PDP-11 Memory

[Jerry Weiss]

On 1/12/19 11:39 AM, Bill Gunshannon via cctalk wrote:
> On 1/12/19 12:29 PM, Pete Turnbull via cctalk wrote:
>> On 12/01/2019 01:24, Zane Healy via cctalk wrote:
>>
>>> I’m pretty sure you could get the /23+, /53, /73, /83, and /93 in
>>> either a BA23 or a BA123.  I have an actual badged BA23 pedestal for
>>> my /23+.
>> I'm fairly certain all microPDP-11/23+ systems were only sold in BA23
>> boxes, and I think microPDP-11/73 and the later, cheaper, cut-down 11/53
>> were as well.  But almost all the 11/83 systems I've ever seen were in
>> BA123 boxes, though they did sell some in BA23 pedestals - I've got one.
>>
> One confusing part of this.  Everything I have read today
> seems to say that the only difference between the 11/73
> and the 11/83 in a MicroPDP-11 was the memory used.
> QBUS = 11/73
> PMI = 11/83
>
I use this guide in general - 
http://web.frainresearch.org:8080/projects/pdp-11/dcj11.php to 
understand the key differences in DEC DCJ11 implementations. You can see 
how the clock speed, caching and memory type drove differences in 
performance and marketing labels.

The 11/83 (M8190-AD or AE) with Non-PMI memory is just a slow 11/83 in 
my view. I know RT11 did report it as an 11/73.   It could be that from 
a software perspective, RT11 might not be possible to determine the 
actual module in use.

Does the 2MB 11/93 not work with and extra 2Mb of QBUS Non-PMI memory?  
I would have thought the upper 2MB would still be addressable, if for 
nothing else than for compatibility memory mapped display controllers 
and such.

    Jerry