21 Sep
2015
21 Sep
'15
6:29 p.m.
On 2015-09-21 19:20, Paul Koning wrote:
DECs various decisions related to the PRO are probably a mystery to all.
On Sep 21, 2015, at 12:47 PM, Johnny Billquist
<bqt at update.uu.se> wrote:
...
Way more primitive is a polite way of putting it. Just like all other PRO controllers
DEC ever built, it uses programmed I/O. The curious thing is that the PRO bus actually
appears to support DMA, but it was never used, not even for the hard drive or network
interface. All those devices do I/O to on-card memory, and then the driver has to move it
to/from host memory. I suppose you could on a Pro, since that had its
own particularly disgusting junk controller. But I haven't seen RX50 formatting
there. My impression was that they came factory formatted, with the DEC-specific 10
sector per track format.
Ugh! The PRO controller probably was weird enough to not allow you, even though as far as
I understand, it was also way more primitive than MSCP. I haven't tried this, but the PRO technical manual
(on Bitsavers) shows that (a) there is no way to do formatting, but (b) you can configure
the controller to accept, for reading but not writing, various non-RX50 formats.
Interesting. I haven't even tried digging that deep into the
documentation. If I ever found the drivers for the hardisk and floppy
for P/OS I could possibly consider trying to build something more purely
RSX-like, but I doubt that will happen.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol