CPM 2.2 ul compatibility

We've been getting a lot of letters from Kaypro owners who have more than one Kaypro. The problem they've encountered is the inability to run some software from new machines on an older Kaypro model.

This has been especially prevalent with software that came with the newest Kaypro models that sign on CP/M 2.2ul. The BIOS (Basic Input/Output System) for this revision of CP/M 2.2 is radically different from prior Kaypro revisions. What Kaypro has done is come up with a BIOS where the ROM-resident portion is the same for all CP/M Kaypros. Part of this BIOS, and all prior ones, is a translation table to alter the codes sent by the cursor and keypad keys into the ASCII values that Kaypro wants those keys to have. The location of this translation table is the cause of the entire problem.

The programs that give trouble when run on older machines are the bundled versions of WordStar, DataStar, and any bundled program making use of cursor keys.

WordStar's Patch

Using WordStar as an example, the following sequence of events takes place: Kaypro's WordStar has been patched to go into the translation table in the BIOS. It then saves the ASCII code produced by each cursor key and replaces each ASCII code with the value that it prefers (^E, ^X, ^S, and ^D). That way the cursor keys now send the cursor movement codes that WordStar wants, rather than ^H, ^L, ^J, and ^K. When you exit WordStar, the cursor keys are restored to their original codes.

The problem is that the BIOS for CP/M 2.2ul has the translation table in an entirely different location than in prior revisions. So, when you try to run a WordStar that came with 2.2ul, it overwrites a totally different portion of the BIOS than was intended. At that point the program appears to go completely nuts. When you exit from WordStar, the portion of the BIOS that was overwritten is restored to its original state and everything works properly again.

This situation exists only on bundled software that uses the cursor keys. But some users, as well as a few dealers, have jumped to the conclusion that no software written for CP/M 2.2ul Kaypros will run on older machines. Wrong! New MicroPro software, for CP/M 2.2ul, won't run properly on older Kaypros because of the cursor key patch. The only other programs that aren't portable are machine specific utilities like DUTIL or CONFIG. The only other exceptions are programs that use video attributes available on '84 series Kaypros but not on the '83 series. There has never been any inherent incompatibility among different models of CP/M Kaypros.
(Profiles, December 1985)