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Using Multiple CPU Cores in DOS? (Miscellaneous)

posted by tom(R) Homepage, Germany, 15.09.2011, 14:43
(edited by tom on 15.09.2011, 18:34)

> > if in real mode,
> > if FreeDOS
> > switch to protected mode, copy data, switch back to RM
> > if MSDOS
> > use unreal mode and copy data
>
> How do you figure there's going to be a huge difference between switching
> modes yourself and having INT 15.87 do it for you? Other than the mode
> switches, INT 15.87 doesn't need to do anything that takes a lot of time.

may be 'other then mode switches' is the answer, and it's fairly well known that BIOS int15.87 is SLOOOOW.

anyway, on an 500 MHz K6, I'm able to call XMSMove() 590000 times per second in real mode (for blocksize 4..64). that should be fast enough for a keyboard handler (and even EHCI USB should you ever implement this)

in protected mode, this very much depends on the DPMI host, as you are accessing 'memory' that does not exist, so the DPMI host has not necessarily page table descriptors for this memory allocated, and must somehow emulate that. I remember that FD-EMM386 was modified to handle this, but forgot the details

P.S: my I7 920 in real mode can execute 1,900,000 XMSMoves per second

P.P.S: use www.drivesnapshot.de/freedos/himem.exe and run
HIMEM /TEST
to measure these numbers;

 

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