Matthew Dillon <[EMAIL PROTECTED]> writes:

> :Two things I've noticed:
> :1) my cdrom delivers about 2M/s which is the same as before DMA.  Is
> :the improvement only in cpu usage or should I be seeing a speed
> :improvement too? 
> :
> :speed tested with:
> :dd if=/dev/racd0c of=/dev/null bs=64k count=320
> :(I get it to spin up with another dd before this test)
>     Well 2MB/sec == 14x CDRom drive.  Is it a 14x CDRom drive?  CDRom
>     drives are typically limited to how quickly they can get data off
>     the platter.  A faster bus transfer will not improve that.

I should have mentioned that ... it's a 32x cdrom.  dmesg says it
claims to be able to do 5515 KB/sec. 

I've played around with using dd ... skip=n to reposition which part
of the cd I'm reading and I've seen some much better speeds on the
outer tracks (I think I now recall that cd's start numbering from the
inside tracks, don't they?).  So you're probably right that it's just
the rotational speed that I was seeing.

Kevin Street

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