Subject: SCSI performance tuning on 5000/{125,133}, 5000/25
To: None <port-pmax@NetBSD.ORG>
From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
List: port-pmax
Date: 04/09/1997 20:20:39
On Monday I committed a fix for a performance bug on the 3MIN
(5000/125, 133) and MAXINE (5000/20,25,33) DECstations.

The ioasic-attached 53c94 SCSI chip on these machines was being
initialized for a 12.5 MHz clock speed (correct for a TurboChannel
option card), when they should have been initialized for a 25MHz clock

I also disabled the warning message about bytes left over in the FIFO
after a DMA output operation.

Together, these changes should put the SCSI performance on a 3MIN or
MAXINE back to what it was in pre-1.2 days.  I'd be interested to hear
iozone or bonnie comparisons versus 1.2C, from those who reported a
decrease in SCSI throughput since 1.2 or before.