Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!killer!elg
From: elg@killer.UUCP (Eric Green)
Newsgroups: comp.sys.cbm
Subject: Re: 2400 Baud on a C64?
Message-ID: <4727@killer.UUCP>
Date: 7 Jul 88 03:58:17 GMT
References: <5087@orstcs.CS.ORST.EDU> <10455@dutyche.cair.du.edu> <4663@killer.UUCP> <5640@sgistl.SGI.COM>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 29

In message <5640@sgistl.SGI.COM>, larry@sgistl.SGI.COM (Larry Autry) says:
>In article <4663@killer.UUCP>, elg@killer.UUCP (Eric Green) writes:
>> Skyles  interface, instead of serial interface). Not to mention that
>> screen display at 9600 baud is pretty impossible on a 1mhz 6502 (960
>> characters per second? hmm, that leaves, err, 100 cycles to input a
>> character and display it). 
>Please explain how the Apple II performs this magic given that it has the
>same 1 mhz 6502?  ( This is not an invitation to a hardware flame-fest
>since the old OSI did the same magic).  I believe that it has much to do 
>with the screen driver.
>
>-- 

References: 1mhz clock = 1,000,000 cycles/second, /960 bytes/sec =
1,000 clock cycles per byte. Darn. Lost a zero.

So it does appear that screen display could occur at 9600 baud (hey,
what am I saying, it DID occur at 9600 baud). However, scrolling could
not be done fast enough at 9600 baud (copying 1K of RAM in 1,000
cycles is impossible, obviously), which is the same situation that
faces people using Kermit-64's fake 80 columns at 1200 baud -- that
is, unpleasant, but still workable.

Ahwell, I plead overwork :-).

--
Eric Lee Green    ..!{ames,decwrl,mit-eddie,osu-cis}!killer!elg
          Snail Mail P.O. Box 92191 Lafayette, LA 70509              
       MISFORTUNE, n. The kind of fortune that never misses.