Mode 7 M7VOFS latching test (for reference)

[paulb-nl]

I have modified the mode 7 tutorial from https://wiki.superfamicom.org/mode-7-scaling to write to M7VOFS in an HV-IRQ to see when the write takes effect.

If the write is on time then there is a black line above the second row of colored squares like so:

There are different versions of the test slowrom/fastrom and bra and wai. The bra ones wait for the interrupt in an infinite loop.

-:
lda $10
bra -

mode7_tests.zip

The test starts with interrupt H: 0, V:36. Press the L/R buttons to decrement/increment the H value. Press select to reset everything.
Below are the results. The number is the value of the H-IRQ.

SNES APU-01, 1-CHIP-01 with Everdrive:

wai_nops83           1 flicker
wai_nops95_fastrom   3  flicker
wai_nops96_fastrom   1 is too late (no flicker)
bra_nops82           1-6 flicker
bra_nops83           0-3 flicker
bra_nops95_fastrom   1-5 flicker
bra_nops96_fastrom   0-2 flicker

MiSTer with commit a04ac87:

wai_nops83           4 flicker
wai_nops95_fastrom   6 flicker
wai_nops96_fastrom   3 flicker
bra_nops82           6-10 flicker
bra_nops83           2-7 flicker
bra_nops95_fastrom   4-9 flicker
bra_nops96_fastrom   1-6 flicker

Here is an example video of bra_nops_82 on an APU-01 SNES. It starts with the write on time and then I press R 7 times until it stops flickering so the line flickers at H-IRQ 1-6.

2021-05-04.16-08-48.mov

[srg320]

Thanks @paulb-nl.
With your tests I determined the right time by latching Mode 7 registers, which is H_CNT = 11. With this time also no glitches in Super Mario World.

I'm not a fan of adjusting the values for specific games/tests, but I don't see any other option at the moment.

[paulb-nl]

Thanks @srg320. The timings are very close now. These are the results with latching at H_CNT 11:

wai_nops83          1 flicker
wai_nops95_fastrom  3  flicker
wai_nops96_fastrom  0 flicker
bra_nops82           3-7 flicker
bra_nops83           0-4 flicker
bra_nops95_fastrom  1-6 flicker
bra_nops96_fastrom  0-3 flicker