that enhusiasts build to show off their absolute mastery of the system and their coding prowess. A demo does not show off the capabilities of a system. It shows off the capabilities of its creator.To drive home the point... This here is a C64 DEMO:..while this is a typical c64 game demonstrative of the hardware's capabilities in the hands of a good programmer:As for which system is more powerful, you should read the specs. And the x68000 blows the Amiga far out of the water when it comes to specs, in sound channels, in number of sprites, in screen resolution, in processor speed, in any actual metric possible.It's okay to be an Amiga fanboy, but don't be crazy.

author: hyperneogeo
author_rank: Newbie
timestamp: May 20, 2015, 09:35:37 pm
content: I'm glad Dave got to this and hopefully I'll be able to send more interesting Japanese computer examples. There were a ton of interesting computing devices that were only limited to Japanese markets.The X68000 had interesting things like Midi cards, Video Card upgrades (nothing 3D mind you, pure 2d), processor upgrades (to 030 / 060 processors) and other cool upgrades. The other interesting thing is the x68000 had a huge huge huge indie game market which led to a lot of interesting games. Recently a few people released a few laser disc game ports on the x68000. Sure you need a very beefy/expensive processor upgrade to do it, but it's there.Indie Games:Retail:The x68000 wasn't really made to do 3D, but people sure did try:Tons more, but just a few examples. The x68000 was a really nice shooting game system as you can probably tell.

author: senso
author_rank: Frequent Contributor
timestamp: May 20, 2015, 10:57:50 pm
content: So, can it run MetalSlug?

author: EEVblog
author_rank: Unknown
timestamp: May 20, 2015, 11:42:47 pm
content: Quote from: cyr on May 20, 2015, 03:23:26 pmAh, nice spotting, indeed it is a ferrite plate.

author: pickle9000
author_rank: Super Contributor
timestamp: May 21, 2015, 01:16:24 am
content: So will there be a powersupply teardown followup?

author: hyperneogeo
author_rank: Newbie
timestamp: May 21, 2015, 02:43:07 am
content: It's interesting to note that many people take the power supply out and replace it with a pico power supply (and rewire it a little) as the original power supply has some rather weird problems.

author: Mysion
author_rank: Regular Contributor
timestamp: May 21, 2015, 04:51:31 am
content: That was a rather fascinating tear down. It's not often that you see the insides of a non European/US computer. I'm surprised how well the style held up. It doesn't look like it's 20+ years old. I was assuming early 2000's.It'd be nice to see a part two of this. What would really be awesome is an analysis on why the power supply is so bad.Awesome vid!

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 05:19:47 am
content: Quote from: rob77 on May 20, 2015, 08:29:04 pmCame here to say that. Comparing real games with "demos" is apples to oranges.The Amiga was amazing at demos but real Amiga games never looked like that (or if they did, they were terrible games).Edit:(after a quick google search)Oh, glub... it'sactually on there...!Here's a demo I wrote on the Atari ST in the 1980s:I wrote it just to annoy Amiga fanboys at the local computer shop (skip to 2:05 for the good bit).It doesn't show well in that video but it was a totally smooth 60Hz parallax scroll over most of the screen. Useless for a game because it used all the RAM and only had enough CPU left for a single sprite, but not a problem for a demo.That thing traveled pretty much all over the world on floppy disks from a single copy I left in a computer shop. Quite amazing. I remember getting letters from faraway countries for years afterwards asking why I didn't make it into a full game (actual letters, written onpaper...)(And yes, that's how long Amiga Fanboys have been annoying people...)

author: bitwelder
author_rank: Super Contributor
timestamp: May 21, 2015, 05:52:26 am
content: The Cynthia Jr. chip seems to be just some kind of buffer(From the Video 2 schematics posted earlier)

