Funny, someone just posted a thread about the HP-35s ROM.

I just had the occasion to use both my 48G and 48G+ the last couple of days. I have some constants I need stored on them and wanted to dig them out to put on my 50g. I noticed that the preloaded constants in the constants library of the 50g (naturally, I suppose) appear to be more up to date than those in the 48G machines' constants library.

I know that for most work, the differences appear generally in decimal places that aren't all that important. But still, it's nice to have the updated (and assumed more correct) numbers.

Is/was there a ROM update for the 48G series? I further suppose that any corrections to constants would appear in such an update. I did a quick poke around and did not even find an oblique reference to a 48G ROM or other kind of update.

There were a few different ROM revisions, although the ROM in those machines is not user-upgradeable. I'm assuming it's a mask ROM chip.

The comp.sys.hp48 FAQ has info about the different versions. Section 3 has ROM info.

http://www.faqs.org/faqs/hp/hp48-faq/part1/

Thank you, Dave. This does answer all my questions. Too bad it's not a flashable ROM. Even though I have the 49g+ and the 50g, I still use my 48g machines from time to time.