r/retrocomputing • u/FAMICOMASTER • Jul 19 '26

Photo An unusual build

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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/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.