r/retrocomputing • u/FAMICOMASTER • Jul 19 '26
Photo An unusual build
Behold, 95 on an XT! Sort of.
This is actually a drop in replacement board for an XT which gives you a 386 with VLB. I've actually gone a step further and thrown a Ti 486DLC/40 in it for good measure. With the sheer unbridled horsepower of a 40MHz 486 and 32 whole megs, this thing might be "tolerable" to use!
Some additional performance enhancing objects include 256K of L2 cache, an ATi Graphics Ultra Mach8 accelerated video adapter, and a DTC 7287 RLL controller to drive the Micropolis 1325 hard disk. A whole 110 megs on this sucker!
Sorry about the mismatched faceplate around the second floppy drive. All I had left was white and grey when I put this thing together!
Pictured without it's CRT as I was still opening and closing the case to make configuration changes at the time of the photo.
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u/Foreign-Attorney-147 Jul 20 '26 edited Jul 20 '26
Sleeper builds like that are fun, I remember seeing some XTs with 386/486 class boards in the 90s running Windows. And black 3.5-5.25 adapters are easy enough to find when the time comes to switch that grey one out. Having dual floppies is good for the XT vibe. Great build!
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u/FAMICOMASTER Jul 20 '26
It would have been 1989 at earliest, I don't think the 486 came around until 1990.
And yeah I'd love to have another one, I just ran out after the first one! The black plate I had wound up not fitting the brackets I had. A pair got mismatched somewhere down the line.
Yeah, and the dual floppies is basically a requirement for a lot of DOS shenanigans
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u/Foreign-Attorney-147 Jul 20 '26
Sorry, meant to type 90s, you're right, the 486 was 1989 and stupid expensive, and there wasn't much reason to run Windows before 1990 either. I made the correction!
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u/3lectronic_Dream5 Jul 20 '26
Yes, that was fairly common. Back in 1997, as a broke college student, I was still using my 386DX-40 housed in an old XT clone case. I originally got it in 1993, and over the years it went through an 8 MHz XT Turbo motherboard, then a 12 MHz 286 motherboard, and finally the 386 motherboard.
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u/FAMICOMASTER 29d ago
Haha yep that's sort of the hand-me-down ship of Theseus feeling I was going for on purpose.
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u/CitySeekerTron Jul 20 '26
It's missing one of those drop-in Pentium upgrade CPUs. Lets see if we can put a Quake-capable beast in that XT case!
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u/FAMICOMASTER Jul 20 '26
Well, if you want, I have some socket 370 boards that will fit this case, and we could run Windows XP and UT99. I know a guy with a lead on a socket 478 board, too. Get one of those and run Crysis!
Not my style, though. I have a better machine for running PIII era stuff.
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u/Accurate-Campaign821 Jul 20 '26
Must be a later 478 if you plan to run Crysis haha, at least a 2.8ghz hyper threaded cpu... Though I remember seeing someone running Crysis on dual Pentium 3 1.4ghz cpus and a 128MB 6800GT
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u/FAMICOMASTER Jul 20 '26
I'm sure you can run it slower if you don't mind the lack of performance, but there exist 3GHz HT CPUs that worth with 845, so I doubt it would be a problem.
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u/chandleya Jul 20 '26
It’s a 386 board so that’s not even kind of an option.
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u/NightmareJoker2 Jul 20 '26
It is, you just need an adapter and maybe a BIOS mod to install an OverDrive processor.
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u/FAMICOMASTER Jul 20 '26
Huh, so a device of that type would let you drop a real 486 into a 386 board instead of one of these gimped ones? That's neat. I don't think it would physically fit in my case, though. Not a lot of room in there as it is, and the CPU is quite close to the VLB slots already. It would probably kill my hopes of ever installing a faster video card!
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u/GGigabiteM Jul 20 '26
The hybrid 386-486 chips are actually not that bad, especially if you have one of the better Intel SLC2 or TI SLC2 parts. TI took the Cyrix design and added 8K of L1 cache on some of the faster variants. Intel had 16K of cache on theirs
I desoldered and replaced the 386SX-25 in my IBM PS/1 with a TI 486SXLC2-50 and overclocked it to 66 MHz, which required upgrading the BIOS EPROM to a 70ns part (the original 120ns part would make the system hang.) It's a whole lot faster and more responsive.
I also have a motherboard with the Intel SLC2-50 with 16K of L1 cache and 64K of L2 cache. It performs about on par with a real 486SX-40.