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 05:55:34 am
content: Quote from: Mysion on May 21, 2015, 04:51:31 amYes, nice design. I'd totally have something like that on my desktop today if they made PCs like that.Carrying handle is perfect for LAN parties (or whatever they call them these days)

author: pickle9000
author_rank: Super Contributor
timestamp: May 21, 2015, 05:59:05 am
content: I've been looking at some of the games for the Sharp, you can certainly see why it was sought after. The games are really arcade quality, both the sounds and graphics are bang on.It's so surprising to such an amazing product, I had no clue it even existed until today. Many thanks to the person that sent it in.

author: hyperneogeo
author_rank: Newbie
timestamp: May 21, 2015, 05:59:59 am
content: Quote from: senso on May 20, 2015, 10:57:50 pmMetal Slug was made wayyyy after the x68000. (Think PSX era).

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 06:06:43 am
content: Quote from: pickle9000 on May 21, 2015, 05:59:05 amYep.Quote from: pickle9000 on May 21, 2015, 05:59:05 amNor me, although it's not really surprising; Japan had lots of weird home computers in the 80s that nobody in the west ever heard of.Quote from: pickle9000 on May 21, 2015, 05:59:05 amIt's been a trip down memory lane.A bit of a cop-out for the power supply though, what's with the "out of time" business? There was still half an hour of video left...

author: Stonent
author_rank: Super Contributor
timestamp: May 21, 2015, 07:48:29 am
content: True arcade perfect requires a 16 to 20 MHz 68K processor, Zilog Z80 (as a sound controller) and the Yamaha FM Synth + DAC.That will cover most capcom and Sega up to System 16, possibly System 18. I think System 24 may have used dual 68K processors.Though not a computer the Neo Geo was probably was the best 68K hardware system for doing this.The Sega Genesis (Megadrive outside of the US) had a slower 68K processor but had the Z80 and yamaha chipset. It suffered by having a lower color bit depth video and did not have a dedicated DAC for non-FM synth audio.The Super Nintendo's CPU was slower still and had a lower screen resolution than the Genesis, but had more RAM and better audio DAC so it could use wave table synthesis. It also had a palette of 256 colors out of 32k vs 64 colors out of 512.The Amiga had a faster 68k processor but no yamaha synth. The dedicated graphics hardware made it easy to offer the video experience needed for arcade graphics. The lack of the yamaha synth meant that it would have to use sampled audio.

author: German_EE
author_rank: Super Contributor
timestamp: May 21, 2015, 08:27:24 am
content: Am I the only one who thinks that IBM were INSANE when they chose the 8086 for their PC rather than the 68000? I remember seeing single board 68000 systems in the workshop when I was repairing PCs and the Motorola based systems were an order of magnitude faster than the PC-XT. Also, the memory map of the 8088/8086/80286 is a mess

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 08:32:53 am
content: Quote from: Stonent on May 21, 2015, 07:48:29 amThe Amiga could scroll the screen all over the place using hardware/'copper' but it had no sprites worth speaking of. Sprites is where the X68000 would totally destroy an Amiga.Yes, you could turn on more bitplanes as an overlay and use the blitter instead but that reduced you to 8 colors on screen and totally blocked the CPU in the visible screen area due to lack of RAM bandwidth (the CPU only ran in the border areas and vertical flyback, just like a ZX81!)The X68000 has those high-speed RAM chips for a reason.Quote from: Stonent on May 21, 2015, 07:48:29 am...and those same sound samples would eat up all the RAM in no time, leaving nothing for graphics.Stuff like this is what made the Amiga really terrible for games (but excellent fordemos!).

author: miguelvp
author_rank: Super Contributor
timestamp: May 21, 2015, 08:33:44 am
content: They were competing with CP/M 80 (Z80/8080) based CPUs, so it made a lot of sense to base it on the 8088 (not 8086).The OS was going to be CP/M 86 but they struck a "deal" with Microsoft, and used off the shelve components, and the rest is history.

