[rescue] SS Classic Serial ports

[Charles Shannon Hendrix]

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:
> http://mail-index.netbsd.org/port-sparc/1999/10/

Me too, though that's not the only one.  This is a frequent topic of
discussion.

> 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
> implementation.  

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
forgotten.

> 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
for this.


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