11/44 memory question

[Don North]

Zane H. Healy wrote:
> At 10:04 PM -0600 11/4/06, Jay West wrote:
>> It would appear that the slots designated "MEMORY" in the 11/44 
>> (slots 9-12 in the *system* backplane) are actually "Extended Unibus" 
>> slots. My reading is that these slots allow 22 bits of memory 
>> addressing instead of 18.
>>
>> So, of they are still "unibus" slots, does that mean that if there is 
>> one board in slot 9, that slots 10-12 should have grant continuity 
>> cards (G727)?
>>
>> If they are unibus slots I would certainly think so, but they are 
>> designated for memory only... and I can't find any reference to using 
>> grant cards there for non-populated memory slots.
>
> I'm pretty sure you don't need grant cards, but my /44 is buried. The 
> /44 can use up to 4MB, and IIRC, I only have 1MB.  I needed the grant 
> cards, but in slots where options had been removed.
>
> It's just like you don't need any kind of grant card in the CPU slots 
> if you don't have the extended CPU options installed.

You don't need grant cards in the 11/44 backplane slots 9-12 since they 
are not SPC slots. The AB portion of the slot is 'extended unibus' EUB 
(adds address lines 18-21 for 22b addressing) but the CDEF sections are 
not SPC slots. If they are not used for memory they should be left 
empty; you can put a grant card (either type) in these unused slots -- 
it won't hurt anything, but it is not necessary. Empty memory slots 
cannot be used for UNIBUS SPC modules either.

Only the last two quad slots 13,14 CDEF in the 11/44 backplane are SPC 
and these require G727A/G7273 grant cards depending on whether the NPG 
wire has been removed.

The modules have the grant propagation lines intact because they could 
*theoretically* go in a MUD (modified unibus, 18b, with associated SPC 
section) or an EUB (22b) slot. These modules work in the 11/44 
(dedicated EUB memory) slots or the 11/24 (MUD/EUB/SPC slots) which need 
grant propagation.