dos program like prime95 to stress emulated CPU ?

[wyvernshill]

Ok, i was thinking ... (perhaps a bad idea)

Some games require less cpu than others so sometimes you make a base machine with a processor in pcem that might be too fast for your own host system to handle.

Now i was thinking, is there a dos utility that stresses the emulated CPU to it's maximum so that you can dial in the "perfect machine" to make in pcem cpu-wise ?

For instance i can run a P2-233 perfectly with doom, descent and others but then some other games might be too much for your system. (only daggerfall for me atm)
So perhaps the "correct" machine for me would be more like a P200 MMX or even less ?

Anyone know of such a tool in dos ?

Thanks.

[A. Naim]

So related to this and the other thread you made; but the other thread is Daggerfall-specific, so I put it here:

PCem AMD k6; CPU Internal Cache on/off, and 166MHz vs 300MHz, on a Ryzen 2700x with 3200MHz RAM; letting the machine idle in the Civ 2 main menu:

CPU Internal Cache on: 166MHz/100% vs 300MHz/63%
CPU Internal Cache off: 166MHz/100% vs 300MHz/97%

My guess is that emulating two caches (CPU internal and CPU external) messes with the hardware CPU caches, due to the need to keep two datasets active, and shuffle data between them. With the emulated external cache on, and the emulated internal cache off, my guess is that the instructions can stream more directly through the emulated CPU.

tl;dr - You might be able to run a much faster CPU by turning your emulated CPU's internal cache off.

[SarahWalker]

Turning off 'internal cache' is a proxy for disabling the dynamic recompiler. PCem doesn't have any cache emulation.

[A. Naim]

Turning off 'internal cache' is a proxy for disabling the dynamic recompiler. PCem doesn't have any cache emulation.

That does leave me confused over where the speedup is coming from, then.

[SarahWalker]

Interpreter only implements up to 486 instruction timings, hence a K6 with the internal cache turned off will be performing roughly like a 486 at that clock speed.

[ecksemmess]

Interesting, thanks for clarifying this Sarah. Just to be sure I'm understanding correctly: you're saying you've implemented a dummy "internal cache enabled" property for the emulated CPU, toggle-able via the emulated system's BIOS? And that in lieu of anything to do with actual cache emulation (since no such emulation exists in PCem), you've rigged that property up to switch the emulated CPU over to the interpreter when disabled, thereby turning the emulated system into a glorified 486?

Hopefully not seeming too dense here with this question - as described above it does seem like it could open up some interesting back-door debug possibilities but I'm not sure if that was the intent.

[A. Naim]

Which indicates that the problems reported with Daggerfall in this post:

viewtopic.php?p=14897#p14897

are due to a PII/233MHz CPU being too fast for Daggerfall.