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Old 23 August 2011, 20:48   #2175
Photon's Avatar
Join Date: Nov 2004
Location: Hult / Sweden
Posts: 4,516
Originally Posted by norecess View Post
Hello guys,

My first post ever on EAB =]

I just bought and installed an ACA630 in my A600. You were all right : my Amiga is faster than ever

I went through no problems, excepted one : with the ACA630 installed, many WHDLoad demos have no audio. Sometimes, sounds pops but still, no audio for most of them. With most of games this is OK.

Would you have to advice to give me to fix my issue? Should I investigate around ACATune software / WHDLoaf pref / valid WHDLoad image ?

I want to precise that I have a legitimate registered WHDLoad key and that I'm only interested in demos (so : no warez request or whatever here).

Thank you

PS. I realize I perhaps posted on the wrong thread. Please can someone point me out what would be the best location in forum?
Originally Posted by Schoenfeld View Post
no, no, no, DO NOT enable chipmem cacheing unless you have a gfx card! It's highly unlikely that you have a gfx card on the A600.

Back when Oliver introduced the feature in the logic, I thought that CPUblit completely switches off the blitter, but in the meantime I learned that only a few functions are replaced with CPU copy-functions. Other functions still use the blitter. If I had known that back then, the function would not be in the card. Chipmem cacheing is a bad idea with a second entity writing to chipmem - the cache would have to be invalidated on a blitter-write, but that cannot be detected on the CPU card.

Norecess, I had problems with games in WHDLoad before disabling chipcache, maybe that's it. "No audio" as description is definitely directly relatable to chipmem handling, as extremely few OCS demos use fastmem for sound, and WHDLoad slaves are likely not modified to handle cached chipmem, as most (all!) accelerators bar chipmem from being cached. Chipmem is shared by ALL chips, not just blitter, so CPUblit [and other inventions] won't make music players work... if you know what I'm getting at...

Originally Posted by Schoenfeld View Post
You're thinking wrong. Burst-fill for cache lines gives a significant performance improvement. Even more than other accelerators, because the ACA1230 and ACA630 cards abort the burst at the end of the cache line instead of wrapping around and completely filling the cache line. The memory controller even decides not to do a burst if the first data word would be the last in a cache line, as this would truly slow down.

Further, with a burst, the first-access-penalty only applies to the first data word. The following data words are transferred within a single cycle - four times faster than the first access. With the ACA's SD-Ram, the 68030 can transfer one data word per cycle. Most (if not all) older accelerators required two cycles per data word because of the slow memory chips of the time.

There's hardly any scenario where burst slows down execution (I could only think of artificial scenarios).

I've arrived at -fastchip OFF -chipcache OFF and everything else at max. It handles everything perfectly, from old CLI commandline utilities to WHDLoad and 3.1 extras.

Does -fastchip ON refer to burst? From what I read it simply states it requires you to know what you're doing before enabling. Or did I misinterpret that and it's about the CPU cli command? Just wondering

Last edited by Photon; 23 August 2011 at 21:16.
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