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Author Topic: New CopyMem & CopyMemQuick patch  (Read 4812 times)

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Offline itix

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Re: New CopyMem & CopyMemQuick patch
« on: September 07, 2011, 10:02:42 PM »
Quote from: matthey;452505
Your posts are not too helpful mongo. Do you care to spread some of your great intellect with a reason or two or are we just incapable of understanding such superior intelligence? What ChaosLord said here is not worded well but practically correct. A better wording might be...

"Apparently move16 should not be used on Amigas lacking an MMU unless all the caches are off. So if you have a 68EC040 or 68EC060 then you are screwed."

"For this reason we cannot recommend that anyone use a 68EC040 (or any future 68000 series CPU that has no MMU) as the CPU on a Zorro III bus system."

Anyway, didnt AmigaOS have big issues with 040/060 when DMAing to fast memory? Those pre/postdma calls... Because of caches the CPU could accidentally trash data and DMAing to fast ram would only work if you had an MMU. This is completely unrelated to move16. And it would be only an issue if you had a devices with DMA support.

(Geez, I have lost so much information about Amiga in these years....)
« Last Edit: September 07, 2011, 10:06:26 PM by itix »
My Amigas: A500, Mac Mini and PowerBook
 

Offline itix

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Re: New CopyMem & CopyMemQuick patch
« Reply #1 on: September 12, 2011, 04:50:36 PM »
Quote from: psxphill;659056
You can flush the cache without a MMU. So it really shouldn't be a problem.

 
It won't help because caches could get dirty again.

Quote

No idea why I thought this was a current thread :-)


Me neither :)

@matthey
Quote

Maybe you are thinking of the Buster chips that caused DMA problems on 4000s? I vaguely remember a bug in the AmigaOS cache flushing too. Either way, they should be fixed or worked around and shouldn't affect move16.


I dont think it has anything to do with Buster... if you DMA to fast ram CPU wont know about it. It could accidentally trash data crossing cache line boundary.
My Amigas: A500, Mac Mini and PowerBook