First post, by Jo22
- Rank
- l33t++
Hello everyone,
I've got a Nixdorf 8810 M35 PC/XT class machine @ 4.77MHz.
You can see the specs here (site of another M35 user):
http://www.cpu-galaxy.at/complete_systems/Nix … ixdorf_8810.htm
Recently, I thought about upgrading it *just a little* with a NEC V20..
Not for speed, but rather for the 8080 emulation mode and the additional 186/286 instructions.
Unfortunately, it did not work. 😢
After I replaced the ceramic NEC D8088D with a NEC D70108HCZ-16,
the machine stopped working. HDD spun up, but no POST, not signs of life on the keyboard.
After re-installing the old 8088, it came back to life. Gratefully! Phew! 😅
Out of curiosity, I also installed my dad's 30 years old MBL8088-2 (8MHz) and
it worked flawlessly (I even ran some diagnostics/benchmark software).
What did I wrong ? I know, the 16MHz version of a NEC V20 isn't an ideal match,
but could it really cause such behavior ?
I always was assuming the MHZ rating was just describing the
maximum tolerance and should work with anything above the base frequency of 4MHz.
What could it be ? Perhaps the BIOS is/was not V20 compatible yet ?
The machine came out in ~85, a year after the V20.
I thought about the possibility of an unsupported i8086 instruction or behavior
that could make the V20 halt, but I can't check that myself.
So I'll attach a dump of the firmware for analysis.
Maybe someone else can have a quick look inside ?
Or maybe the chip is just a fake part anyway ?
But if the chip was indeed fake, wouldn't it have killed the machine ?
Has anyone any idea ?
Thanks in advance!
Best regards, Jo22
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