HP48 FAQ Section 3: Questions about ROM versions

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3.1 What does the SX/GX have that the S/G doesn't?


The HP48 S is the same as the HP48 SX except that the HP48 S does not have the two expansion slots of the HP48 SX. This means that the HP48 S cannot be expanded and can only access 32K of memory, versus 288K for the HP48 SX (two 128K RAM cards). (Actually, there are third-party RAM cards that contain 256K or 512K on a single card -- this memory is accessed via a bank-switching mechanism.)


The HP48 G is the same as the GX except for two differences. The GX has the 2 expansion ports, and also has 128K RAM built in, whereas the G only has 32K.

If you plan on heavily using your calculator, you will probably find that 32K is not enough memory. In fact, some of the best HP48 Programs will not even fit in this memory!

3.2 What is the difference between the HP48 G/GX and the HP48 S/SX?

The HP48 G/GX calculators are, basically, slightly faster (by 40%) versions of the HP48 S and HP48 SX calculators, with more features, such as 3D-plotting and a new forms-based interface. Much of the HP Solve Equation Library card is now built-in. See Appendix B-1 for a detailed list of GX features.

Note, however, that the HP48 G/GX is different from the HP48 S/SX in a number of significant areas:

  1. The HP48 GX comes with 128KB RAM, as opposed to 32KB RAM in the HP48 SX. The HP48 G still has 32KB RAM, however. The HP48 G/GX also has twice the ROM (512K), compared the HP48 S/SX (256K).
  2. Much of the HP48 G/GX internals have changed, compared with the HP48 S/SX. Unfortunately, this means that many programs written in assembly language or System RPL won't work on the HP48 G/GX. This is especially true of any program that tried to access the display memory directly.
  3. The HP48 G/GX CPU runs at 4 MHz, instead of the 2 MHz used with the HP48 S/SX CPUs. However, due to various overheads (memory bank switching, etc.), the speed increase between the S/SX and G/GX is less than 2 times. G/GX throughput is approximately 40% faster.
  4. Slot 2 of the HP48 GX can access up to 32 ports (ports 2-33) by bank switching. Each port is 128KB, for a maximum total of 4 MB in slot 2.

3.3 What is the HP48 G+?

The HP48 G+ was announced 30 March 1998. It is essentially a HP48 G with more memory - it has 128K of memory instead of 32K. All G+ machines have revision R ROMs.

There is no change to other aspects of the calculator model offerings. Specifically, it looks like HP has added to the HP48 family without withdrawing anything. The G, G+, and GX will all continue to be sold.

The press release for the HP48 G+ is at: http://www.hp.com/pressrel/mar98/30mar98.htm

3.4 How can I tell what ROM revision I have?


Type the command "VERSION". Note that this command is not part of any key or menu, and so you must spell it out.

Type #30794h SYSEVAL. It returns a string, "HPHP48-x", where x is your ROM revision. This works for both SX and GX.


  1. Turn the calculator on (press ON and then release).
  2. Press ON again, and hold it down.
  3. While holding down the ON key, press and hold down the "D" key (the fourth white key in the top row).
  4. While holding down the "D" key, release the ON key.
  5. Release the "D" key. The display should be blank, with the exception of three vertical lines (one down the centre, and one down each of the right and left sides).
  6. Press the backspace key (it says DROP and CLR over it). A meaningless string of digits should appear in the top line of the display (mine says "705D9:1B8DA178E5A111B6" -- yours may be different).
  7. Press and hold down the EVAL key. It should say something like the following, where the ? is an uppercase letter indicating the ROM version:
    Version HP48-?
    Copyright HP 1989
  8. Release the EVAL key. Hold down ON and hit "C" (the third white key in the top row. This is a general reset operation that returns the calculator to normal from the diagnostic stuff (which is where ON-D puts you).

3.5 What bugs exist in the various versions of the HP48?

Rom: A

Roms: A-C

Roms: A-D

Roms: A-E

Roms: E, J

Rom: K

Roms: K, L, M, P

Rom: L

Roms: L, M

Rom: M

Roms: L, M, P

Roms: L, M, P, R

Roms: M, P, R

Roms: M, P

Rom: P

Roms: A-R

Roms: K-R

3.6 What is new with the revision "J" ROM? (S/SX)

The revision J ROM has a faster equation writer, as well as some bug fixes. Scrolling of graphics is also faster.

One "problem" is that the revision J ROM changed some undocumented ROM entry points, which broke those programs that used them. If you have a Rev J ROM, you will not be able to run some old programs.

3.7 What happened to ROM revisions G, H, I, O, and Q?

These versions either were never released to the public, or were skipped over.

I have received confirmation of the existence of a HP48 S with ROM revision F. So it appears revision F was in fact released to the public, although very few must have made before revision J came out.

3.8 Can I upgrade my HP48 S/SX?

When the G/GX first came out, HP had a trade in program. This is no longer in operation. The only option remaining is to try to sell your S/SX privately.

3.9 Can I upgrade my buggy GX to the latest ROM revision?

As far as I know, not any more. They had a program a in early '94, but it is over now. Contact the following for more info:

Hewlett-Packard Corporation
Calculator Support
1000 NE Circle Blvd
Corvallis, OR 97330

Phone: (970)-392-1001

3.10 What's the latest ROM version?

3.11 Why would I buy a S/SX rather than a G/GX?

Here's the top reasons to buy a S/SX instead of a G/GX (Thanks to all who contributed):

  1. May be slightly cheaper, having only 32K RAM.
  2. It isn't THAT outdated.
  3. So what if it's a little slower?
  4. You didn't need all those useless equations, graphics capabilities, and math and science functions anyways!
  5. If you break it, you're out of less money!
  6. You like seeing how much you can fit into 32K RAM.
  7. You like slow file transfers, using Kermit instead of X-Modem.
  8. You want to be able to use all those lists of SYSEVALs for the SX.
  9. You like having only 3 ports available max. 33 is ridiculous!
  10. Since it doesn't have a built in equations library it is less likely to be banned on tests.
  11. Only wimps need GUI's, dialog boxes, and choose lists.

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