[Info-vax] Assistance needed!! working RM05 drive and VAX needed for proje

[terry-...@glaver.org]

On Thursday, September 28, 2023 at 5:31:07 PM UTC-4, Johnny Billquist wrote:
> I've been reading the RM02/RM03 manuals, and I can't find any 
> documentation on any backplane jumper for such a purpose. There are 
> jumpers for drive type and serial number, but that's about it as far as 
> I can find. 

I assume you mean in the Massbus controller in the bottom of the drive.
The actual drive logic cage has not very many not very big not very bright
cards. As I recall, maybe 5" x 5". I modified a couple sets of drive cards
to change the upper cylinder limit. I was subcontracting data recovery
and they'd send me crashed-but-cleaned packs and tell me "don't go past
cylinder X" when doing the recovery.

I don't know why DEC didn't do Massbus disk strings the way they did
Massbus tape strings - you can't have multiple data transfers going at
the same time on the Massbus anyway, and the Massbus supported
per-drive things like "Seek Complete" already. I guess customers that
cared about over-paying for drives just bought the CDC versions and
3rd-party controllers.

I remember when Emulex came out with a new generation of SMD
controller - UD33, perhaps. I thought the biggest "win" on the new card
was getting rid of the high-speed processor logic in favor of dedicated
gate arrays. I asked my contact at Emulex (I was field testing) what
they thought the most important thing was. They said "controller-
resident diagnostics".

> By the way, it's kind of strange to talk about different "controllers". 
> Of course they are different. The PDP-10 have a very different massbus 
> controller compared to a PDP-11 or a VAX. But they all talk massbus, and 
> the devices on the massbus itself is sortof agnostic to the machine word 
> size. 

Massbus is weird. Somebody saw IBM 360 bus/tag cables and went
"This would be a good idea - how can we make it bizarrely different?"
Trivial example - the RP07 is logically an RM device, not RP. Surprised
a bunch of early customers who tried adding one to a string of RP06
drives.