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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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A few questions about Compaq Deskpro 8086

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    A few questions about Compaq Deskpro 8086

    Dear VCF, I recently bought a mostly working Deskpro 8086. It had a bad floppy/lpt card and the red/green led only showed red, looks like green part of it died. BIOS is Rev.G

    Here are my questions, thank you for taking your time to answer!

    1) Deskpro BIOS starts in green (8MHz) mode, but switches to red mode (4.77MHz) just before booting DOS. Is this normal?
    Usually Turbo XT computers start in Turbo mode and you can switch to 4.77. Is it possible to patch bios? If not, is there a tool to switch speed back to 8MHz I can stick in autoexec.bat?

    2) VDU would only output proper CGA text mode on DB-9 if I set switched 5 and 6 both on, like for EGA/VGA. It outputs proprietary frequencies for switches 5/6 set to on/off. Is this the same for all? Or should I upgrade bios to latest Rev J?

    3) The dual color led is half dead. Red ok, green is not working. Can I replace it with a modern equivalent? What should I look for?

    4) Original fan is rather loud. Did anyone try replacing it with a modern 120mm 12v fan? How is your experience?

    5) 8086 CPU is soldered in. Is it worth trying to desolder it to put a NEC V30 instead?

    Thanks again!

    #2
    1. My 8086 boots with the red LED lit up and when it finishes booting its green. There is a keyboard combo you press to change the speed. Looking in my original docs since its been months since I messed with my Deskpro, use CTRL + ALT + \ to toggle the speed between FAST ( Green is 7.14 mhz) or SLOW (Red is 4.77 Mhz).
    2. I would have to take the cover off to see.
    3. Don't know.
    4. You have to be careful with the fans, some have 110v fans and some have 12v fans. I have three or four power supplys and there is a least one that has a fan thats 110v.
    5. It might be worthwhile to solder in a socket, mine has a socket that is original and I went with a V30 cpu about 25 years ago since it was easy. To be honest it's hard to tell except when I needed a VGA card that works with a V30 but not a 8086 cpu.

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      #3
      Pic of some keyboard commands from my manual.

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        #4
        Compaq versions of MS-DOS will switch the DeskPro to fast (green) mode during boot. The Compaq version of MODE.COM can switch the speed, too.

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          #5
          Thank you very much for your reply Klee

          Would you be able to take pics of all manual pages?

          It looks like if I use Compaq DOS, I can put "mode speed" command in autoexec.bat to switch to 8mhz, as per page you shared above.

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            #6
            Congrats on getting an original Deskpro!

            Yes, just use Compaq MS-DOS and it’ll switch to 8MHz on boot up.

            Interesting about the LED. Never heard of that happening before and don’t know where you could get another unfortunately.

            About the fan, I personally wouldn’t bother replacing in unless it’s making unusual noises (like grumbling). Those are pretty good quality fans and I like my old computers noisy anyway!

            And for the CPU socket, I probably wouldn’t unless you are really comfortable with soldering.
            Compaq - It simply works better

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              #7
              Originally posted by compaqportableplus View Post
              Interesting about the LED. Never heard of that happening before and don’t know where you could get another unfortunately.
              I found out it's called "bi-color red green led" and the usual places are chock-full of them, 100 pcs for 5$. Or 10 pcs for 4$. It's how they get you Anyway, I swapped led from the dead Deskpro I bought earlier, so I'm ok. I will need a working bi-color led if I get that dead Deskpro to work.

              I agree about desoldering, I'm not comfortable, so I'll leave it be.

              I now struggle to get original Compaq 3.5" 720KB drive to work as B:. May be my bios is too old to do it (G, 1985). Need to try J from 1987.

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                #8
                Upgrading BIOS from G to J didn't fix drive B: issue I have. I suspect the drive itself may be bad.

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                  #9
                  My Compaq Deskpro 8086 in Turbo mode runs at 7.16 MHz. This is reported by both Norton Utilities 5 SysInfo and by CheckIt 3.0.

                  Is this normal? Do other people also see it at 7.16MHz? Or 8MHz? Please let me know. Thank you!

                  Edit: apparently it's normal. Wikipedia says it's running at 7.14MHz: https://en.wikipedia.org/wiki/Compaq#Compaq_Deskpro

                  But here, they say it's 8MHz... https://en.wikipedia.org/wiki/Compaq_Deskpro

                  Comment


                    #10
                    Originally posted by dhau View Post
                    7.16MHz? Or 8MHz?
                    Quoth Creative Computing in 1985: "The Deskpro specs are equally impressive. Its 16-bit 8086 processor normally runs at just over 7 MHz and executes most CPU-intensive tasks about twice as fast as standard IBM PC."
                    https://www.atarimagazines.com/creat...versus_IBM.php

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                      #11
                      Originally posted by vwestlife View Post
                      Quoth Creative Computing in 1985: "The Deskpro specs are equally impressive. Its 16-bit 8086 processor normally runs at just over 7 MHz and executes most CPU-intensive tasks about twice as fast as standard IBM PC."
                      https://www.atarimagazines.com/creat...versus_IBM.php
                      Going way back was there not some issues with the Desk Pro's HD's not being fully compatible? Or maybe or may be it was the controller/cabling.
                      Surely not everyone was Kung-Fu fighting

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                        #12
                        Originally posted by Agent Orange View Post

                        Going way back was there not some issues with the Desk Pro's HD's not being fully compatible? Or maybe or may be it was the controller/cabling.
                        There wasn’t any compatibility issues with the Deskpro. Think of it as basically a desktop version of the Compaq Portable, but with an 8086 instead of an 8088.
                        Compaq - It simply works better

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