Patching vs. new code (was Re: Pascal not considered harmful)

Michael Holley swtpc6800 at
Tue Feb 24 00:21:11 CST 2015

In 1982 I was working at Data I/O, the PROM programmer company. Everything was written in assembler for the 6800. We had a cross assembler that ran on a PDP11, it was much faster than the Motorola EXORciser that used 8 inch floppy disks. We later updated to a VAX. On one project we had a firm code limit of 16K bytes, every week or so we would have to hand optimize our assembly language so we could keep adding the necessary features. We had about 20 bytes open when we were done.

I recall that the cross assembler was from a company named BSO.

Michael Holley

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at] On Behalf Of Ian S. King
Sent: Monday, February 23, 2015 9:17 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Patching vs. new code (was Re: Pascal not considered harmful)

My first (paid) programming job was in 6800 assembler, using the Motorola EXORCISER system.  It took hours (as in a major part of a day, longer than the work day) to reassemble the entire code base, so we would patch the program in the PROM programmer.  We would, of course, back port the changes in symbolic assembler to the source, and every few days just take the downtime hit to rebuild the code base.  Keep in mind that this was natively hosted on a 6800 system.

Another interesting tidbit: its simple filesystem did not segment files and reuse blocks, so you had to purge old versions of files, preferably before a dozen or so files were lined up after it.  In that case, it would tie up the system for way too long while an old file was purged and all the new files were packed into the recovered space, block by block.  It was barely a step above magtape.

One other note: there was a bug in certain mask sets that required a NOP before you could set the interrupt mask.  Since the ENTIRE memory/IO space was 64k bytes, every byte was sacred, every byte was great, and if a byte was wasted….

Ian S. King, MSIS, MSCS
Ph.D. Candidate
The Information School
University of Washington

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