14 Nov
2007
14 Nov
'07
3:17 a.m.
From: rtellason at verizon.net> > This is where
I get a little puzzled sometimes. Like that BB2 I mentioned, > that uses DMA to send a
string of bytes to the disk controller chip rather > than using the processor to do
those transfers. Why is not immediately > apparent to me since the processor isn't
doing anything else at that point > anyhow...>
Hi
I once wrote code to take avantage of DMA to disk. I was doing a search
that required a case insensitive search. I found that on the processor
I was running, it took almost as much time to read a track as it
did to search the data on the track. I'd only have to wait, doing
nothing on the first read. After that, I would just have to wait a
little while until the next track was read, because I'd started
the second DMA before I started searching the first buffer.
In a multi user system, one could be handling all kinds of
activities while the buffer was being loaded.
Dwight
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