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Fixing a VGA issue in Qemu 0.9 (&Kqemu)

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First post, by Jo22

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Hi everyone,

I've just found a solution to an VGA-related issue in my ancient copy of Qemu and like to share it.

The issue was about a garbled VGA output in the APRSDOS application, which also affects synthetic VGAs in Virtual PC 2007 and VB.

The reason I've used Qemu was its higher compatibility to USB serial converters.
DOSBox and several other emulators can run APRSDOS just fine but have trouble with these converters (frame issues, 5-Bit format etc) or don't support serial ports (PCem).

86Box technically was a promising alternative, but the author went full 64-Bit or Vista+, so it won't run on my XP host anymore.

Anyway, long story short, the fix/wirkaround was to load the RAMBIOS utility for the emulated Cirrus VGA. It's part of the Cirrus driver diskettes.
That solved the graphics issues for said application.

I'll add some pictures soon, when I'm home.

Edit: Screenshots attached.

Attachments

  • qemu_vga_garbled_a.gif
    Filename
    qemu_vga_garbled_a.gif
    File size
    16.59 KiB
    Views
    193 views
    File comment
    APRS splash screen (garbled)
    File license
    Fair use/fair dealing exception
  • qemu_vga_garbled_b.gif
    Filename
    qemu_vga_garbled_b.gif
    File size
    20.46 KiB
    Views
    193 views
    File comment
    APRS main screen (garbled)
    File license
    Fair use/fair dealing exception
  • qemu_vga_rambios.gif
    Filename
    qemu_vga_rambios.gif
    File size
    18.24 KiB
    Views
    193 views
    File comment
    Loading RAMBIOS program (VGA141.EXE)
    File license
    Fair use/fair dealing exception
  • qemu_vga_fixed_a.gif
    Filename
    qemu_vga_fixed_a.gif
    File size
    22.47 KiB
    Views
    193 views
    File comment
    APRS splash screen (ok)
    File license
    Fair use/fair dealing exception
  • qemu_vga_fixed_b.gif
    Filename
    qemu_vga_fixed_b.gif
    File size
    27.28 KiB
    Views
    193 views
    File comment
    APRS main screen (ok)
    File license
    Fair use/fair dealing exception

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 1 of 2, by Jo22

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Hi again.

Here some more screenshots of my old copy of Qemu.

Most notably, it starts a Windows popup dialog for my serial port.
Qemu supports one serial port.

My settings..:
[qemu-win DOS.bat]
qemu.exe -L . -m 16 -hda dos2.img -soundhw sb16 -localtime -M pc -serial COM4

Programs..:
qemu-0.9.1-windows.zip
Kqemu-1.3.0pre11-install.exe

I'm also using some exotic memory tools for real-mode DOS (v6.22), to make room for applications.
MAXMEM.SYS driver for M$DOS 7.1 (by CandyMan)
UMBPCI c't 11/95( v3.80, updated by Uwe Sieber in 08/2009)

The usual MS-DOS drivers are left as is.
I've tried to replace KEYB by a smaller version, but this didn't work well.
Either the arrow keys made two movements, or the CTRL+ALT combo for "\" wasn't supported.

The SB16 driver package was being used, too, with the exception of CTCM - it stalled due to the many PnP devices.

To enable serial port's 16550 FiFo, the COMS.EXE program was being used.
It's part of smc.zip archive, which also has an updated Win3.1 serial driver.
But really, any other utility may do as well, suppose.

The RAMBIOS utility of utilv141.zip was being installed at the very bottom of the autoexec.bat.

Attachments

  • qemu_serial_popup.gif
    Filename
    qemu_serial_popup.gif
    File size
    33.29 KiB
    Views
    193 views
    File comment
    The Windows serial dialog called by Qemu
    File license
    Fair use/fair dealing exception
  • qemu_boot.gif
    Filename
    qemu_boot.gif
    File size
    16.68 KiB
    Views
    193 views
    File comment
    Qemu starts..
    File license
    Fair use/fair dealing exception

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 2 of 2, by darry

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Nice! Thank you for sharing.

That strangely reminds me of the issue I was hitting with a Voodoo 3 in QEMU KVM I was finally able to succesfully (mostly) PCI passthrough a real PCI Voodoo 3 2000 to a Windows 98 SE QEMU KVM VM .

In your case, I would guess that a reverse engineered work-alike BIOS image is provided and used by QEMU by default and it has bugs/issues that the actual Cirrus Logic BIOS does not have .

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