HP-75 RAM expansion?

[Sylvain Cote]

(10-12-2016 08:59 AM)Martin Hepperle Wrote:  some weeks ago I read somewhere among my CD/DVD files an old publication about a home made RAM upgrade for the HP-75 using two RAM chips.
These were to be soldered piggyback on existing RAM chips and the corresponding Chip Select lines routed to the PCB.
The article also explained that one has to mill out part of the case down to the metal cover plate to provide enough space.
Now I cannot remember where I read this. I believe that this was in some conference proceedings, but I cannot find them anymore.

I have looked at all the 1980's proceeding and found nothing on this, but I will have another look just in case I have missed it.

(10-13-2016 10:38 AM)Michael Fehlhammer Wrote:  I thought 24 kB is the maximum RAM an HP 75 can address due to limitations of the address space.

You are correct.

(10-13-2016 10:38 AM)Michael Fehlhammer Wrote:  Could more RAM be managed by the operating system (without patching it)?

Not to my knowledge.

(10-13-2016 10:38 AM)Michael Fehlhammer Wrote:  Wouldn't a complex bank switching mechanism have to be implemented?

Yep! and you also have to manage the file system and the runtime space before doing the BS.
IMHO this should be part of the OS, it may be possible to do it in a LEX file but the person doing it must really understand how the OS works.

I am following this thread to see where it goes ...

Sylvain