9 Jan
2009
9 Jan
'09
8:35 p.m.
On Fri, Jan 9, 2009 at 9:24 AM, Henk Gooijen <henk.gooijen at hotmail.com> wrote:
I have seen plenty of older quad SPCs that do not use NPR have a
manually-added NPR jumper in case they are installed in a slot with
the wire removed. Newer SPCs frequently had that in copper.
I frequently get tripped up by this since where I learned about the
Unibus, we routinely removed *all* NPR jumpers and used our own
dual-height grant cards with NPR (and never used DEC G727
single-height INTR-only grants). It makes reconfiguration easy, until
you get a fresh backplane in a BA-11 and can't figure out why things
are hanging.
From: toby at coreware.co.uk
Subject: Re: PDP-11/05 returns to life
Finally, I have a choice of RX21 + RX02 or RX11 + RX01
... is there any reason not to go with the RX21/RX02 combo?
The only thing that pops into my mind is that RX211 uses
"DMA" and RX11 does not. That means that for the RX211, the
NPG chain must be cut (the wire between pins CA1-CB1) of
the slot that will have the RX211. For the RX11 that wire
must be present. If it is not, the system may hang.
That depends on whether the module connects these two pins.
Some SPC modules do this, some do not ... An other reason to go for RX02 is that with RX02 you
can also
read RX01 formatted floppies. The RX02 drive has internally
a switch to act as an RX01. It is ovbious that you can not
read RX02 formatted floppies with the RX01 drive.
And RX02 offers twice the capacity of RX01 ...
If I am wrong in any of this, please correct me :-)
Nope... all correct as far as I can see.
-ethan