Jim Bender wrote:

> 
> So the upshot is, that while both ends of the BUS (host controller and drive
> circuitry) can move data at a pretty good clip, the physical drives DEC
> attached to it were not up to the task.   I have never seen good transfer
> rates from ANY RAxx series drive on ANY DEC CPU under ANY OS.
> 

No, that's just not correct. RD series drives like RD53/54 were just
rebadged industry standard mfm drives with access times of around 28mS.
I've used rd53 and RD54's in pc's and they run just fine. The RD54 in
particulr, probably represented the state of the art in drive design at
the time.

The real problem was the controller - RQDX series controllers were so
slow one sometime wondered if the damn thing would ever return a block
to the os at all...
They could have made those controllers much faster, but I suspect not so
for marketing reasons ;-(...

The UDA50 was much better - have some benchmark figures for various disk
controllers, uda50 included, running on 4.3 bsd in which the uda50
showed up quite well against stuff like system industries smd
controllers - istr, it was a funded research project. Will see if I can
dig out the article... 

> 
> No Massbuss adapter for BI machines...  at least not the ones we were
> running.     :-(
>

Just like the RLV12 and RLxx series drives - non intelligent, simple
interface that subjectively blew the pants off RQDX.. controller drive
combinations, even with the slow access time of the RLxx drives.

Rgrds,

Chris