Compaq Deskpro 8086 and NEC V30

[dhau]

Hi folks, I replaced 8086-8 with a NEC V30 in my Compaq Deskpro (very first Compaq desktop).

It worked, but on each startup it would show error 301 - "keyboard stuck". Otherwise it would boot and work with the Key Tronic keyboard (model E03601QL).

I tried a few other XT keyboards, but they actually didn't work at all, flooding keyboard controller with continuous key presses.

After I switched back to Intel 8086-8 CPU, all issues with keyboard were gone. I use BIOS rev. J.

I suspect the problem is in BIOS code, some sort of assumption of how many CPU cycles a certain set of instructions take to execute and access to I/O ports. I assume if someone to find out where it is and patch by inserting a few NOPs, the problem would be gone.

Question for other Compaq Deskpro owners:

1) Did you try to switch to NEC V30 CPU? Did it work?

2) If it worked for you, what is the revision of BIOS and model number of motherboard?

Thank you!

 

[resman]

I have two Deskpros with V30s in them. Using the original keyboard and a Compaq extended keyboard. No issues, even running XENIX86. I'll have to check the BIOS versions later as they're a little hard to get to at the moment, but I recall them both being later models.

 

[dhau]

I have two Deskpros with V30s in them. Using the original keyboard and a Compaq extended keyboard. No issues, even running XENIX86. I'll have to check the BIOS versions later as they're a little hard to get to at the moment, but I recall them both being later models.

Thanks for confirming it works for some folks... If you can, please check the bios date in CheckIt. Mine was from 1987.

I have 3x V30 chips and a few original Compaq BIOS chips. I'll try them out, see if it helps.

 

[resman]

Checkit 2 couldn't identify a date on the BIOS. Here are some images from the motherboard:

 

[dhau]

Checkit 2 couldn't identify a date on the BIOS. Here are some images from the motherboard:

Thanks! CheckIt 3 does show the BIOS date. Based on this: https://www.pcjs.org/machines/pcx86/compaq/portable/rom/ it is Rev. H. I'll try it out.

 

[resman]

Thanks! CheckIt 3 does show the BIOS date. Based on this: https://www.pcjs.org/machines/pcx86/compaq/portable/rom/ it is Rev. H. I'll try it out.

I see Rev F on that list for the ROM #. CheckIt 3 still responds Unknown for date

 

[Amygdala]

Sorry this information is of no help: but Compaq also put out the first 386 PC, September 1986, and it was also "Deskpro". So, there were a few generations of Deskpros, I just thought I'd throw that out there for anyone who might have thought all Deskpros were 8086s. It's kind of interesting Compaq didn't put out 8088s (at least not desktops). They seemed really motivated to put out the best clone tech they could.