Some fun with CP/M 2.2

Announcements about the Altair 8800 Clone including software and hardware updates.

Some fun with CP/M 2.2

Postby AltairClone » August 9th, 2014, 9:43 pm

The most common (if not the only) version of CP/M 2.2 for the Altair that can still be found among vintage computing hobbyists is the “Burcon” version released in 1980. Burcon was a computer store in the Houston area that sold Altair computers. Burcon CP/M is on the disk images in the CP/M 2.2 folder on the Altair Clone support page.

The Burcon version of CP/M is common today, not because of widespread distribution in the early 1980's, but because most everyone who has presently has a copy of CP/M 2.2 for the Altair obtained it directly, or indirectly, from the same computer hobbyist within the last decade or so. Lifeboat Associates, a large software distributor at the time, released CP/M 1.41 for the Altair in 1979 and released CP/M 2.2 for the Altair in 1981. Based on the people who originally had copies of Burcon CP/M, it is likely that Lifeboat CP/M 2.2 is a re-branding of Burcon CP/M 2.2, or just a minor revision. While copies of Lifeboat CP/M 1.41 are not hard to find today, I have yet to see a copy of Lifeboat CP/M 2.2. If anyone runs across it, I'd love the chance to archive it!

If you've been using CP/M 2.2 on the Altair Clone, you've been running the Burcon version of CP/M 2.2. The disk layout used in Burcon CP/M duplicates the disk layout used in Lifeboat CP/M 1.41. This means the disks, at least in terms of copying files, are interchangeable between the two versions of CP/M. However, the disk layout - specifically the sector skew - was not chosen wisely for optimum performance of most CP/M applications.

After 34 years, I decided it was time to fix what was wrong with Burcon CP/M 2.2 and give the Altair a kick in the pants! CP/M version 2.2b is an update of Burcon CP/M 2.2 that provides substantial speed improvements along with a couple additional features:

  • Compared to Burcon CP/M, version 2.2b loads CP/M programs in less than half the time. Any program with substantial disk I/O will run 20%-50% faster. By using track buffering to optimize disk access, no changes were required to the sector skew versus Burcon CP/M disks, so version 2.2b can interchangeably read and write Burcon (and Lifeboat CP/M 1.41) disks.

  • Version 2.2b provides a full implementation of CP/M’s IOBYTE feature which allows re-direction of logical CP/M devices to a variety of physical devices. This allows use of serial ports in addition to just the first 2SIO port and allows programs like Kermit, which requires IOBYTE, to run properly.

  • To better support a Teletype as the console, version 2.2b automatically transmits a null after C/R when it detects a Teleltype as the console during cold boot.

It's a fun exercise to spend some time using Burcon CP/M 2.2, then switch to the updated version 2.2b and perform similar operations. The speed improvement is immediately noticeable. This speed improvement has nothing to do with modern hardware or the Clone - version 2.2b gives the exact same performance boost to a real Altair and floppy drive.

See the CP/M 2.2B folder in the CP/M 2.2 folder on the support page for more information. Feel free to contact me with any questions!

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