AHA2790UW has speed-limit problems ?

[Matti Aarnio]

> >   Four Ultra-Wide (SingleEnded) disks on high quality cable inside
> > DEC PWS 433a workstation chassis attached to AHA2940UW host adapter.
> 
> How long is this cable.  How far apart are the connectors in the chain.
> Have you tried using a "forced perfect" terminator?

	That is the original Digital supplied hardware, and so far
	I have not questioned their quality..  The cable assembly
	is made by Amphenol into DECs specification to be used
	in this machine.

> > The Kludge-Cure:
> > 
> >   Lower the speed of the device in the adapter bios configuration
> > utility.  In fact lower them all, and no SCSI-timeout problems appear.
> 
> This would indicate bus signal quatlity problems at high speeds.

	Indeed.  Or perhaps the installation of additional disks was
	not done by a qualified field engineer, and the cable routing/
	twisting inside the chassis is suboptimal -- this is very likely,
	as I am not a qualified field engineer for DEC hardware...

> > Question:
> > 
> >   Is there ANYTHING that is possible to do to in this type of environment
> > so that I could (reliably) run faster disk-transfer speeds ?
> 
> Shorten the cables.  Ensure that the distance between all connectors on
> the cable are equal.  Use a forced perfect terminator.

	Yeah, maybe next time when I open the box I will
	investigate these issues.  Right now it is stable, 
	and I have code to write, and code to compile...

> --
> Justin

/Matti Aarnio <matti.aarnio at sonera.fi>

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