The original PATB wasn't for CP/M, it was intended for a 2K ROM or loading into RAM from paper tape via TTY. There were several versions ported to CP/M, though. The original was written with only two I/O routines, OUTC & CHKIO, character-oriented routines for talking to a TTY via OUT 01 and INP 00/INP 01 on the 8080. There was no support for a filesystem. The first addendum to PATB published was a routine that allowed the TTY to be switched off and a Processor Technology VDM board could be used instead.
PATB appeared in DDJ's May 1976 issue, which I recall appearing in early June. The VDM addition came in the June/July issue, which I recall appearing about the 4th of July. If the original source isn't on the web, let me know. I've scanned it and the addendum from my old DDJs and put it in a PDF, though it's rather large. I'm better at such things now, so if it's not available elsewhere I'll try to post it in a reasonably-sized PDF. It really does make good reading.