MSCP SCSI controller speed
ajp166 at bellatlantic.net
Wed Nov 9 06:27:48 CST 2005
>Subject: Re: MSCP SCSI controller speed
> From: 9000 VAX <vax9000 at gmail.com>
> Date: Wed, 09 Nov 2005 00:23:01 -0500
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>You are right. Those two are not the bottleneck. I measured the actual
>execution time when run "dd if=syssrc.tar of=/dev/null" (photo
>attached). NetBSD 1.5.2 moves 16kB a time. The measured time is:
>4.75ms MSCP-pre-DMA overhead
>0.4ms SCSI overhead
>7ms DMA of 16kB
>4.2ms MSCP-post-DMA overhead
>31ms idle time
>What kills the speed is the 31ms idle time. I blame NetBSD for that.
You need a real time or single user os to get better results. Plain old
dos might do far better or maybe a custom kernal tuned for this use.
>> nor wished to program PCs. That and someone gave me a CMD SCSI adaptor. ;)
>You are lucky. Nobody gives me CMD card. But from now on I probably
>will not need one any more.
It was a lot of years ago, pre epay inflation. That and I got a broken
BA123 microvax with it.
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