5 Jan
2021
5 Jan
'21
4:36 a.m.
On 05/01/2021 11:47, Joshua Rice via cctalk wrote:
I?m not sure where i read it, but i?m pretty sure the
main ?brains? of the RQDX2 is a T-11 (PDP-11 FALCON) chip, and that does the negotiations
between disk and system. I don?t know if it?s the same for the RQDX3, but i?d suspect not,
as the incompatabilities between the 2 and 3 are probably due to a controller redesign.
Though i really am no expert when it comes to disk controllers, and barely qualify as an
amatuer with QBUS PDP-11?s in general!
The RQDX3 definitely uses a T-11 (the controller User Guide says so). I
don't know what the RQDX2 uses, although Wikipedia says that uses a T-11
too. They can use (at least) some of the same RDxx disks but the format
is incompatible between the two AFAICR. So you could move an RD53 (say)
from an RQDX2 to an RQDX3 (or vice versa) but you'd
have to reformat it
to use it: you could not read data written by an RQDX2 on an
RQDX3
(again, AFAICR).
I think that the (even older) RQDX1 was very similar to the RQDX2 but
had a design fault that meant it had to be the last module on the bus
(it failed to pass on the grant signal, I think).
Antonio
--
Antonio Carlini
antonio at acarlini.com