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Saved a Pentium 90 from being scrapped...

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
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Location
The Netherlands
I didn't want her to be scrapped... So I saved this Pentium 90. It is an old AT style motherboard with 72 pin memory modules and socket 5 CPU socket. It has an Intel chipset and the board is made in Ireland. In the meanwhile I've 'replaced' the BIOS battery in the RTC chip with a CR2032 socket. Now I have to find an old IDE hard disk. I should have these somewhere. And I wonder if the CD-rom still works. Funny little project...

Regards, Roland


P90 - 1.jpgP90 - 2.jpgP90 - 3.jpg
 
The reason was simple, commerce: encased in resin = not replaceable = you have to buy a new one = money. But these goofs didn't count on nerds like us :)
 
I've got an old Pentium-75 here which I still use. Important fact is that it's the first PC that I actually owned, I'd had a number before but they were merely borrowed from work, and were under constant risk of needing to be returned.

My P-75 looks very similar to the one illustrated here, not quite identical. Also, mine has the same Dallas chip with the encapsulated battery etc, and this has failed. Not got around to replacing it, as the chip is mounted right next to one of the ISA slots, and this could also make the battery hack too problematic.

However, the machine still works. Complains at bootup, needs date/time entering, and only recognises what the defaults in the BIOS will support, but this is not a serious problem. Main thing is that it will accept my 8bit ISA Roland sound/midi card, which I still need, and it will NOT go in any later machine. So as long as it continues to operate, I'll keep on using it.

Geoff
 
Also, mine has the same Dallas chip with the encapsulated battery etc, and this has failed. Not got around to replacing it, as the chip is mounted right next to one of the ISA slots, and this could also make the battery hack too problematic.
I had a 486 board of that ilk and ran wires off the chip to a coincell battery holder that sat on a piece of rubber at the bottom of the case. It looked dreadful but was effective.
 
That's a pretty solid board and case. That will happily run Windows 95.
It's also in that narrow timeframe where I'm cool with a CF/IDE adapter plugged in because you'll probably never feel the performance ceiling and you can easily upgrade the ram to make sure the system doesn't start scrubbing the swapfile.
 
Many of those systems could take at least a 100-120MHz (maybe even a 133-166MHz) CPU. Throw the maximum RAM and a large HDD at it and put WIN95C on it... it'd be a good machine for some mid to late 90s gaming. Maybe even set up a dual-boot DOS/Win system.
 
That looks exactly like my first work computer in 1996. I moved from a Commodore repair shop to my (still) current company working on Windows NT 3.5 (well, we don't work on NT 3.5 anymore, but it's descendants of course).
 
Nice system, with the Intel Reference Premiere/PCI II board. Has 256k of onboard L2 cache, and the chipset can cache 512MB of RAM. I think these boards max out at 128MB RAM though. The left IDE header is off of the PCI bus, the right one is off of the ISA bus.
If you have any issues replacing the Dallas RTC with a new one, try upgrading the BIOS. The 1992 era original BIOS for these is rather buggy. Your battery bodge gets around the issues with accepting a new Dallas which has more memory than what the original BIOS knows what to do with.

If you want to free up a power supply molex, below the Socket 5 are 2 fan headers, one for "Fan Fast" and the other for "Fan Slow". Fan speed control circa 1994, 2 different headers for different speeds :LOL:
 
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