27 Nov
2014
27 Nov
'14
3:41 a.m.
From: Dave Horsfall <dave(a)horsfall.org>
what was the problem with them?
Well, not a _problem_, really, but.... 'one interrupt per output character'
(and no way around that, really). So, quite a bit of overhead when you're
running a bunch of DZ lines, at high speeds (e.g. 9600 baud).
I dunno, maybe there was some hackery one could pull (e.g. only enabling
interrupts on _one_ line which was doing output, and on a TX interrupt,
checking all the other lines to see if any were i) ready to take another
character, and ii) had a character waiting to go), but still, it's still going
to be more CPU overhead than DMA (which is what the DH used).
Noel