Windows XP/ Bios Question

I think it depends upon your windows video card driver if it supports the call in the first place under a virtual protected mode DOS window. Basic VGA stuff is probably there, but old VESA calls may not. I know the DOS version of Eagle was not happy with XP since some VESA modes did not work with my graphics card. In protected mode each DOS session gets a copy of memory and the video calls must be emulated by the video driver. Windows probably manages any call in its memory manager.

Most BIOS calls are no longer needed once Windows is loaded. I have a laptop that only can see 136GB disks, But windows can see the whole 256GB. Boot disk is therefor 128GB and a second partion is the remainder. Generally there are no BIOS calls once Windows is booted.

Cheers

what difference would it make?

If you really want to know single-step bios video call and see if the code path and code executed in the window is the same as in dos.

I've used debug.exe over a serial link for that sort of thing in the past.

What if Windows normally intercepts the interrupt and executes its own driver, and puts the BIOS code there just for convenience? :)

Yes, you can single step through it, so at the very least, one hopes they do the same things. If they didn't do that, then the VM must be allowing all interrupts to proceed as normal, and intercepting only the I/O and restricted memory accesses (emulating hardware registers, video RAM and other device buffers if present).

Tim

Maybe.

If the installed video driver is "VGA compatible" (i.e. is capable of emulating a VGA adapter at the I/O-port level), Windows will leave everything up to the driver, which may or may not use the BIOS (although there's not really much point when the driver is tied to specific hardware).

Otherwise, the driver must yield control of the hardware and Windows' built-in generic VGA driver (vga.sys, the one it uses for safe mode or when no other video driver is present) will take over. vga.sys does use the VGA BIOS.

There is some information on the display driver model used by Win2k and WinXP (XDDM) here:

The short answer is not since Win98. In XP it is emulated quite nicely, and in 7 it is a complete sandbox.

Sorry.

?-/