On Tue, 11 May 1999, Jonathan Stone wrote:

> >I doubt it's Zilog vs. AMD or clock divider (if you were still running the
> >BRG and the channel in /16 mode). mac68k uses AMD chips in some machines,
> >and Zilog cores in others. All have been able to run at 57600 baud, which
> >uses the same divider constant (0) as 115200 on pmax.
> 
> I dunno.  This was the same machine where i still had to put in the
> DELAY() macros for 1.6 usec onchip settle time.  Someone told me quite
> rudely that the DELAY()s weren't necessary because the problem was
> "fixed in hardware".  Maybe on Alphas it is, but not on the first
> 5000/240 I brought up.

Ewwwww. EVERY access needs the delay macros if it's not fixed in hardware!

> >I thought you were playing with /1 mode at one point? THAT will definitely
> >cause problems. :-)
> 
> I was, but I'm pretty sure this was with 16-sample mode with the
> divisor set to 0. I think 78.6 didnt work on this particular machine
> eihter.
> 
> IIRC we'd have to go to 1-sample mode to go to 230k, but that's synch
> anyway. Or does localtalk provide an external clock?

LocalTalk would need an external clock source for non-mac hardware.
LocalTalk ignores the BRG, and runs the transmitter in /16 mode and the
receiver in /16 PLL mode (off of the receive clock). Thus a 3.68 MHz clock
needs to be available, which I think isn't at present.

Take care,

Bill