30 Sep
2023
30 Sep
'23
10:11 p.m.
On Sep 30, 2023, at 12:47 PM, Johnny Billquist
<bqt(a)softjar.se> wrote:
On 2023-09-30 17:59, Robert Armstrong wrote:
Afraid it's going to be more complicated than that.
DEC in all it's wisdom decided to make the Pro hardware not really that PDP-11
compatible. So any OS that you want to run on the Pro will need to be rehacked in order to
make it possible.
Any "normal" RSX will not run on the Pro out of the box. Neither will any other
OS.
"Not really... compatible" is understating things. In fact, it is utterly
unrelated to a real PDP-11 except in the CPU. Everything involved in I/O, from the bus to
the peripheral devices to the interrupt system, are thoroughly different and in many cases
quite messed up. Part of the problem is that the Pro-350 uses a pile of Intel chips,
perhaps in an attempt to reduce cost, and as usual for Intel those chips have many bad
design features. The interrupt controllers are particularly nasty.
It doesn't help that all the I/O devices (except for CNA) are programmed I/O even
though I think the bus supports DMA. Doing hard drive I/O one word at a time is ugly,
though it turns out the controller is so pathetically slow that the CPU isn't the
limitation even with that horrid design. (I found this out when I tried to reduce the
interleave on the Pro-380. No go: the standard interleave is the best possible both for
the Pro-350 with its F-11 and the -380 with the significantly faster J-11.)
paul
Thomas
DeBellis <tommytimesharing(a)gmail.com> wrote:
Until we started using it an early version on a daily basis...
I always kind
of liked the PRO, although the "native" OS, P/OS, is not a feature. I actually
have a 380 with an NI out in the garage; I should get it out and try to install MicroRSX
on it instead. Does anybody know if there's a copy of the version with the PRO
drivers somewhere?