[LinuxBIOS] Via Epia-m and VGA Bios emulation

Li-Ta Lo ollie at lanl.gov
Wed Oct 19 19:36:01 CEST 2005

On Wed, 2005-10-19 at 13:59 +0100, Nick Barker wrote:
> I now have some more information on running the VGA bios through the
> emulator on the epia-m
> I have implemented both real mode and emulated VGA initialisation. The real
> mode brings up the vga properly, whilst the emulation does not. The emulated
> version runs to completion and also returns with Carry Flag set which I'm
> assuming means that it has given up trying.
> Using TSC, a performance counter set to count instructions, and a simple
> instruction counter in the main loop of the emulator, I have come up with
> the following statistics for the vga initialisation sequence:
> Real Mode
> ---------
> CPU Clocks = 691,530,971    (600Mhz processor = 1.1 seconds approx)
> Instructions executed = 16,481,875
> Interestingly this gives a clocks/instruction ratio of about 43, which we
> can put down to intensive I/O and which must stall the processor by many
> clock cycles per I/O.
> Emulation mode
> --------------
> CPU Clocks = 4,618,464,706   (= 7.7 seconds approx)
> Instructions executed = 1,946,308,181
> Emulated instructions = 13,756,300

Did you try the user space testbios? As you probably have known,
the VGA BIOS tend to poll some register to wait for some envent,
usually this lead to the same wall-clock time.

Li-Ta Lo <ollie at lanl.gov>
Los Alamos National Lab

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