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Old 08 November 2010, 23:32   #321
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Join Date: Jun 2008
Location: Boston USA
Posts: 277
Originally Posted by Schoenfeld View Post
They probably do 4-2-2-2. You can't do X-1-1-1 with normal D-Ram. I make excessive use of SD-Ram features here.

There's two things that may cause a burst to be slower:

1. you start it when it doesn't make sense (at the end of a cache line)
2. you run it all the way through, 4 longwords, "no matter what".

My ACA cards will only start a burst if it's NOT at the end of a cache line, and they stop a burst if the end of a cache line is reached. Call it a "dynamic burst", because it can be 2, 3 or 4 cycles long, depending on what's most useful.

All this stuff is described in the original Motorola literature. I'd be surprised if Phase 5 has not implemented this, because it's not that hard to do.

Yeah I have the moto 020 and 030 user manuals. I was using an aligned copy which is why I found it odd. A sequential memory copy with data burst off is considerably faster than without on those old cards.
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