[simh] RSTS processor identification

Johnny Billquist bqt at softjar.se
Fri Mar 5 21:08:50 CST 2021

On 2021-03-06 03:22, Eric Smith wrote:
> On Fri, Mar 5, 2021 at 6:33 PM Paul Koning via cctalk 
> <cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>> wrote:
>     I would have liked better comms.  The USART has such a tiny FIFO
>     that you can't run it at higher than 9600 bps even with the J-11
>     CPU.  At least not with RSTS; perhaps a lighter weight OS can do
>     better.  The printer port is worse, that one can't run DDCMP
>     reliably at more than 4800 bps.  I normally run DDCMP on the PC3XC,
>     which is a 4-line serial card that uses two dual UART chips (2681?)
>     with reasonable FIFO.
> There seem to be a great many models of Unibus and Qbus multi-port async 
> serial boards, which present different register-level interfaces, e.g. 
> for Unibus, DH11, DHU11, DJ11, DM11, DZ11 . Which ones are considered 
> "best", for each bus, for use with a multitasking OS like RSTS/E or 
> RSX-11M+?

In general, you should pick a controller that can do as much as possible 
with DMA.
Which means DH11 or DHU11 for Unibus.
Similar with Qbus: DHV11.


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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