Subject: Re: will mac68k work with...
To: None <port-mac68k@NetBSD.ORG>
From: Michael G. Schabert <mikeride@prez.buf.servtech.com>
List: port-mac68k
Date: 01/23/1998 20:17:24
>for a generic ftp server of something.  Will the accelerator speed up the
>disma 9600bps port speed limit??  Thanks.

>No, (well, I doubt it, anyway).  I beleive that's a hardware limitation of
>the serial chips.

>I think it's actually an interrupt latency problem. The clocking itself
>(which baud rates can be generated) didn't change from the original
>mac until the PowerMacs, I think. Maybe the Q/AV ones. But the clocks were
>stable for at least 8 years. The 68000, however, probably can't handle
>many interrupts per second. :-(

First, Sorry for the delay. I went on vacation for New Year's & returned to
around 800 waiting emails & am still trying to crawl out from under them.
Next, let me say that the SE has no "dismal 9600bps speed limit". As Bill
mentioned, the serial clock was UNTOUCHED from the very first Mac until the
AV Macs...i.e. they're ALL 57,600.

Technically, though, the printer port runs at 230kbps (the same as the
GeoPorts), since that's LocalTalk's specification.

 I was using a 14.4kbps on my SE back when AOL only had 4800bps speeds (I
remember when people were SHOCKED at my d/l speeds when AOL upgraded
Buffalo to 9600bps, since we were pretty early on the list). On a text
file, it had no trouble with full serial speeds, & binary transfers
(zmodem) averaged 1570 chars/sec or so as told by Zterm. The same modem
didn't go any faster when I got my Quadra 840 AV with its 230kbps serial
speed.

The only Mac that I know of that can't sustain serial transfers is the
original Mac LC. It had a bug in its serial logic that caused slowdowns,
well-documented in TIL. If you want to run Un*x on the SE, you may want to
try MacMinix without upgrading the processor (MacMinix only runs on 68000).
If I remember right, you can also run MacMiNT on it under MacOS, but it's
been about 3 years since I played with either of those, since NetBSD is
much more mature.

===============

Note that the above is in reference to HARDWARE limitations. Unfortunately,
NetBSD limits the system a lot more. As Bill mentioned, he gets overflows
using a IIsi at 57,600. Basically, NetBSD, because of the way that the
pre-emptive multitasking works, pays a lot less attention to the serial
ports than MacOS. In MacOS, they get much priority even if an application
is hogging the processor.

HTH
Mike


ps. to the guy who wanted to connect the StyleWriter 1200...you mentioned
that AppleTalk slowed your Mac to a crawl...I've never seen it have ANY
appreciable impact on the speed of a machine in my vast Mac experience.
Perhaps you mean that running PrinterShare slowed the Mac to a crawl. That
is the effect of the software router, not AppleTalk.

Bikers don't *DO* taglines.