[SunRescue] About Sun3 and SCSI

[Peter Koch]

Hi!

There's a lot of mystery tale going on...

Here are my $0.02 ;-)

>   3/50         15.7MHz or thereabouts

Who said this? From my experience, the CPU clock of the 3/50
is from a 60 MHz oscillator, divided by 4. This gives 15MHz. 
The FPU runs at 16.67 MHz (33.33 MHz divided by 2).

The frame buffer of the 3/50 uses main memory and steals
cycles, so the machine will be a little bit slower than
15 MHz. And: My 3/50 all have a 15 MHz CPU!

>   3/2xx        25MHz
>   3/4xx        33MHz

The FPU of the 3/260 runs at 20 MHz.
Both servers have 64 kB second level cache. The 3/470 does
have an I/O-cache!

>Don't know. To be honest, I've never had very good luck with Sun-3
>SCSI controllers, even under SunOS.

Um, yes, these are beasties. They seem to interact more or 
less with all other cards in the machine. They work best,
if the machine does not contain other boards (ALM, MCP, XY,    
XD, Rimfire, ...)

>I'd replaced them all with Sun-2 units...

...which are dreadly slow and not supported under NetBSD.

James: Do you wanna trade? I have 4 Sun-2 SCSI controllers   
and i'd love to have 4 Sun-3 SCSI controllers...

>Yeah. I just spent an afternoon with some unpleasant termination
>issues.

Sometimes, my machines work ok only if i do not terminate
the SCSI bus at all!!! Silly, isn't it?

>SCSI allows for plenty of expansion, but it's pretty much plug-and-pray.

I've got a feeling for what works and what's going on...
And most SCSI problems have a simple solution: It's the cable!

Tschuess

Peter