EclaireXL

Related post: http://atariage.com/forums/topic/118448-implementation-of-pokey-2-tone-filter-in-emulation/page-3#entry1449990

Been measuring cases on the scope...

Confirmed the extra cycle delays described in that forum post on my 600XL. Confirmed missing on the EclaireXL implementation.

I was concerned that my clocks were off at first since I was running in VGA mode, but that changes vsync slightly (50Hz vs 4.86Hz) which of course also impacts audio frequency:-) Debugging in RGB mode gives a perfect match.

A 2 cycle delay on the reset fixes both the 4 cycle and the 9 cycle case.

Now to check this specific example!

Nope, seems to be some interaction with the noise filtering. I wonder if the delay also needs applying to the pulse from the timer, that then hits the noise filter.

I found if I pokey 53775,11+128 on the Atari then it matches the Eclaire output. Unfortunately forcing the serious output on eclaire to 1 or 0 does not change anything. Still its something to go on!

I have audio test pcbs now to allow synchronised writes to pokeymax vs pokey. Which should help track down this kind of thing.

This was fixed following investigation and a simple test case/detailed spreadsheet from Synthpopalooza.

I used these new audio test pcbs and a cycle exact fpga comparison program to check it against the real pokey.

Incidentally I found another few small intermittent cycle differences which I'll be able to track down with this too.