Adaptec 1542 performance

Stuart Lynne sl at van-bc.UUCP
Sat Oct 14 07:28:05 AEST 1989

I'm evaluating an Adaptec 1542 SCSI controller with a Miniscribe 3130 SCSI
drive under SCO Xenix 2.3.2 GT. This is in a 25Mhz 386 box from Monolithic
Systems (a pretty generic C&T style board, no cache).

So far the results are pretty dismal. Just over 100kbps throughput.

I've patched the kernel ad_xfer to 1 for 6.7Mbit DMA and setup the board in
various ways. 

The 386 is running at 25Mhz, with the bus at 12.5Mhz and the DMA clock at

I use a simple test for timing the effective throughput for reading:

	time dd if=/dev/device of=/dev/null ibs=100k obs=100k count=100

My WD1006SR2 on the same system does the above in about 25 seconds for the
raw device, and 26 for the cooked device.

The Adaptec does it in about 94 seconds for the raw device and 180 for the
cooked device.

I've also tried a CDC SCSI drive with precisely the same timing results.

Is this normal or do I have things setup wrong?

Stuart.Lynne at ubc-cs!van-bc!sl 604-937-7532(voice) 604-939-4768(fax)

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