Reverting CHDs to Older format?

[massive88]

I came across the benchmarking site - http://benchmark.mameworld.net/header.html

And was surprised to see the numbers someone posted for Killer Instinct and KI2 using version .067 of Mame.

So to check it out, I nabbed the old binary, but realized that the CHD structure got changed around .094, so my current CHDs are not recognized by the older Mame version.

For the life of me I cant find ways to revert newer CHDs to the old format, only extensive guides on how to go the other way around (make the old new).

Does anyone know how to mess with the CHDs to get them recognized by older versions of Mame?

Thanks...

[SGT]

I don't know how to revert the chd, but you might consider trying Mame version .078 which is actually when the chd format changed I believe.  That's not far from .067 so perhaps you can get similiar frame rates.

[massive88]

I tried older versions of Mame up until the CHD change a few weeks ago (I guessed at the version number above, but I think I tried .079 before), to see if I could get KI running faster.  The official change looks like it went down at .077u1 (private).

Im guessing the numbers posted on that site are bogus, but I cant fully say they are until I can test myself.

Looking at the Maws pages, at the history of the driver I see:
# 0.79u2: Replaced Custom sound with DMA-driven DAC.
# 0.78u4: Changed region cpu2 to sound1.
# 0.74: Changed ADSP2105 clock speed to 10MHz.

I could try 0.78 which should be before that u4 change correct?  Though Id really like to be able to get the earlier one to work just to confirm that it was bogus and give up the fight until I upgrade my processor...

[massive88]

Doh I just checked my recycle bin, I have tried .078, with no noticable increase (not really playable).

So Im back to trying to revert my CHDs.

[massive88]

Found an answer, and was more or less successful with it.

Use chdman to -extract the chd to raw data

Then use hdcomp.exe (chdman's predecessor) to rebuild the raw data into a chd for pre .077 Mame.

At work, KI2 is much faster, with noticeable glitches though, Ill have to extensively test on the Cab at home.