Sent from my iPhone
> On Nov 1, 2022, at 10:01, Wayne S <wayne.su...@hotmail.com> wrote: > > Hi Paul. Who “corrected” you about DMA input? I’d like to read about that as > nothing i read about the DZ mentioned that. Got any Cites? > > Sent from my iPhone > >> On Nov 1, 2022, at 09:01, Paul Koning via cctalk <cctalk@classiccmp.org> >> wrote: >> >> >> >>>> On Oct 30, 2022, at 2:49 PM, Wayne S via cctalk <cctalk@classiccmp.org> >>>> wrote: >>> >>> The difference between dz and dh interfaces is that the dh used dma instead >>> of interrupts to get characters to the cpu. It would be transparent to any >>> software. >> >> No, it doesn't. I was confused about this but was recently corrected. >> >> The DH11 does DMA output, but not DMA input. I don't know any DEC serial >> port devices that have DMA input; it would make very little sense to do that >> since input generally is one character at a time. Block mode terminals do >> exist in DEC's world but they are rare, and even those are hard to operate >> with simple DMA. >> >> DZ is programmed I/O in both directions, which makes the difference. In >> typical usage, the bulk of the terminal traffic is output, so doing that >> with DMA is a big win. >> >> paul >> Also, can you define what the phrase “programmed io” refers? AFAIK, pretty much everything does that, so a clarification would help. >>
