JOTEGO
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CPS1/CPS1.5 Accuracy
🕑 Added 2021-01-31 10:26:45 +0000 UTCAccuracy of the core; that is what we all want.
I was concerned about the speed of the CPS1 core for a long time. But I needed a reliable way to measure it. I bought the tools to replace the ROMs in an SF2 PCB with my test code. Then, I contacted Grego2D (the author of Final Fight Anniversary Edition) and asked him to write the test code.
The test runs a counter in a loop and shows how many counts can be done in a frame.
The results were appaling: the core was 20% slower in normal mode and 20% faster in turbo mode. MAME, in comparison, is 45% faster. So we were doing better than MAME, but a 20% error was not acceptable.
I corrected the DMA code and got to 15%. Then, I checked over and over the bus wait logic. And, finally, I got it down to 0.08%. Yes, 0.08% error in a demanding test. I think a verified figure of this magnitude deserved a post and a core update.
We still have to test other DMA cases, which may explain the remaining 0.08% difference. But be sure that we will nail this.
Please run the update tool, or look for the files in jtbin. This update also fixes other reported issues.
Comments
Turboman UK
Anyone else using their F5 key too much today?
JOTEGO
Yes, I think the oscillator drift in the old PCB accounts for some of that discrepancy.
Spiff
0.08%.. ?? Isn’t the tolerance level of sync larger than that error margin?... not that I’m complaining :)
