Differences between PDP-11/83-84 M8190-AB/AC and AD/AE CPU cards

[Jerome H. Fine]

Does anyone know why DEC would have MSV11-JC boards for use ONLY
with a PDP-11/84 and the MSV11-JE boards which could be used with
BOTH the PDP-11/83 and the PDP-11/84?  It seems inconsistent.

 >Glen Slick wrote:

>>On Wed, Feb 4, 2015 at 7:09 PM, Jerome H. Fine <jhfinedp3k at compsys.to> wrote:
>  
>
>>Longer explanation:  The PMI memory used in the PDP-11/84 is sufficiently
>>different
>>from the PMI memory used in the PDP-11/83 that the magic smoke might be
>>released
>>if the incorrect PMI memory is used.  The MSV11-JB (1 MB) and MSV11-JC (2
>>MB)
>>are used in the PDP-11/84.  The MSV11-JD (1 MB) and the MSV11-JE (2 MB) are
>>used in the PDP-11/83.
>>
>The MSV11-JD and MSV11-JE are documented as being compatible with both
>the PDP-11/84 and Q-bus systems. The documented restriction is that
>the MSV11-JB and MSV11-JC are only compatible with PDP-11/84 systems
>and incompatible with Q-bus systems.
>
>http://www.bitsavers.org/pdf/dec/qbus/oemMicronotes.pdf
>
>uNote # 028
>MSV11-Q/M/J MEMORY COMPARISONS
>
>MSV11-J
>-------
>The MSV11-J has four versions, the MSV11-JB and the MSV11-JC which are
>used in the PDP-11/84 UNIBUS systems and the MSV11-JD and the MSV11-JE
>are used in either the MicroPDP-11/83 Q-bus systems, or the PDP-11/84
>UNIBUS systems. All four modules use ECC memory for error correction,
>as well as using 256K bit MOS RAM parts on either a half for fully
>populated quad size module.
>
>NOTE:
>-----
>NONE OF THE FOUR MSV11-J MODULES CAN BE PLACED IN A Q/Q BACKPLANE
>SLOT. IF THIS IS ATTEMPTED PERMANENT DAMAGE WILL BE DONE TO THE BOARDS
>AND TO THE SYSTEM.
>
>The MSV11-JB (M8637-BA) is a half populated quad size PMI memory
>module containing 1MB of memory. The second version of the MSV11-J is
>the MSV11-JC (M8637-CA), this is a fully populated MSV11-JB quad size
>PMI memory module containing 2MB of memory. These two module can not
>be used in a Q-bus system due to gate array incompatibilities, and can
>only be used in the PDP-11/84 systems which use the UNIBUS/PMI bus
>interface (KTJ11-A). The third version of the MSV11-J is the MSV11-JD
>(M8637-DA) which is a half populated quad size PMI memory module
>containing 1MB of memory. The last version of the MSV11-J is the
>MSV11-JE, (M8637-EA) which is a fully populated MSV11-JD quad size PMI
>memory module containing 2MB of memory. These last two modules can be
>used with either the MicroPDP-11/83 system which uses the Q-bus/PMI
>bus interface or the PDP-11/84 system which was mentioned above.
>
>Although the MSV11-JD and MSV11-JE are PMI memories they can be used
>in two other Q-bus configurations.
>(more details follow...)
>
THANK  YOU for the correction.  After 20 years, the memory becomes
a bit hazy.  Also, I have only the 2 boards which are both 2 MB, so there
must have been some confusion when I was told that a 1 MB and a 2 MB
board should not be combined.  It is good to know that is also not true.

Does anyone know why DEC would have both MSV11-JC boards for use
only with a PDP-11/84 and MSV11-JE boards which could be used with
both the PDP-11/83 and the PDP-11/84?

I have never worked much with Unibus systems and never with a PDP-11/84.
Also, thank you for confirming that these memory boards MUST  NOT be
used in a Q/Q backplane.

At one point, the MSV11-JE memory boards were equally priced with other
2 MB Qbus memory boards since most individuals thought they could be used
only as PMI memory.  I have no idea what the current prices are.

Jerome Fine