[Floppertalk] Program to slow down the CPU
jleyda
floppertalk@oldskool.org
Fri, 2 Nov 2001 09:02:09 -0700
> I wrote a program to slow down the CPU. It worked on my AMD and should
> work on any Pentium in real mode. Works by turning off the L1 (and
> L2?) cache. It's at http://satya.virtualave.net/download.html#uncache
>
> I saw on the oldskool website that this might be useful to some
> people.
>
nice work! Yep, you're turning off the L1 cache inside the CPU. This
program will work on a 486 as well, since intel and the clones have used the
same method of turning off L1 since the 486 was introduced.
Flopper uses the same method, once it determines that the machine is at
least a 486. (although I turn off paging in the CPU too, but I have no idea
if that has any additional effect)
I'll ante up another slowdown program I wrote to help with determining the
CPU throttle for the latest version of flopper:
SlowDOS is a TSR that runs under dos or windows and uses the real time
clock's interval timer to provide a fairly smooth throttle. The delay
amount is adjustable on the command line, with values between 1 and 99.
You'll have to play around with your system to find the optimal settings.
SlowDOS also has a /Q command line feature that hammers off the PC speaker
every time the delay routine is called, which will quiet most old games so
you won't wake up your family when playing.
Do a SlowDOS /? on the command line for details.
It's available here:
http://www.silent.net/~jeff/slowdos.zip
Note: Slowdos doesn't fiddle with the L1 cache at all (so it works under
windows) but if you use the two of these programs in conjunction, you should
be able to get that Pentium 800 performing as well as an 8088!
I'm currently researching yet another method of CPU slowdown, which I hope
to be able to start coding over the winter. The RTC isn't the best method
by a long shot since some games want to change the interrupts and possibly
the RTC itself, effectively killing the usefulness of this program.
-jeff!
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