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Old 21 October 2019, 21:30   #23
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Join Date: Sep 2006
Location: New Sandusky
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Originally Posted by patrik View Post
If you have no hardware or driver bugs, the mask should be 0xffffffff - no limitations on address or alignment.

Nothing will become better/faster by using a restrictive mask if you don’t need it. It will only make the file system do the transfer in super small chunks via chipmem or similar at really low speed for memory/alignments not matching the mask.

You should have no address restrictions on an A4000 with a Z3 card- all addresses should be usable for DMA. Also, in my experience, Phase5 cards has no alignment restrictions either. You can see if this is the case by choosing mask 0xffffffff for a partition (not boot partition, that is unnecessary) and run a diskspeed test on it and see that it works correctly for byte, word and longword alignment.
DMA doesn't work properly on some device/RAM combinations. In particular some accelerator cards have local memory that does not support DMA from the Z3 bus.
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