HP-85 Re: anyone in rochester?

From: Vassilis Prevelakis <vp_at_mcs.drexel.edu>
Date: Fri Aug 29 18:05:14 2003

Joe <rigdonj_at_cfl.rr.com> wrote:
> > BTW I have finally managed to get a 98155A keyboard for my 9915's
> Congradulations! Where did you find it? It took me years to find one.

On eBay, for $35

as you can see I used the Buy Now option, and not a moment too soon,
the seller told me that he had higher offers from others that came

> GREAT! I've been looking for those for years. The only one that I have
>is for networking the 9915s.
Do you mean the system for making backup tapes with a bunch of
9915s connected via HP-IB? Do you have the s/w for that pac?


"Jay West" <jwest_at_classiccmp.org> wrote:
> What about the 9122?
you'll need the EMS ROM for that one.

> I'm hoping it would work with the 9122, which is what I want to get for my
> 1631D. The only reason I'm hunting for 9122 instead of 9121, is I thought
> the floppy disks for the 9122 might be easier to find (they DO use different
> media right?)
The difference between the 9121 and the 9122 is that the former is single
sided and the latter double. Apart from that they both use the DOUBLE
density format which is different from the QUAD density PC floppies.
So while you gain in capacity with the 9122, you still need to find these

BTW note that while the 9121 is very reliable, there are quite a few
9122s with damaged heads. This has to do with the disk loading mechanism
that gets stuck with age and if the user forces the diskette in, it
hits one of the read/write heads.

> Thanks for the tip!! I don't have too many old DECtapes, but when you say
> old 40mb PC tape drive tapes, are you talking QIC-80 tapes? I have tons of
> those. If not, exactly what tape do I go buy?

CAREFULL! The HP-85 tapes (and the DECtapes) are NOT the same as the
QIC-80 tapes. They look the same, to the extent that I was trying to
insert one and getting annoyied when it wouldn't go in.

> I saw note of that on your website. That would be soooooooo so nice to have
> n ROM emulator. Humm there can't be THAT much to the electronics inside the
> 2929A. Anyone have one they'll let me take apart and build a copy of?

Actually its not that complex. If you look at
you will see that most of the chips deal with address decoding. You can
replace most if not all with a microcontroller (e.g. PIC).

BUT, (there has to be a but, otherwise, I would have already pointed
you to a page that tells you how to build one :-) The HP-85 bus is
not TTL. I think the logic true is +6V and the clocks are like +12V.
So you need more than a PIC. Like I said, its in my TODO list.

Having said that, relocating the ROM executable may actually be easier.
But (there's that word, again) when I tried to look at the CPU
architecture, I freaked out. What the **** were they doing back then.
This CPU is totally wierd, so understanding what is going on with
that thing will take some effort.

Anybody who knows/remembers HP-85 assembly? :-)

Received on Fri Aug 29 2003 - 18:05:14 BST

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