1 Oct
2023
1 Oct
'23
1:04 a.m.
On 2023-09-30 22:07, Paul Koning wrote:
I heard a slightly different story that the support chip just could not
run at a higher frequency. Which seems more plausible.
Becuase I can't believe that the support chip really have to run at a
multiple of 10MHz. So if the J11 runs at 18, if something else is
expected to run on half of that, let it run on 9 then. Or else I don't
understand at all what the limitation would be. But either way, it's the
way it is. Not going to change.
Even worse, though, is that P/OS will not use the separate I/D space, or
supervisor mode which is avaibale in M+, because P/OS also needs to be
able to run on the F-11 which do not have this.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
On Sep 30, 2023, at 10:49 AM, Robert Armstrong
<bob(a)jfcl.com> wrote:
Yes, a J-11 but clocked at 10 MHz. Allegedly it is because the J-11 was originally
specified to go up to 20 MHz, and the Pro system control chip assumed that and used a
synchronous design for the other clocks. When the J-11 dropped down to 18 MHz, the design
couldn't deal with such non-integer ratios and had to drop back all the way to 10
MHz.
I have no idea of the merit of that story but it was a rumor I heard around the time that
machine arrived. Johnny Billquist <bqt(a)softjar.se> wrote:
... they locked themselves into slow hardware
and only use what the F11 could provide.
Didn't the PRO-380 have a J-11?
Although as I remember the J-11 CPU in the PRO was limited to a pretty
slow clock speed because of other system limitations.