Attention - Your MPF-IP BASIC ROM IMAGE from the Internet is bad!

A project log for Exploring the Microprofessor

A journey to explore and better understand the Multitech Microprofessor machines in my retro computer collection

Michael WesselMichael Wessel 01/19/2022 at 19:264 Comments

Preparing for my demo video of the MPF-IP BASIC, another Microprofessor MPF-IP enthusiast I was chatting with on another forum just complained that his BASIC wouldn't print properly beyond 18 characters, and that certain BASIC statements documented in the manual don't work (SON, SOFF).

I said, what do you mean? My BASIC just works fine, no issues with the printer, and SON / SOFF work flawlessly!

He then pointed me to the BASIC ROM image he was using:

I grabbed it and burned an EPROM, and indeed - this version must be a prior version and has these issues! For printouts, you'll have to limit yourself to 18 characters per line, else your printout looks as follows:

Now, my original BASIC ROM is indeed working fine, has SON / SOFF, and printing works fine beyond 18 characters: 

Seems the MPF-IP BASIC got a major update. There is no obvious version number encoded in the ROM image (at least not in ASCII).

Comparing the ROMs a bit, I see that they even omitted the READY prompt in order to accommodate the patches and SON & SOFF... the new version goes to 0x1ff8, whereas the "buggy" version has 0x1ff3 as last address. So a few bytes more. They really used almost all of the 8 KBs in the 2764!


Michael Wessel wrote 01/20/2022 at 00:39 point

Indeed! So much that the removed the "READY" prompt in "my" version - probably to accommodate SON / SOFF and the fixes (upgrades) to the printer routine.

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Ken Yap wrote 01/19/2022 at 22:43 point

Would it be possible to compare the blank bytes at the end of the ROM image? Since updates tend to use more code space, one might expect a newer version to have less free space.

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Michael Wessel wrote 01/20/2022 at 00:32 point

Yes, they are different for sure... the "bad" BASIC ROM ends at 0x1ff3, where the "good" one (mine) ends at 0x1ff8 - so a few bytes more. Both ROMs use the 8 KBs in the 2764 almost fully.

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Ken Yap wrote 01/20/2022 at 00:36 point

Wow they must have worked hard to squeeze it all in.

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