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I ran across a reference to this in the Raspberry Pi forums. It might be of interest to anyone without a working Centronics printer.

Probably not too difficult for a hardware hacker to knock-up their own version.

If the chip is supplying 4 bits of data, would it be better to have two chips in parallel to supply 8 bits? Would the speed improvement in not having to repack the data be worth the cost of the extra chip?

Very good. I wish I could manage to be half as productive. One of the projects on my "long list" is to hook up an RPi to an exercise cycle and then interface it to Google Street View so that it is possible to do a virtual tour of London, Lake District, New York or anywhere. But then the ch...

A couple of small points on a quick review: Both the call and the return potentially change the RAM mapping. Now I admit that I did not specify that it should be preserved, but to be completely generic it should be. Your return code also potentially changes CRNTPG (0xFAD3). I am sure you won't find ...

A little puzzle to exercise your grey cells during these strange times :) One of the issues when writing code to go into an MTX ROM is calling a subroutine which happens to be in a different ROM. The standard MTX ROMs have a number of solutions for special cases, but the challenge here is to write a...

Should anybody be interested, attached is my disassembly of the SDX high memory. There are two major areas of unused memory at: EC5F - F5B0 F5EF - FA52 Much of this space is used by data structures for the NODE RING if that is installed. Adopting the principle of overwriting unused parts of the BDOS...

It is perhaps significant that back in the day I did not even know I had SDX ROM BASIC. Whenever I wanted BASIC with disk support I used FDXB. I think I even asked Memotech about it when I first got the drive, as I was not anticipating the extra cost of having to buy an 80 column monitor needed for ...

Looking at the ROM source there is a USER SYSCOPY command. This works by making a clean copy of the system tracks on a source disk, and then writing them back to the destination disk. Only issue is that the copy of the system tracks is placed at 0x8000, potentially overwriting any loaded program.

Thinking about this has raised a side question: Was there ever a manual for SDX BASIC? I never had one, and I don't see one on Dave's site. There is documentation for FDXB, and mostly you can just replace "DISC" by "USER". But FDXB relies upon CP/M to do disk formatting. So there...

It turns out that functions #25 and #28 are implemented in CP/M 2.2, see the source here . Presumably just not documented. I suppose what I am really questioning is why SDX makes use of the system tracks from the drive rather than just implementing everything in ROM. Was it really much quicker to sp...