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 08:40:30 am
content: Quote from: German_EE on May 21, 2015, 08:27:24 amIBM deliberately chose something a bit crap because they didn't want PCs to eat into their 'real' computer business. It was also compatible with CP/M, a big plus in their target market.In the long term Intel turned out to be a far better choice. By the time of the 386 it was leaving Motorola behind, the 486 left it for dead.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: May 21, 2015, 09:03:13 am
content: It's lore and I'll try to find some proper evidence but my recollection is that IBM never really expected their PC to take off. That's part of the reason they didn't go to the expense of developing their own OS or purchasing the exclusive rights to DOS from Microsoft. Furthermore, the original PC was based off some 8085 running word processor IBM already had, and dropping in an 8088 made for a simple "16 bit" modern PC on the cheap.The 68000 needed a real 16 bit external bus, which added a lot of expense. For example it's hard to route 16 bits on a two layer board, and DRAM was typically by 1 bit so you needed 16 RAM chips minimum. The 68008 didn't have a BUI like the 8088 so they suffered a terrible performance penalty. Also the 8086 instruction set was translatable from 8080 code so theoretically existing CP/M software was easily run, or at the very least easily converted. This partly explains the messed up memory system too, and I'll point out that this has been the historical success of the 8086 platform: that compatibility is more valuable than orthogonality.

author: dexters_lab
author_rank: Unknown
timestamp: May 21, 2015, 09:18:18 am
content: i seem to recall some legacy reasoning with the original XT and the 8088, the 68k was a much newer processor design... the Atari ST and Commodore Amiga were both fresh new designs at the time and were made for a very different market spacenice to see the insides of this X68000 machine, some very serious design there, some big dedicated hardware that would make the ST and Amigas custom silicon go week at the knees!But then $1500 price tag, in Japan... wow, if that was sold to the US or EU markets it would have been $2000+ by the time i was exported and on the shelves. Nobody would have bought it!it's physical monolithic black box design reminds me a bit of the NeXT, which interestingly was also 68k

author: bktemp
author_rank: Super Contributor
timestamp: May 21, 2015, 09:28:17 am
content: As a comment for mentioning the amount of 74 series logic used in that computer, have a look at this 386 mainboard from IBM:It is a mix of ASICs (unter the metal cans), PLDs (PALs, MMI 72x7486) and a lot of 74 series logic. They did even make their own memory modules and ICs instead of using the standard SIMMs.

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 10:26:37 am
content: Quote from: bktemp on May 21, 2015, 09:28:17 amYep, those first boards were monstrous. Even so all floppy disks, serial ports, parallel ports, hard drive controllers, etc. were on separate ISA cards.I remember being amazed by my first "all in one" ISA card that had hard disk, floppy, serialandparallel on the same expansion card.Kids, today..

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 10:35:51 am
content: Quote from: Paul Moir on May 21, 2015, 09:03:13 amIt's a classic tale: The top bosses were against it, a small team of heroic engineers hacked the first one together in record time. ...the rest is history.https://www-03.ibm.com/ibm/history/exhibits/pc25/pc25_birth.htmlQuote from: Paul Moir on May 21, 2015, 09:03:13 amThe 8-bit bus of the 8088 was a big point in its favor.

author: RupertGo
author_rank: Regular Contributor
timestamp: May 21, 2015, 11:59:23 am
content: There were two problems with the 68K for the IBM PC - Motorola couldn't deliver parts, and it had disbanded its design team before it realised it needed peripheral chips (I seem to remember the thinking was that the 6800 stuff could do the job, but I wouldn't swear to it.)IBM wanted something quick and dirty, and Intel had all the bits ready. If you look at the original PC, it's basically Intel reference designs glued together. As someone who had to write a lot of low-level 8086 code back then, I still bear the scars. I also did 68k on the Amiga, which was cosmically nicer, but that was never where the money was. (The 386, however, was enormously better than the 8086/286, and writing native 386 code felt like doing grown-up programming for the first time...)The Sharp is an amazing machine, it's most of an arcade box with a general purpose computer in there as well. The design effort must have been really something. But there can't be many post-Lisa 68K designs with 5.25" floppies.

author: hikariuk
author_rank: Unknown
timestamp: May 21, 2015, 03:54:14 pm
content: Quote from: Fungus on May 21, 2015, 05:19:47 amWas that using the BLiTTER on the later STs or just running on the M68k?

author: hikariuk
author_rank: Unknown
timestamp: May 21, 2015, 03:55:59 pm
content: I still have my M68k assembly language programming guide book.

