Old HP48SX resurection and upgrade

[rprosperi]

(02-19-2019 05:14 PM)manjo Wrote:  Interesting thing is that, in some places ports are refered to as Port-0 and Port-1, on other places PORT1 and PORT2...go figure...
It seams .. I was just lucky...

Port-0 is not the same as Port-1. Port-0 is a section of Main RAM that has been set aside for storing Libraries. So if you STO a library file using :0 as the storage location, a portion of Main RAM is allocated (and removed from Main RAM) to store that object.

So on the SX there really are 3 areas for storing libraries, Port-0, Port-1 and Port-2. On the SX, Port-1 and Port-2 can only hold 128KB HP RAM cards, while on the GX, Port-2 can hold larger cards, accessed in 128KB virtual 'Ports' (i.e. Port-3, Port-4... Port-33 for a 4MB card); internally, these virtual ports are transparently mapped into the same address space as Port-2 via a bank-switching scheme, collectively called 'Covered Ports', but addressed by the user as Port-3, Port-4, etc.

There also were 256KB and 512KB RAM cards for the SX made by Tripod Data Systems, which were similar to the GX covered ports except the user had to manually use commands to select which port was active (only one at at a time could be accessed, but you could program card selection to make it somewhat automatic); these were always addressed by the physical port number that the card is in. Although these cards do not say 48SX on the label, they can be identified by the combination of RAM size (256 or 512) and copyright date before the GX was introduced in 1993. All the cards of this type I've seen have copyright date of 1991, though I imagine '90 and '92 are feasible as well).