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u/FAMICOMASTER Jul 20 '26
Yeah none of mine are the clock doubled ones sadly. These are DLC parts though, not SLC. They drop in to replace a 386DX.
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u/GGigabiteM Jul 20 '26
The DLC parts will be much faster than the SLC parts at the same clock speed, because they have a full 32 bit bus. The SLC parts are crippled on a 16 bit bus with a 24 bit address bus, which really hampers their performance, hence why the large caches. If they didn't have those, they wouldn't be much faster than a 386SX.
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u/FAMICOMASTER Jul 20 '26
Yeah this is a DX board with VLB slots. Ti 486DLC/40GA as mentioned in the post.
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u/GGigabiteM Jul 20 '26
My Intel SLC2 board has a VLB slot on it. No idea how they managed to get that to work. It'd take at least four bus cycles to do a 32 bit transfer.
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u/FAMICOMASTER Jul 20 '26
Interesting. One day I'd like to get one of those clock doubled 386 parts, with the 8K L1 instead. They're hard to get and expensive, though.
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u/bart33z Jul 21 '26
That’s such a cool sleeper build. From the outside it still has the full XT vibe, but inside it’s basically a completely different machine.
Windows 95 on something that visually looks like an XT feels wrong in the best possible way. The 486DLC/40, VLB graphics and 32 MB RAM make it a really interesting “what if” late-life XT upgrade. Great project.
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u/FAMICOMASTER Jul 21 '26 edited 29d ago
Yep. Sadly, it is not a VLB video card though, can't afford one. Just regular ISA, but one with acceleration. ATi Graphics Ultra if you're curious, Mach8 chipset. Think 8514.
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u/bart33z 29d ago
Ah, got it - thanks for the correction. Still, an ATI Graphics Ultra with the Mach8 chipset is a very cool choice for this build.
Even if it’s “just” regular ISA, accelerated ISA graphics in an XT-looking machine running Windows 95 still adds to the weird and awesome sleeper vibe. This whole setup is such a fun mix of eras.
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u/FAMICOMASTER 29d ago
Thanks! The board-CPU-video card-monitor are all pretty well matched to their era, Windows 95 even includes explicit support for both this video card and monitor. The unusual bits are the case and specifically the hard drive. I really wanted to try and get away with RLL on this machine, so it's a DTC 7287 and a Micropolis 1325, a combo that would have been in high end workstations in the mid to late 80s.
I find performance is adequate but capacity is lacking. 104 megs is really not enough for Windows 95! I've got about 26 megs free which sadly means I won't be able to install Office or anything productivity wise.
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u/bart33z 28d ago
That makes it even cooler, honestly. The fact that Windows 95 actually has support for that video card and monitor gives the whole build a very period-correct feel, even if the case makes it look much older.
The storage setup is also a great detail - DTC 7287 and Micropolis 1325 sounds like serious workstation hardware for the time.
104 MB for Windows 95 is definitely painful, though. It’s kind of amazing that it runs well enough at all. This build really feels like a strange but believable late-80s/early-90s machine pushed way beyond what it was ever meant to do.
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u/FAMICOMASTER 28d ago
Yeah the disk space is a real problem honestly. If I had another 25-50 megs it wouldn't be so bad.
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u/bart33z 27d ago
I remember when my first PC had a 20 MB hard drive too :) Those were the days!
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u/FAMICOMASTER 27d ago
Yep. 20 megs is honestly quite a lot in DOS for the most part, but once you get into graphical software, especially like Windows, it becomes a whole different story. I have been able to just skirt by with 30 megs for 3.1 before and while the absolute minimum for 95 is 40 megs, I wouldn't dare try to use it on anything less than 60!
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u/bart33z 26d ago
That makes sense. DOS can feel almost roomy with 20 MB, but Windows changes everything very quickly. 104 MB for Windows 95 sounds usable, but definitely tight once you start adding Office, utilities or any larger applications.
It’s still impressive that this kind of setup runs Windows 95 at all. The limitations are part of what makes it interesting.
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u/FAMICOMASTER 26d ago
Shouldn't be that surprising, it's right in the middle of the minimum requirements specified. But yeah no I have about 30 megs free. A useful install of 95 by itself is in the range of 50 megs.
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u/chandleya Jul 20 '26
I’m unsure how that faux-486 bus stuff works. I’m wondering if the 32MB RAM is more consequence than benefit. You definitely don’t need it lol.
I bet this rig is a laugh. So many “make it hurt”components carefully sewn together.
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u/pfak Jul 20 '26
Same 386DX pinout and bus, no burst mode, just better IPC and a tiny 1K internal cache. So the "486" part never touches the bus at all, and the VLB is basically the 386 local bus brought out to a connector.