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 05:40:45 pm
content: Quote from: hikariuk on May 21, 2015, 03:54:14 pmJust on the 68000.It's been 30-odd years since I wrote that, but... IIRC the trick is to store 16 pre-shifted versions of the graphics in memory so no data shifting is needed during screen update (you pay the price in RAM). It also has 4 colors so you only copy half the usual amount of data (normally 16 colors=4 bitplanes, the demo uses 4 colors=2 bitplanes).

author: Sigmoid
author_rank: Frequent Contributor
timestamp: May 21, 2015, 06:49:19 pm
content: Quote from: RupertGo on May 21, 2015, 11:59:23 amActually, while the PC may have been a sorry piece of hardware when viewed through the eyes of the enthusiast, looking at it from a management and engineering perspective, it's a masterpiece of unprecedented beauty. They built something without building anything.Nowadays it's corporate fad to brandish bon mots like "maximize the amount of work not done". Well, they certainly did that. They also brought open architecture into a field dominated by vastly incompatible proprietary solutions.Well done, IBM.

author: hikariuk
author_rank: Unknown
timestamp: May 21, 2015, 09:18:43 pm
content: Quote from: Sigmoid on May 21, 2015, 06:49:19 pmThe 8086's rather bizarre register conventions are also an artefact of some crafty engineering (like BX being the only register you can use for memory access). It made porting from the 8080 based CP/M machines automatable.

author: Kevman
author_rank: Regular Contributor
timestamp: May 22, 2015, 12:47:57 am
content: Man, I've been wanting an X68000 ever since I saw the Game Sack episode on it a few weeks ago. I was shocked to see Dave with one, what a coincidence! Also stupidly jealous.It seems to have some serious advantages over the Amiga (though you can't beat MODs). Remember, though that its 2 years newer and 2 years is a loonnngg time in the computer world!Interesting to see the Demoscene come up again here.Has anyone been to any Demoparties lately? I do the livestreaming for the American ones.

author: pickle9000
author_rank: Super Contributor
timestamp: May 22, 2015, 12:59:39 am
content: So I guess the next question is will Dave try and bring the thing back to life? Could have a very high view count seeing as it's rare. Then perhaps auction it off or use it as a contest prize.

author: TiN
author_rank: Super Contributor
timestamp: May 22, 2015, 12:20:00 pm
content: Love those chip names and silk screen on bottom for debug aid

author: fsanches
author_rank: Newbie
timestamp: May 23, 2015, 05:08:56 pm
content: MAME has an X68000 driver (in the MESS portion of the project), but I am not sure how well does it emulate this system.MAME developers would definitely benefit from it in order to improve the emulation. I am not sure, Dave, what will you do with this unit after you're finished recording the teardown videos. If it is going to simply stay sitting in a storage room, then perhaps you could consider donating this unit to one of the MAME/MESS developers. Perhaps R.Belmont would be the ideal choice. See this thread where he mentions his work on trying to emulate the X68000 system:http://forums.bannister.org/ubbthreads.php?ubb=showflat&Number=28935It is worth mentioning here, as well, that MAME/MESS source code is a very rich source of technical documentation on these kinds of devices, since the project's main stated goal is to document the history of arcade game hardware and old digital equipment in general as well.The X68000 driver source-code can be seen here:https://github.com/mamedev/mame/blob/master/src/mess/drivers/x68k.cIt is filled with comments covering the technical architechture of this system and I would call your attention specifically to this portion which ties together the several parts of the system emulation:https://github.com/mamedev/mame/blob/master/src/mess/drivers/x68k.c#L1637happy hacking,Felipe SanchesPS: I am a code contributor to MAME and MESS but I am not yet a member of the core development team.

