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XT harddisk stopped loading upon upgrading Cyrix 8086 with NEC V30, AmstradPC1640

H

heribert12

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Joined
Jul 17, 2019
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4
Hello,

I tried to upgrade my AmstradPC1640 with a NEC V30 (8Mhz, V30-8). After I put in the CPU, the harddisk bios (I use a SVC Gold Card hard-card, 31MB) stopped loading; the harddisk is not seen at all. I was initially worried to have damaged something, but once I put back my original (Cyrix) 8086-2 (8Mhz, its a fully intel compatible clone), everything was back to normal.

My question: Did I get a faulty Nec V30 (its a new chip), or, is there any reason for this behaviour? If anyone knows the SVC Gold Card, do I need to change jumper setting if working with a NEC v30 perhaps?

Any indication helpful! Cheers to the XT enthusiasts.
 
heribert12 said:
Hello,

I tried to upgrade my AmstradPC1640 with a NEC V30 (8Mhz, V30-8). After I put in the CPU, the harddisk bios (I use a SVC Gold Card hard-card, 31MB) stopped loading; the harddisk is not seen at all. I was initially worried to have damaged something, but once I put back my original (Cyrix) 8086-2 (8Mhz, its a fully intel compatible clone), everything was back to normal.

My question: Did I get a faulty Nec V30 (its a new chip), or, is there any reason for this behaviour? If anyone knows the SVC Gold Card, do I need to change jumper setting if working with a NEC v30 perhaps?

Any indication helpful! Cheers to the XT enthusiasts.
Click to expand...


Hello there, not sure if you get any answers with this? I hope you've found a solution. I too am having problems upgrading a 1640 with a V30.

I've just got hold of a NEC uPD70116HCZ-10.

When in the 1640 I get a Faulty System Ram message. Initially I thought that perhaps this was true (I'd previously replaced one of the 41256 RAM chips) but have found that swapping back to the original 8086 allows the machine to boot with no error messages...

Is it possible I have a faulty V30? Is it possible the V30 is actually finding faulty RAM that the 8086 is not?

It's a shame as the v30 and then 8087 are the last tweaks I wanted to make. I've got an additional RAM board in it which gives me some upper memory to load things high into, a couple of CF adaptors on an XTIDE card, a working SB16 for adlib games and an 8 bit ethernet card. It's the 1640 of my childhood dreams!
 
Hello,

we may have the same problem. I also got a RAM parity error that disappeared once I put the Cyrix chip back. It did not show up each booting, though.

It gets interesting: I got hold of a slightly newer (1988) PC 1640. It came with an original Intel 8086-2 . I put the NEC chip in this one: and it works without any problem!!

Is the cyrix after all addressing the bus in a different manner? would you be up for a test to put an original 8086 in your PC1640 and see if the error comes up again?
Are there ways to flush the 1640 bios rom, with the 1988 version that supports the NEC v30?
 
I've never heard of Cyrix making any CPUs prior to the 486SLC and 486DLC. Math co-processors, yes, but not CPUs. Are you sure you aren't confusing it with an 8087 chip?
 
Hi! Thanks for the link. The problem described for the IBM 5160 indeed reads very similar. (and no, I have not confused the CPU with the coprocessor, my 8087 is a genuine Intel Ceramic :) ).
I could read the bios from the newer PC1640 and put it on the older one, if there is a tool that could do so. Btw there are more differences, the newer PC1640 boots from a 720k disk, while the old one only from a 360k.
Any idea about a bios read/flash tool that could work in a PC1640?
 
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