[rescue] SS Classic Serial ports
Charles Shannon Hendrix
shannon at widomaker.com
Wed Apr 23 19:00:56 CDT 2003
On Wed, Apr 23, 2003 at 11:29:25AM -0400, Curtis H. Wilbar Jr. wrote:
> The box is capable of the high serial port baud rate (57600 or 115200),
> but I can't say how well it will work/etc as I have never tried it.
Then you don't know if it will work... :)
It most assuredly will not.
The pre-PCI Suns can only manage 0-38.4Kbps reliably.
They can lock in 51200bps, but its not very reliable, and most modems
won't use that speed.
They can also do 76800bps, but again, most modems won't run at that
That's as fast as you can go without getting so horribly unreliable that
nothing works well.
Now, that's not because the chips are so terrible, but because Sun did
odd things in the implementation. They use seperate clocks for in and
out, which drift and every N frames cause an error at high speeds.
You are supposed to be able to give them an external clock on one of the
serial port pins, and get higher speeds, but I don't know of anyone who
has done this, just a lot of talk between various serial code hackers
like der Mouse on the netbsd lists.
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