19 Feb
2022
19 Feb
'22
1:40 p.m.
On Feb 19, 2022, at 10:51 AM, Noel Chiappa via cctalk
<cctalk at classiccmp.org> wrote:
The -11/34 (not the /34A) has something unusual for grant timeouts, but I
forget the details. I'll look it up.
On Feb 19, 2022, at 12:11 PM, Fritz Mueller <fritzm
at fritzm.org> wrote:
I just did an 11/34 restoration last year, so this is fresh in mind ? I think you are
thinking of the M9302, Noel: a far-side terminator card with integrated SACK turnaround?
A few additional details, in case it is helpful:
IIRC, the 11/34 doesn?t have SACK timeout implemented in the CPU cards (the /34A did add
this, however.) So without an M9302 on the far end of the bus, the CPU could hang in a
situation with an unacknowledged grant (which I think would be somewhat rare, but
possible). I believe it is possible to boot an 11/34 at least as far as a ROM boot
monitor with a non-SACK (M930 or such) terminator on the far side.
An 11/34 with a M9302 SACK terminator _will_ hang, though, with a broken grant chain ? the
floating grant will trigger the M9302 to continuously assert SACK locking the bus.
?Better? CPUs, which used SACK timeout instead of turn-around, were more robust this way.
Incidentally, I think the 11/34 was contemporaneous with, and usually found with, the
slightly earlier M9301 ROM terminator on the near side, rather than the later M9312,
though both should work fine.
cheers,
?FritzM.