[rescue] SS Classic Serial ports
Charles Shannon Hendrix
shannon at widomaker.com
Sat Apr 26 18:38:54 CDT 2003
On Sat, Apr 26, 2003 at 04:03:14PM -0500, Scott Newell wrote:
> At 03:58 PM 4/26/2003 -0400, Charles Shannon Hendrix wrote:
> >On Sat, Apr 26, 2003 at 02:29:51PM -0400, Dave McGuire wrote:
> >> I think the actual issue here is the use of a poorly-chosen
> >> combination of Z8530 crystal frequency and main divider settings which
> >> trashes the rates for high-speed use.
> >That's one issue, yes. The other is a very small buffer and little
> >or no DMA use.
> And interrupt load.
Well, that's a lack of buffer and DMA, but yes.
Interrupt load on the old Sun's can be improved by getting better SCSI
too, I have heard but not verified.
> I read the thread linked at:
Me too, though that's not the only one. This is a frequent topic of
> There was some discussion about seperate clocks, but they're discussing the
> devices (say, a sparc box and a terminal) at each end of the cable not
> sharing a common clock, not that a port on the onboard uart is running two
> different clocks for tx and rx. Of course, this is the situation with
> almost every async comm link, not something specific to the Sun
Hmmmm... I was fairly certain I read a thread where they said that it
was something in the Sun hardware, but I suppose not.
It could have even been email between me and someone else and I've just
> Wonder if I could get 115.2k out of my ss2 (for my webpal hacking) by going
> to an external baud rate clock at the sparc...
There are pins for that, but you'd have to write the code for it.
I think one of the discussions I read pointed out how to modify sources
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