Testing an HP 48GX RAM Card - Question


Hello all,

I have this old RAM card for my HP 48GX, but I don't really know the size of it or if it's working really correctly.

Is there a simple test I can run in the 48GX to give me the size of the RAM card and to test it?

Best regards,



first make sure the read/write protection switch is in the r/w position.

Then put it into port 1, eventually it'll give you an error,

like 'Invalid card data' or 'Battery P1 low'.

At this point just ignore these messages.

Then type 1 PINIT. After a while, when the the port init is over,

type 1 PVARS. This will return an empty list in level 2,

and the amount of free memory in level 1.

For more details, RTFM;-)




This brings up a related issue; Is there any way to test any/all available ports of a HP48GX Ramcard as blocks of RAM, similar to conventional RAM testing, that is, write/read each HW location in the RAM block?




this may also be a RTFM;-)

The HP-48 has some self-test capabilities,

amongst them some memory checks.

Of course you could write a small ML program

which reads/writes from/to each memory address,

but AFAIK the self-test does axactly that...

To enter the memory test, just press and hold the ON key,

press the forth menu key ('D'), then release both.

Three vertical lines will appear.

Now press the up-arrow key, and the main memory will be checked,

some pixel pattern will apear on the display.

After a while the display will show the starting address

and the size of the RAM.

To revert to normal operation, just press and hold ON,

then press the third menu key, then release both.




Thanks for the reply.

What I am referring to is not exactly what is built into the machine or in the manual; what I have in mind is something like specifying a particular address or range of addresses:

{13:00000 13:0ffff 5A}

Where the (proposed) utility would write/read a specific bit pattern (eg: 5A)to that range of adresses (eg: port 13, addresses 00000 to 0fff) and verify.

I do understand that each port does not have exactly 128 available. BTW, what are the unavailable locations used for?

Thanks again,


I do understand that each port does not have exactly 128
available. BTW, what are the unavailable locations used for?

PVARS shows all of my cards as having 131072 bytes per (empty)
port, which is exactly 128kB, (217 bytes). (I don't
have a 32kB card.)

That said, anything other than a library is stored in a port as a
"backup object", which is somewhat larger than the object it
contains. A "backup object" also contains its own name and a CRC
value, for example.

For example, a real number stored as a global variable named 'A'
takes 16 bytes of memory, but stored as a backup object named
:1:A, it takes 23.5 bytes.



It worked.

Thank you very much Raymond !


Does the card has any brand name or other markings on it? I
haven't heard of a RAM card the doesn't have the size clearly
marked, except for Oliver Klotz's cards.

As Raymond wrote, first set the switch to the r/w position. I
suggest putting the card in the 48GX's slot 2 instead of slot 1,
but indeed ignore any error message for now. Type in PINIT and
press ENTER (PINIT doesn't take any arguments). After the "busy"
annunciator turns off, press LeftShift LIBRARY (over the 2 key),
then press the PORTS menu key. You'll always see the :0: menu
label for port 0, and if a card is in slot 1, you'll also have a
:1: for port 1. With the card in slot 2, you should see at least
:2:. If you see more port labels, then each one is 128kB. If you
see only :2: for the card, then execute 2 PVARS to see whether
it's a 32kB card or a 128kB card.

32kB and 128kB cards can be used in either slot 1 or slot 2 of
either the 48SX or 48GX, but larger cards should be used only in the
48GX's slot 2. Exceptions to this are some TDS brand
multi-bank cards designed for the 48SX, and some of Oliver Klotz's
multi-bank cards with the current bank selected by switches on the
card, which work in either slot of either model.


Edited: 25 Feb 2006, 5:36 p.m.

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