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Realtek RTG3105E in XT system

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    Realtek RTG3105E in XT system

    Hi folks, I got a Realtek RTG3105E VGA card that should work in XT style ISA slot, but it doesn't.

    Realtek RTG3105E opt.jpg

    Card has two jumpers JP1 and JP2. JP1 is either open or closed, JP2 has three pins, so it can be: no jumpers, 1-2, 2-3. I tried all combinations and it didn't work in XT, but works fine in 486 with 16-bit ISA. What could it be? Is BIOS not 8088 compatible? How would I detect that?

    Does anyone have Realtek RTG3105E VGA card that does work in XT system? If so, what is your BIOS?

    Thank you for any help or suggestions.

    #2
    Are the switches on the xt board set properly? There is a setting that tells the xt if you've an ega or vga card. Just Google ibm xt dip switches
    Nothing beats the roar of a 36yr old drive coming to life after a decade in storagg

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      #3
      I have a very similar card and it works fine on two XT clones. At least on mine, I did not have to touch any jumper It autodetected bus type. Revise the mb video switches (both should be off for ega/vga)

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        #4
        Originally posted by dieymir View Post
        I have a very similar card and it works fine on two XT clones. At least on mine, I did not have to touch any jumper It autodetected bus type. Revise the mb video switches (both should be off for ega/vga)
        I do have switches 5 and 6 ON, and all my other EGA and VGA cards work fine.

        Can you dump the VGA BIOS from your card please? I want to try it out on my card. Here is how to dump: http://mess.redump.net/dumping/dump_bios_using_debug

        I also plan to try it on XT with V20 CPU. May be my BIOS is using some 286 instructions.

        Update: I found some bios here http://chukaev.ru54.com/video_en.htm - I'll dump my card bios and compare it to this one, if it's different, I'll try to replace the bios.
        Last edited by dhau; April 5, 2021, 06:49 AM.

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          #5
          I tried this video card on an XT with V20, and it also didn't work. So it's not the 286 real-mode instructions in BIOS... I'll try to compare the photo of my card to those I can find online. Maybe my card is missing some components required for 8-bit operating mode.

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            #6
            Does this card work in other machines? Could be the card is toast.
            Nothing beats the roar of a 36yr old drive coming to life after a decade in storagg

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              #7
              Originally posted by k2x4b524[ View Post
              Does this card work in other machines? Could be the card is toast.
              It works fine on 486 system. I'll try it on a 286.

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                #8
                It is entirely possible that card doesn't support 8-bit operation
                Nothing beats the roar of a 36yr old drive coming to life after a decade in storagg

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                  #9
                  This appears to be the stason.org spec sheet for that card. https://stason.org/TULARC/pc/graphic...-V2-91024.html

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                    #10
                    If it didn't work in any computer I'd suggest trying to reseat the DAC and BIOS chips, I resurrected all of a batch of "dead" OAK VGA cards by doing that, but since it works in the AT bus machine I'm without clue. Have you tried it on just one specific XT clone? Maybe it's an incompatibility with that one machine, because based on random forum trolling it seems like those RealTek cards mostly work for other people.
                    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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                      #11
                      Originally posted by Eudimorphodon View Post
                      Have you tried it on just one specific XT clone? Maybe it's an incompatibility with that one machine, because based on random forum trolling it seems like those RealTek cards mostly work for other people.
                      I'll try to reaseat the RAMDAC and BIOS chips, but it works fine on 486, so probably not an issue. A lot of folks with identical card report it works in XT for them. I tried in two XTs so far, a basic 5160 with 8088 @ 4.77MHz and a Turbo XT clone with V20 @ 8MHz. No luck.

                      At this point I can only think of two things:

                      1) expand RAM to full 512K (all folks who reported it working in XT had full 512K). Not sure this will help, but who knows?
                      2) dump BIOS with debug on 486 and compare it to what other folks have. Perhaps my BIOS is different.

                      Originally posted by bolex View Post
                      This appears to be the stason.org spec sheet for that card. https://stason.org/TULARC/pc/graphic...-V2-91024.html
                      Thank you very much! This is very useful.

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                        #12
                        I'm sorry for the long delay in the answer but I was busy with real life ... Currently I do not have the card installed but, as you can see in the photos, it's very much like yours:

                        Card Image

                        The BIOS chip:

                        BIOS image

                        It, indeed, has 512KB of ram installed but I do not really think this is the origin of the problem since 256KB is the "standard" VGA memory size.

                        I've seem truckloads of those cards all with the same 3.C10 BIOS so nothing special on this particular specimen but I'll try to extract the BIOS if you're still interested.

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