notes@harpo.UUCP (01/25/85)
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.
ee65xdh@sdcc7.UUCP (JAMES HAYES) (01/27/85)
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. ------------------------------------------------------------------ Me: James Hayes US Snail: P.O. Box 7378, La Jolla CA 92037 Net: {ucbvax,sdchema,inhp4,ucivax, bmcg,sdcrdcf,akgua}!sdcc7!ee65xdh ------------------------------------------------------------------ ~Speed isn't everything. You have to be right some of the time.. :-) ~