more on Ultrix 2.0 / Emulex disk throughput

[Paul Lansky]

Concerning Emulex QD series Disk controller behaviour under Ultrix 2.0 

> In article <615 at hscfvax.harvard.edu>, pavlov at hscfvax.harvard.edu (G.Pavlov) writes:
>    
>     The problem appears to be that DEC decreased the timeout interval on disk
>     requests.  The QD series emulates the MSCP protocol in microcode and does
>     not reply to the cpu quickly enough, thus forcing frequent timeouts.
> 

Can anyone tell me where this timeout occurs? Is it in the uda driver?
its stragegy, start, or interrupt routine?  I have picked through the 
driver a bit and cannot see anything there that would cause this.  The
problem is severe, however.  Under Ultrix 1.1 we were getting a rate of
about 630K bytes per second, and under Ultrix 2.0 this has degraded to
about 250K bytes per second.  I built the kernel from source.
Thank you.  (Both Dec and Emulex seem very tightlipped about this.
The most I could get from DEC was an admission that they shortened the timeout
on HSC to attached disks.  This has nothing to do with our situation, however.)

Paul Lansky
Music Department
Princeton University

paul at phoenix.princeton.edu