Re: Rockwell instruction extension
Posted: Mon Nov 10, 2025 8:34 pm
litwr wrote:
It would be interesting to know if this extension could help existing computers from the '80s. I can think of only one system that could benefit: the Commodore +4. The Commodore +4 uses a port at 1 for communicating with serial devices, such as disk drives, so the extension could provide a faster method of working with this port and potentially speed up the turbo loader.
Does anyone have any similar examples?
Does anyone have any similar examples?
In the early 1990s, I did extensive development work on a terminal server powered by the 65C02. Despite lots of bit-twiddling going on, I didn’t find the Rockwell extensions to be useful. The primary reason was the I/O hardware (an octal UART and a PIA) was not mapped into page zero, rendering the extensions useless in that application. I did, however, make extensive use of TRB and TSB, which tend to be more flexible—they have absolute as well as zero page addressing modes, and it’s possible to test and set/clear multiple bits in one atomic operation. In my 65C816 code, TRB and TSB see extensive application, especially in manipulating ephemeral workspace on the stack.