Path: utzoo!attcan!uunet!mcsun!cernvax!chx400!ethz!visinfo
From: visinfo@ethz.UUCP (VISINFO c/o Sascha Schnapka)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: GVP A2000+8 + ST296N - How do you speed it up?
Keywords: GVP MaxTransfer SCSI
Message-ID: <4716@ethz.UUCP>
Date: 11 Jun 90 14:50:18 GMT
Reply-To: visinfo@bernina.ethz.ch.UUCP (VISINFO c/o Peter Simeon)
Organization: ETH Zuerich, Switzerland
Lines: 38

In article <154@coplex.UUCP> dean@coplex.UUCP (Dean Brooks) writes:

>   A couple of weeks ago, I ran across a message that mentioned a bug
>in GVP's GVPprepHD program that caused the Max Transfer Rate to be set much
>too low, causing very bad performance on the ST296N (Seagate 80 MB SCSI) on
>my Amiga 2000.
>
>   Could the author report/mail more detailed instructions on how to change
>the Rigid Disk Block of the hard drive to reflect a new transfer rate?

You can use a Diskmonitor which allows Hard drive access, or a low-level
read tool (like 'Read' by Chris Weber which reads bytes from a device into
memory where you can edit them with a normal monitor).
To be able to use a Diskmon you must write a mountlist entry for your drive
with LowCyl = 0 and HighCyl = 1. Then you can read and modify the Rigid
Disk Block. Each Block has an identifier in the first 4 bytes. You should
look for the Blocks beginnig with PART. A PART Block contains a mountlist.
The detailed description of the structure you can find in the include file
'hardblocks.h'. If you have entered all default values while installing the
drive with the GVP install script, you can find $00002000 in each part block
which is the maxtransfer. Change it to $00020000. Then write the block again
to your drive. The Rigid disk blocks also have a checksum, but you don't
have to correct it. I think GVP doesn't look at the checksum. It worked for me
without recalculating the checksum.

>   Is this indeed a correct solution to the bad performance I am
>getting out of this drive/controller combination?  I know the ST296N is
>a slow drive, but it is not THAT slow.  Any help would be appreciated.

It's not so slow. On a HardFrame we get a transfer rate of 620k/sec with the
ST 296N-1 (28ms) formatted with Interleave 1.


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