maarten@uva.UUCP (Maarten Carels) (06/07/88)
I just looked at SCSI accelerator (just posted in comp.binaries.mac) and
thought you folks would like to share my experiences.
What it does:
Basicly, SCSI Accelerator patches itself into the scsi manager to do
some loop unfolding. This causes some real speedup, especially if you
reformat the disk with another (lower) interleave. I was able to lower
the DistTimer II results of one disk from about 140 to 66 by installing it
and reformatting the disk with an interleave of 2 instead of 3.
So, the speedup is remarkable. On another disk, no speedup was achieved
(but I did not reformat it, backup and restore of some 50 Megs just to try...).
What it does not do:
Although some code is present to patch the write part of the scsi mgr, that
is not installed. The write results of my victim disk increased from 160 to
220. This is to be expected, the interleave is just plain wrong then.
CAUTION:
By the way it works, SCSI accelerator will not work on some disks. Especially
Rodime drives, to be found in SE's (well, some of them) and HD20SC's.
What you can expect of me:
An INIT like this, expected to work on all (well, maybe not all, but on most)
disks, equally active during read and write.
Stay tuned!
--maarten
In real life: Maarten Carels
Computer Science Department
University of Amsterdam
email: maarten@uva
{philabs, decvax, seismo}!mcvax!uva!maartenalexis@dasys1.UUCP (Alexis Rosen) (06/13/88)
ine eater still exist?]
I use a bunch of Q280s on Mac IIs, from CMS. They are the same as Apple's.
Does anyone know what their driver does? I assume from the previous postings
that these drives could be sped up tremendously if the same trick were used.
I understand that Mac II SCSI is quite different from the plus's, but since
this accelerator speeds up blind reads and writes, it seems that the technique
might be useful for the II, as well. On the other hand, I never dug into the
Mac's SCSI stuff, so I might be totally wrong...
/Alexis
--
Alexis Rosen {allegra,philabs,cmcl2}!phri\
Writing from {bellcore,harpo,cmcl2}!cucard!dasys1!alexis
The Big Electric Cat {portal,well,ihnp4,sun}!hoptoad/
Public UNIX if mail fails: ...cmcl2!cucard!cunixc!abr1cmm1@cunixa.cc.columbia.edu (Christopher M Mauritz) (02/22/90)
Sorry if this has been beaten to death... I am currently using a Mac IIcx with an internal 40 meg drive and 2 megs of RAM with an E-Machines Big Picture monitor. I remember reading someting about some sort of SCSI accelerator on the net a while back and didn't really pay too much attention, but now I need the info. Could someone give me the scoop? I'll summarize to the net. The drive in my machine is dreadfully slow. Thanks! Chris ------------------------------+--------------------------- Chris Mauritz |Where there's a BEER, cmm1@cunixa.cc.columbia.edu |there's a plan. (c)All rights reserved. | Send flames to /dev/null |Need I say more? ------------------------------+---------------------------