Need help with dead 11/23+, FIXED :)

Pete Turnbull pete at
Tue Oct 14 02:37:09 CDT 2008

On 14/10/2008 04:41, tiggerlasv at wrote:
>> Are these the most recent versions of 11/23+ proms?? I have an 11/23+
>> that I was going to update.? Are both of these versions compatible
>> with all M8189 boards and would the M8189-BG version be the better
>> image to use?
> Got me on that one.?? All of the boards I've ever owned
> have had proms -183 and -184.?? I was thinking those
> boards were -BH, but I could be mistaken; they might
> have been -BF . . .

The exact same board (M8189) is used for two different machines, 
PDP-11/23plus and microPDP-11, the difference being the ROMs (and the 
chassis) used.  It's the ROMs (alone) that that make the difference to 
the suffix, and therefore whether the board is designated an 11/23plus 
CPU or a microPDP-11/23 CPU.

23-339E2 and 23-340E2 are 2k x 8 and make an PDP-11/23plus (-BA)
23-158E4 and 23-159E4 are 8k x 8 and make a microPDP11/23 (early -BE)
23-238E4 and 23-239E4 are 8k x 8 and make a microPDP11/23 (later -BE)
23-183E4 and 23-184E4 are 8k x 8 and make a microPDP11/23 (-BF)
23-380E4 and 23-381E4 are 8k x 8 and make a microPDP11/23 (-BG)
23-453E4 and 23-454E4 are 8k x 8 and make a microPDP11/23 (-BJ)

When DEC brought out the microPDP-11 series they also brought out a 
range of I/O and storage devices to go with them; the difference between 
the "plus" and "micro" series bootstraps is partly support for those 
devices, but they also are more interactive.  So there was only one set 
of ROMs released for the PDP-11/23plus but several sets for the 
microPDP-11/23.  The later the version, the more MSCP boot devices are 
supported, and you're supposed to upgrade the ROMs in a KDF11 to match 
those in the RQDX1 or RQDX2 controller *and* vice-versa, and you should 
definitely use -BF or later for RQDX3.  Version -BG (called -BH in some 
places, it's the same ROM set and same code) introduced TK50 boot 
support, and -BJ refined that to make it more reliable.

Pete						Peter Turnbull
						Network Manager
						University of York

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