Message-ID: <2655@harpo.UUCP>
Date: Thu, 24-Jan-85 21:11:44 EST
Article-I.D.: harpo.2655
Posted: Thu Jan 24 21:11:44 1985
Date-Received: Fri, 25-Jan-85 09:23:06 EST
Sender: notes@harpo.UUCP
Organization: AT&T Bell Laboratories, Whippany
Lines: 4
Nf-ID: #N::37600017:000:203
Nf-From: !bob    Jan 24 15:39:00 1985

Can anyone comment on their experience -good or bad- at using the Super
Serial Card with a 1200 boud modem.  Several people have said that
it loses characters, but I find this a little hard to believe.

Message-ID: <1350@sdcc7.UUCP>
Date: Sat, 26-Jan-85 19:14:33 EST
Article-I.D.: sdcc7.1350
Posted: Sat Jan 26 19:14:33 1985
Date-Received: Mon, 28-Jan-85 06:46:25 EST
References: <2654@harpo.UUCP>
Reply-To: ee65xdh@sdcc7.UUCP (JAMES HAYES)
Organization: U.C. San Diego, Academic Computer Center
Lines: 43
Summary: 

In article <2654@harpo.UUCP> bob@harpo.UUCP writes:
 >  Can anyone comment on their experience -good or bad- at using the Super
 >  Serial Card with a 1200 boud modem.  Several people have said that
 >  it loses characters, but I find this a little hard to believe.

The Super Serial card is not at fault. It can handle a heck of a lot
more faster baud rates than 1200. The problem is the Apple's
screen hardware and supporting routines.

The //e, more so than the //c has problems in the 80 column mode.
The display is memory mapped in an interlaced fashion. Half of the
screen is stored on the card in the AUX slot and half is stored on
the regualar text page. (That's why when you hit reset, you get
every other character on the 80 column screen.) Ok, to access the
other AUX page of display memory, you must store to two memory
locations. One tells the card to sense for the second location. The
second location toggles the region of memory you want to use. (both
are mapped into the SAME $400-$7FF range.)

Ok, that doesn't sound two bad, but that means to scroll, you must
access 2 switches, 1100 memory references, another switch, 1100 more
references, and some more to clean up the last line. THAT'S AN AWFUL
LOT OF TIME TO DO THAT. 1200 baud just can't keep up.

On top of that, Apple didn't optimize the routines on the //e. I
haven't verified, but the //c's screens appear to scroll much
faster. 

I reccomend a better solution made by Computer Stop of Hawthorne,
CA. They make an 80 column card (about $99 on sale) that does all
the display updating in HARDWARE, so when I want it to scroll, I
need ONLY 4 MEMORY REFERENCES. Truly an improvement. 

'nuff said.
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