author: RupertGo
author_rank: Regular Contributor
timestamp: May 23, 2015, 08:50:22 pm
content: The PC may have been a thing of beauty from some perspectives, but never from mine. We had to build hardware and write software for it, and got bitten on the bum by many of the shortcuts in the specification. The ISA bus, for example, which assumes that worst-case (within spec) timing will never happen, and has a whole bunch of other stuff just undefined. Including, if I remember correctly, the mechanical spec for the mounting bracket for expansion cards. And as for the undershoot... early ASICs did not like a bus-worth of that dumped to substrate by the clamp diodes. And that's before you start to battle with what's actually implemented by the cloners.And the BX register wasn't the only one that could access memory. SI and DI did that too. What was it - Accumulator, Base, Count and Data for AX, BX, CX and DX? No, those weren't problems; a Z80 guy like myself liked the extra room and non-orthogonal just gave one's code a lovely baroque feel.The segment registers, though, one did not like. One did not like them really rather a lot, although it was possible, once you'd been through the pain of learning to think that way, to commit some extraordinarily evil tricks with data structures that those airy-fairy C programmers found quite beyond the pale. And no snooty MMU to tell you off.We've come a long way in thirty-odd years.

author: vlad777
author_rank: Frequent Contributor
timestamp: May 24, 2015, 12:12:25 pm
content: Quote from: bktemp on May 21, 2015, 09:28:17 amWhat is that bus ? It's not ISA. It 's not VLB. Can't be PCI. Some of connectors look like 64 bit PCI?

author: bktemp
author_rank: Super Contributor
timestamp: May 24, 2015, 01:00:05 pm
content: Quote from: vlad777 on May 24, 2015, 12:12:25 pmI think it is MCA:https://en.wikipedia.org/wiki/Micro_Channel_architecture

author: Tothwolf
author_rank: Regular Contributor
timestamp: May 25, 2015, 10:23:58 am
content: Quote from: bktemp on May 24, 2015, 01:00:05 pmIt has been decades since I worked on one, but I'm pretty sure that is the main board from a 386 based PS/2 Model 80. These IBM PS/2 full tower style boards were huge, and even with an integrated parallel port, a serial port, and on-board VGA (up to 640x480, 16 colors), you really did need the slots. At a bare minimum I usually used at least two boards, an ESDI and/or SCSI controller and a network board (Western Digital or 3Com 10Base-2). If you wanted higher resolution VGA (1024x768, 16 colors; 256 colors if you added the additional 512K daughter board), the 8514/A adapter would take yet another slot. The same goes if you needed more than one serial port (we often did), and a dual serial port card would eat another slot. Even with all the MCA slots in these tower style PS/2 systems, there never seemed to be enough.

author: Stonent
author_rank: Super Contributor
timestamp: May 26, 2015, 01:41:48 am
content: The main reason IBM went with the 8088 was that it was peripherally compatible with Intel parts they had from the 8085 based IBM Datamaster and the 68000 had just hit the market in 1980. Motorola did not have the peripheral chips available in the kind quantities that IBM needed. They definitely wanted a CPU that could deal with more than 64k out of the box but didn't really see the PC as being worth a lot of invesyment. At one time they had even considered completely outsourcing the design to a third party but in the end decided just to outsource the OS.

author: RupertGo
author_rank: Regular Contributor
timestamp: May 26, 2015, 12:22:09 pm
content: And of course, when IBM did try to do a next-generation PC architecture with MCA and did apply lots of systems engineering and thought, the result was hideous. We produced one MCA_based peripheral, but the experience was so horrible and the market so puny it was very easy to walk away from. Even basic tasks like being able to install and test prototype device drivers were battles - the combination of IBM's tight control over what you could and couldn't do, and the shifting sands of OS/2, was just no fun at all. Quick, dirty and open won in the end.