Faster than hub
K2
Posts: 693
in Propeller 1
A million years later, a sort-of accidental capability of P1 is still the salvation of many of my projects. Today's pinch goes something like this: A cog has only 25 instructions (1.25 uS) with which to fetch a five-bit value from another cog, do a local table look-up, a quick calculation, clock the results out serially, and finish a waitcnt (for sync purposes).
There is absolutely no time to wait for a variable length rdlong to execute. Grabbing the 5-bit word from port A, written there by another cog, is the only way forward. I LOVE that hack.
I was a stinker campaigning for something like that on P2, which Chip accommodated by letting neighboring LUTs talk. I hope I'm not the only one that has benefited from its inclusion.
Comments
I always wanted port B implemented for much the same reason, even if it had no actual pins connected. If the P1 is ever "re-spun" I hope Parallax adds that.
Ross.
I believe Chip has said many times that the Prop1 would've been revised if it was possible. But the tools used were obsolete even back then. It was always a one-off design.
The only thing stopping the Prop2 getting a raft of siblings with added or reduced features is the cost of making each mask set. The existing Prop2 needs to sell more first.
Hub access can be synchronized, after the first, which is more or less random, all subsequent accesses can be calculated (hope to remember correctly) 2 instructions between accesses or every 4 instructions .
or
The P2 is a bit more tricky with the weird hub access scheme, but I think something like that can be used.
waitcnt could be a problem since it may disrupt the synchronization.
Maybe you already tested that and found not working for your needs, just a reminder.
On the subject of chip making progress, I recently read some info, on Wikipedia, that I wasn't expecting. ASML being the sole manufacturer of EUV lithographic equipment for chip making has actually come from fundamental research in USA. There was only two licenses granted from DOE/Congress joint signing after the conclusion of the research back in the 1990s. One was to Intel, which doesn't seem to have developed it, the other went to a small outfit called Silicon Valley Group. SVG was later bought out by ASML.
https://en.wikipedia.org/wiki/Extreme_ultraviolet_lithography
What the article didn't say was whether any special signing off was required for the license/knowledge to be transferred to Europe. I guess there is a lot of sharing of fundamental research between the two anyway.