[rescue] Sun Ultra 5 video

Jochen Kunz jkunz at unixag-kl.fh-kl.de
Sat Dec 20 18:07:53 CST 2003

On Mon, Nov 17, 2003 at 12:48:03PM +0200, Meelis Roos wrote:

> The workaround was for CMD640, a completely different chip with a
> special driver.

> CMD646 works fine, it's also present in some Alphas and works fine there
> too. It's nothing special, a normal pre-UDMA IDE controller, normal DMA
> works.
Someone on NetBSD/port-alpha tested an IDE disk on his PWS 500au. 
He connected it to the on board CMD646 IDE adapter and later via 
an IDE SCSI bridge to the Qlogic SCSI adapter. Throughput in pure 
IDE config was low while high CPU load. When the disk was used 
via SCSI the throughput was much higher with less CPU load.
One of the NetBSD developers confirmed this, because the CMD646
can do DMA, but only a quite small chunk of bytes. Thus causing
lots of CPU overhead. => Stay away from ("older") IDE crap. 


Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/

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