TMPLee@DOCKMASTER.NCSC.MIL (08/07/90)
To make a long story short, the new HS (DMA) SCSI card doesn't seem to
help at all and actually seems about 10% slower than the original. What
could I be doing wrong?
Here's the long story. Whe I had to get a new disk drive I decided to
pay the $100 and get a new SCSI card as well. Being wary of making too
many changes at once, I installed things incrementally. First I put on
the new disk and got it all re-loaded. The timings with the ProSel16
timing routines were 11.8 msec linear, 26.7 msec random, 1.7 overhead.
I then used the installer (yes, I did) to put in the new SCSI sw. Still
worked, roughly same timing. I then put inthe new SCSI card, but left
DMA turned off because I hadn't yet upgraded my TWGS. The new TWGS PAL
chip showed up today. I plugged it in and turned on the DMA. All
working fine, but the timing is not significantly better: 12.0 msec
linear, 26.18 random, 0.85 overhead. What gives? The drive is a CMS
60Meg ("MacStack") from Quality Computers.
TMPLee@dockmaster.ncsc.miltoddpw@tybalt.caltech.edu (Todd P. Whitesel) (08/08/90)
Doesn't sound like you've reformatted the drive to change the interleave. You should notice a marked improvement with the DMA SCSI once the interleave on the HD has been changed to 1:1 or 2:1. It means backing up and restoring the drive (ugh) but it's worth it. Todd Whitesel toddpw @ tybalt.caltech.edu
whitewolf@gnh-starport.cts.com (Tae Song) (08/14/90)
When you get the faster DMA SCSI cards (Apples and RAMFast) you should low-level format and set interleave to at least 1:1 or 1:2. RAMFast works best with 1:1. Apples would be better something round 1:4, I think. You should test it out for yourself actually. There's lot of factors in setting to best interleave and trying out different interleaves is the only way (at least until someone writes a program to determine the best interleave for a given HD configuration <HINT>>HINT<<HINT> without reformatting 7 times to Sunday). /s