HP21MX booster board?

[Jay West]

Bob wrote...
> The board I'm describing here is just about half the size of the CPU 
> board.
> Despite its name, it does not hold microcode ROM's.  It does have a series
> of 74S181 ALU chips and other logic that expands the data paths and ALU
> of the main CPU.
Yup, same board I've got here, including about five 181's.

> In an E-series machine, this board and its additional microcode can be 
> removed to return the CPU to a 'stock' configuration.
I figured the microcode and booster board needed to be removed (as well as 
the custom loader ROMS) ;) I wasn't sure if there was any customizations 
directly to the mainboard. I'll power this one up and run it through a full 
diagnostic set to see if it works. If so, nice to have a spare for my M 
series machines.

> I'm not sure how the
> extra bits of the booster board get mapped into the mircoengine of the M 
> series.
The M series booster board connects to the M series mainboard via the front 
panel connector (J1). That part I remember for sure. There was also a board 
in the I/O cage marked "05443-60031 MOIB interface". I THINK the ribbon 
cable went from this board went to a board in the front area, perhaps the 
booster board. I didn't pay that close of attention figuring I'd not be 
using it. There was also an odd HP-IB board. 15420A. This went in the I/O 
card cage and had an HP-IB connector on the back that protruded through the 
case. I'm asuming it wouldn't be usable for a "normal" HP-IB interface.

> In any case, the E-series version of this board is fairly common, I 
> probably
> have 4 or 5 extras, as well as a complete CPU with all the cables and 
> ROM's.
Ok, I'll probably strip the 15420A, MOIB interface, and MOIB board for 
parts. At the very least I want the 1820-0956 chips!

Jay