Path: utzoo!attcan!uunet!munnari!mimir!hugin!augean!sibyl!ian
From: ian@sibyl.eleceng.ua.OZ (Ian Dall)
Newsgroups: comp.sys.nsc.32k
Subject: Re: ICM-3216 disk speed
Keywords: System V ICM-3216
Message-ID: <155@sibyl.eleceng.ua.OZ>
Date: 23 Nov 88 12:12:56 GMT
References: <7090@daver.UUCP>
Reply-To: ian@sibyl.OZ (Ian Dall)
Organization: Engineering, Uni of Adelaide, Australia
Lines: 33

In article <7090@daver.UUCP> dlr@daver.UUCP (Dave Rand) writes:
>I have been trying to track down why the System V file system is
>so slow, at least on the ICM-3216. I finally found the reason why.
.
.
.
>I investigated a number of possibilities, and checked a number of
>things. It came down to the fact that the Z-80 (which handles
>the disk I/O on the ICM) had a latency of about 10 milliseconds
>from the time it received a request, to the time it issued an
>I/O to the SCSI device.

Does anyone know why this is? I've tried to glean as much from the
ICM hardware manual and some SCSI bus timing specs and I can't for
the life of me see what should take so long. The SCSI bus arbitration
should be in micro seconds, not milli seconds. I don't know anything
about the 5385 SCSI controller, (for all I know it might be a dog
to drive) but it seems like the Z80 just has to point the 5385 at a
command descriptor block in main memory and tell it to go.

Can the Z80 code be improved?

I heard there were revisions to the PALS and/or  Z80 roms to improve
IO performance. It this true and if so what were the upgrades and how
does one go about ordering one?

I am planning on designing a 32CG16 based graphics card compatable with
the ICM series. National don't have any work going on this do they? I
have no desire to waste effort. Did any peripheral cards for the ICM
series besides the 8 line serial expander ever see the light of day?
-- 
Ian Dall     life (n). A sexually transmitted disease which afflicts
                       some people more severely than others.