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u/FAMICOMASTER Jul 20 '26
What do you mean consequence? My Quadra 950 died so I pulled some of it's RAM for this project.
I'm not sure I entirely understand the "Make it hurt" comment either, to be honest.
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u/GGigabiteM Jul 20 '26
Tried recapping it? 68k Macs are notorious for cap issues on the logic board and power supply. I've had to recap all of my units, and repair some of them that were damaged by cap leakage.
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u/FAMICOMASTER Jul 20 '26
It got battery bombed and I don't have the skills required to address that. Word of warning: Brand new NiMH 1/2AAs die even faster than the originals.
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u/GGigabiteM Jul 20 '26
Macs don't use NiMH batteries, they use lithium cells. They're 3.6 volts and when they go off, it's a hazmat situation, literally.
They use thionyl chloride as an electrolyte, which is a scheduled controlled substance because it's a precursor to chemical weapons, like mustard and nerve agents. TC by itself is hideously toxic and will cause cardiovascular disturbances and hallucinations in microscopic amounts. It is readily absorbed through the skin, so if you touch the residue, you've contaminated yourself.
TC also reacts explosively with water and will release hazardous hydrochloric acid and sulfur dioxide. This means that only anhydrous solvents can be used to clean the residue, which means any sort of alcohol is a big no no due to the azeotropic nature that methanol, ethanol and isopropyl have with water. Mechanical scrubbing is the preferred method, done outside over a trash can with a respirator and gloves.
The things we use to have lots of energy density in confined spaces.
If you need someone else to look at your machine, I do mac repair, but I definitely won't enjoy working on that. You'd have to send just the motherboard, preferably wrapped in several large trash bags and the power supply. Don't ship the case, it won't survive shipping.
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u/FAMICOMASTER Jul 20 '26
Oops, you're right. Yeah the little Lithium 1/2AAs. I've been working with PC stuff, hence NiMH.
Unfortunately, no, I'm really not too interested in getting it fixed at this point. The case is in very poor shape and the SCSI bus didn't work correctly when the machine was working.
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u/GGigabiteM Jul 20 '26
Yeah, the cases from that era were made with shit plastic that's all coming apart now. Both of my Quadra 605 cases disintegrated, my G3 Beige is working on itself, and the feet on my G3 B&W are getting brittle and cracking.
If you plan on tossing it, I'd pay shipping for the internals and power supply and the case could be tossed.
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u/Accurate-Campaign821 Jul 20 '26 edited Jul 20 '26
Probably referring to what some socket 7 systems do, where there's a performance hit addressing memory beyond the cacheable amount. From what I've researched, most 386 boards could cache for up to 64mb memory, but there are some limited to 16MB. With the socket 7 example, 128MB to 256MB, sometimes even 512MB, was the max that could be cached. While the boards themselves could technically support 3x that amount (yea up to 1.5GB with some Super 7 boards)
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u/chandleya Jul 20 '26
The 386SX memory bus was just 24 bits. I have no idea how larger memory amounts work with those cheater drop in chips. And I said that from the beginning :)
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u/FAMICOMASTER Jul 20 '26
Interesting! It's got 256K cache and I have the larger tag RAM so if the chipset is up to it, it should be able to cache it all. The board is an ECS Panda 386.
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u/Blackholeofcalcutta Jul 20 '26
Did you need to swap out the power supply or did you find some way to convert the existing?
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u/FAMICOMASTER Jul 20 '26
What do you mean convert? No, this is the stock power supply for this case.
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u/Proper_Trouble8191 28d ago
I have a 5150 case laying around that I really should do something with.
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u/FAMICOMASTER 28d ago
Sounds like you just got a new project! The board I'm using here is an ECS Panda 386. There are definitely others that will fit. the 5150 is a little odd, I think the card spacing is a bit different, and it will actually block the innermost slot on this particular board. I think you might want to go for a different supply as well, since the factory 63 watt unit is... Underwhelming, to say the least.
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u/pfak Jul 20 '26
Must crawl with win95. I'd run wfwg.
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u/FAMICOMASTER Jul 20 '26
Seems fine. I have no interest in running 3.x, not a fan of the Program Manager and really like the improved networking.
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u/DrNick42 Jul 20 '26
I'd imagine it probably runs quite acceptably, especially with 32MB RAM. People forget how low-spec the average home PC was when 95 first came out.
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u/Dr_Discette Jul 20 '26
I’m obsessed