This month's online talk was by ex-Acorn and Pace RISC OS programmer Mike Stephens who worked at Acorn from 1994 for about 4 years and 2 years at Pace. He was heavily involved with StrongARM and Phoebe kernel.
Mike started with TI 59 programmable calculator and studied Physics at University. He had a string of home computers including an Acorn Atom, BBC Micro and RISC OS machines. Wrote his own Forth for Acorn Atom.
Joined Acorn in July 1994 as a software engineer. Worked on printer drivers and then RISC OS 3.6
Really enjoyed the culture at Acorn (and the cake shop round the corner). Concerns at the time over size of market. ARM was the wrong architecture at the time for desktop machines. Thumb instruction set wrong way for Acorn and bloated reference documentation.
Worked on verification for the ARM810. Had some powerful features like static branch prediction. Michael wrote a custom kernel. Took some work to get RISC OS running, using a logic analyser to debug issue with double LDM instructions. ARM810 overshadowed by StrongARM.
Survived the business reorganisations and change to ART. Desktop business was a cash cow to pay for diversification of Acorn. Only a budget for 2 people on StrongARM upgrade - Pete Fox and Michael. StrongARM was like "the tiger who came to tea".
Lots of challenges to make RISC OS run on StrongARM including the new caches. Big headache was altering task swapping for StrongARM. Solved with Application Memory blocks.
3.7 booted first time on the hardware but performance not great. Turned out due to not running at full speed (200mhz).
His next project was Phoebe's kernel. Also worked on the screen caching, lazy task swapping and speed-ups for Kernel.
Continued the RISC OS code improvements at Pace. Moved away from RISC OS after Pace. Back to playing with Forth these days on a Teensy 4.0
As always there was time for questions after the talk.
Many thanks to Michael for a very nice geeky talk with lots of low level details.
Next month will involve some people back in the pub and also online.