Re:Show HN: I made a discrete logic network card
by heinrichhartman on Tuesday April 09, 2024 @07:43AM
(#39978413)
What does "discrete logic" mean in this case? Why would this prevent interrupts?
Re:Show HN: I made a discrete logic network card
by RetroTechie on Tuesday April 09, 2024 @08:48AM
(#39978850)
> What does "discrete logic" mean in this case?
74xx series ICs (eg. 74ACT family in case of the cpu, if I read correctly).
More generally, it may refer to "basic logic elements whose function is easily inspected".
> Why would this prevent interrupts?
Not at all - in theory.
In practice, interrupt support tends to complicate cpu designs. Complicate = more logic = more ICs. So builder decided against it & chose not to implement interrupts on the cpu.
Only nitpick I'd have is that author decided to use a custom-design cpu.
Ok, "discrete logic only!" is a valid choice. And then keeping complexity to a minimum weighs heavily. But the downsides of that choice are also considerable:
-No interrupts (which are very useful)
-No existing software base to tap from. Somewhat-useful C compiler helps.. somewhat.
But who am I to question author's choices for a hobby project like this? Great stuff in any case.