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A little 486 pearl among the PII swines

D

Druid6900

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Hamilton, Ontario, Canada
Halfway through processing the last load of computers that I got, it seems that it wasn't a total loss.

Besides a bunch of medium to high-end PIIIs for the folks that get computers to people who couldn't afford them, I came across a cute little mini-tower case with a GA-486VS motherboard ( http://motherboards.mbarron.net/models/486vlb3/ga486vs.html ) in it.

One of the VLB slots has a Cirrus Logic (expandable) 54xx VLB VGA card in it while the second of the three VLB slots has a dual channel IDE multi-I/O card in it.

There is also a 10base2 ISA network card in it. For drives, it has a 1.44MB, a 1.2MB and a Quantum 356MB HD.

The board is running an Intel DX2-66 CPU with 16MB of 72 pin SIMM. I forgot to check the cache size when I was running it through Microscope, but, it's probably 256K.

As cute as it is and, although it's not an Apple I, I don't know what I'm going to do with it, so, I'll probably end up breaking it down and putting the parts on my site.
 
Are these things interesting? I've got a bunch of 386s & 486s with & without cases, etc.; what are they good for?

m
 
Hi,
Everytime I see one of those boards, I am drawn to those nice SRAMs used for the cache memory. :) I have a whole rack I got from a gold scrapper as a excess "junk" chips!

Of course, pure ISA machines like that 486 motherboard is useful for test machines for old style floppy disk drives, hard disk drives, ISA cards, memory, etc.

Thanks!

Andrew Lynch
 
Well yes, I do have a few XT/286/386/486 machines around for testing etc and a 486sx has in fact been running my phone logging/CID system since the 486 was new.

And yes, I also pull those 32K SRAM chips (and the sockets) before I toss the MBs; too bad they're not LP AFAIK, good for base RAM in lots of old systems though..

I was just curious why Druid bothered to post about it since he must have a basement full; has discovering a 486DX66 become a rare event? I still see 'em at the curb here and I've got two at the moment ready to go there and another dozen or so awaiting their turn...

m
 
When sorting through junk computers of this era, look out for "fake cache" motherboards. Usually the chips are soldered directly to the motherboard and have "WRITE BACK" written on them... but if you look at the underside of the board, the circuit traces only go in circles between the chips, and don't connect to any real circuitry on the motherboard. The chips themselves are just empty plastic shells. The BIOS is hacked to display "Write Back Cache On" when no external cache is detected.

The "fake cache" scam was that these boards were supposed to have 256K cache onboard and could be upgraded to 512K cache via an optional, proprietary SIMM-like cache module. In reality they were zero K cache onboard and 256K with the cache module intalled. Eventually when the scam was revealed, the cache size was accurately marketed and the fake cache chips were usually removed, leaving only the empty traces running around in circles in a corner of the board.

I have perhaps the most famous fake-cache motherboard, the PC Chips M919, a late 486/5x86 era VESA/ISA/PCI ("VIP") combo board. I do have the "real" 256K cache module and the fake onboard cache chips are intact. It runs my Cyrix 5x86-133 beautifully. Yes, a Cyrix 5x86 at 133 MHz... the chip is really a 120 MHz (40x3), but it runs fine at 33x4. I previously had an AMD 5x86-133 in there and it didn't skip a beat at 150 MHz -- despite reports of much trouble, my VESA Local Bus video card had no trouble with the 50 MHz clock speed. The board's main flaw is that memory above 64 MB is not cached... but for Windows 95 or 98 not heavily loaded with applications, 64 MB RAM is all you really need anyway.
 
Hi!

One technique I use to help sort through scrap chips and such I save from scrappers is to run the chips through a SRAM tester.

I recently got an EasyPro 90B programmer for my birthday and it works to test TTL/CMOS chips pretty well. It also tests SRAMs, EPROMs, and other memory devices. The EasyPro 90B cost about $100 and is a worthy investment if you are considering reusing scrap parts.

Testing to the extent you can will save you grief. Reusing old parts means you WILL find some bad ones. I generally erase all EPROMs and blank test them to see if they are even salvagable. Occasionally I find a bad one, however, sometimes a bad one will slip through only to be discovered when I try to program it and it fails or won't verify.

That's life but better to discover it *before* your restoration project is dependent on it working!

Best of luck! Thanks!

Andrew Lynch
 
Ah. I did make a typo. It should be 24pin or 22pin. 64k x 4 SRAM tag chips definitely exist. I have many of them. What I need are some higher density cache chips for my 386SX motherboard. It is currently equipped with 32kb 25ns SRAM, but I would like to be able to cache 16megs of RAM so I will need to upgrade to 64kb (20ns if possible). The cache layout for my board is kind of strange. There appear to be seven SRAM chips in total. Perhaps four of them are cache, and the smaller three are tags.
 
That mobo looks a lot like one I used to have. The one I had also had a 66MHz 486. It was also in a cute little minitower. Does that one have a "turbo" button, by any chance? Mine had one that switched between 33MHz and 66MHz. Of course, now that I think about it, it may have had an AMD processor...
 
vwestlife said:
When sorting through junk computers of this era, look out for "fake cache" motherboards. Usually the chips are soldered directly to the motherboard and have "WRITE BACK" written on them... but if you look at the underside of the board, the circuit traces only go in circles between the chips, and don't connect to any real circuitry on the motherboard. The chips themselves are just empty plastic shells. The BIOS is hacked to display "Write Back Cache On" when no external cache is detected.

The "fake cache" scam was that these boards were supposed to have 256K cache onboard and could be upgraded to 512K cache via an optional, proprietary SIMM-like cache module. In reality they were zero K cache onboard and 256K with the cache module intalled. Eventually when the scam was revealed, the cache size was accurately marketed and the fake cache chips were usually removed, leaving only the empty traces running around in circles in a corner of the board.

I have perhaps the most famous fake-cache motherboard, the PC Chips M919, a late 486/5x86 era VESA/ISA/PCI ("VIP") combo board. I do have the "real" 256K cache module and the fake onboard cache chips are intact. It runs my Cyrix 5x86-133 beautifully. Yes, a Cyrix 5x86 at 133 MHz... the chip is really a 120 MHz (40x3), but it runs fine at 33x4. I previously had an AMD 5x86-133 in there and it didn't skip a beat at 150 MHz -- despite reports of much trouble, my VESA Local Bus video card had no trouble with the 50 MHz clock speed. The board's main flaw is that memory above 64 MB is not cached... but for Windows 95 or 98 not heavily loaded with applications, 64 MB RAM is all you really need anyway.
Click to expand...

Have one of these board too with a 256k cache stick in the special cache slot...my "fake cache area" is empty from chips though.
Have ran several sys info tools and ctcm but they all have reported no L2 cache so are you sure yours has working L2 cache?
 
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