HP9845 service toolkit

[Tony Duell]

> 
> Tony replied to my comments about the HP BPC processor in the 9845:
> > I haev one of those. I don't think it's the same device -- exactly -- as
> > in a 9825, it appears to have more connections for a start. It is almost
> > certainly the same architecture, though.
> 
> The full processor is a three-chip hybrid.  But in some cases they
> use only the main processor chip.  That's what's in the 9872, and IIRC
> the I/O processor of the 9845.
> 
> Although the 9825 and 9835 use the three-chip hybrid, it may be a
> different version than the one that serves as the system CPU in the
> non-bitslice version of the 9845.

Perversely the I/O processor in my 9845 seems to have many more 
connections than the one in the 9825..... 

> 
> Regarding my comments on the bit-slice processor:
> > I have that. It's 3 PCBs with a little backplane on top to link them
> 
> Knowing how thorough you normally are with these things, I don't need
> to make any special requests about your reverse-engineering effort.
> But if at all possible, could you please dump the PROMs of that
> processor assembly?

Sometime, sure. They're soldered in IIRC which makes things a little more 
of a pain (but not impssible). The main ROMs are socketed, but are 
somewhat strange in that they contain address (?) latches. Well, put it 
this way. The buses of the 9845 processors are multiplexed address and 
data (like a 9825, not suprisingly), there are no address latches on the 
memory boards. 

-tony