Williams Emulation Test Suite - old source

This is the older source for the Williams Emulation Test suite. See herefor the latest.

Eventually I will use automated external timing for accuracy, and I will average many passes on the 3 boardsets that I have. I'd also like to see how much temperature affects timing. For now, I timed the tests manually; the variation from test to test is under 1/2%, so that's good enough for initial observations. My current code makes 6 passes of 65,535 loops:

MAME 0145 (64-bit) timed out at 74s for all 6 tests, so it does not take into account mode bit 2, but it is otherwise quite good.

Version 0.1 6809 test suite, 6 blitter timing tests.

Version 0.2 Added 5 more blitter timing tests. I got the width, height, mask and mode bytes from a MAME log playing Robotron, so they should be representative of typical blits. I timed all tests on 2 different actual boardsets, and the longer blits were all within 0.4% of each other.

MAME timed out at 8s, 11s, 15s, 7s and 8s. I need to increase the maximum number of blits from 0xFFFF since the smaller blits complete so quickly. The comparisons aren't as good since my reaction time is a larger percent of the shorter blit time, and the setup for each blit is a larger percent of the total time.

Version 0.5 A little cleanup.

Here are dumps of RAM (0000-BFF7) from an actual boardset after each blit validation pass. Note that the CRCs in the program are bit inverted and byte reversed as compared to CRC-32.

blit validation pass 1

blit validation pass 2

blit validation pass 3

Update- Aaron Giles added a small patch to MAME0145u2 that doubles the timing correction when mode bit 2 is set. With this change, the timing just about perfectly matches my real machine. There still appears to be some timing issue that needs to be found and corrected to make game play more comparable to a real game, though.

Update 2- I wrote a small program to read the 6-bit vertical position register repeatedly and store the results in memory. I compared what I got on my actual boardset to what MAME produced, and noticed a difference. It turns out that MAME specifies 260 scan lines for the Williams games, but the read handler for the vertical position register is only 8 bits. So when the count gets to 256, the register returns 0x00. On my actual game, the register returns 0xFC for lines 256-259, before rolling over to 0x00. This difference would cause any code that waits for the top of the screen to return early.