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From: kamath@reed.UUCP
Newsgroups: comp.sys.apple
Subject: Re: Disk ][ <__> ][c
Message-ID: <5476@reed.UUCP>
Date: Mon, 23-Feb-87 20:57:48 EST
Article-I.D.: reed.5476
Posted: Mon Feb 23 20:57:48 1987
Date-Received: Fri, 27-Feb-87 00:26:31 EST
References: <870218205742.619490@HI-MULTICS.ARPA>
Reply-To: kamath@reed.UUCP (Sean Kamath)
Organization: Reed College, Portland, OR
Lines: 60


Beep!


$C019 is VBL.  It goes high during retrace.

I have a picture-wise pin-to-pin description for the disk ][ <-> //c
if anyone wants it.  I used it for a second 5.25 drive for a //c (off a
3.5 incher) just fine.

If you are serious about assembly language, fast algorigthms etc. then
you should get Apple Assembly Lines (the newsletter.)  Fer instance, a
month ago Woz recoded the bascalc routines.  it take about 5 - 6 less
bytes then the Applesoft ROMS and is about twice as fast (approx 36
cycles or so).  I put it in an EPROM, along with a slight Monitor mod to
allow dropping into the moniter on a reset (only if the OA key is held
for more than a second tho!), no problems and a slight bit fast in
applesoft.
I have a 76 cycle divide by seven routine I use in a dhgr program.

a branch takes 3 cycles if succesful, not 2.  it takes 2 if not
succesfull.

ASCI Express is a little brain damaged.  It only does XOR checksumming,
true.  But it PRINTS the crc after the transmission. (ug).  Also, the
very first thing AE tries to do is tell the receiving system what type
of file is being sent.  the first four bytes are:

81 00 00 81 (text)
81 01 01 81 (Applesoft?)
81 02 02 81 (integer?)
81 04 04 81 (binary)

I'n not positive about it, because I finally got sick of it and bought
modem MGR, which also has it's own special version of xmodem, but at
least it gives me the option of using boringly normal old fashion
xmodem.  I also have a few xmodem routines in C, as well as some
translation scripts to convert to blesed ASCII (7 bit) and Apple
standard.

well, that's all I can think of for the moment.

I think I will post the dhgr routines.  I have to make some major mods
to it, as I got it out of a magazine (now defunct I think.  Apple
Orchard) and they are a tad slow (basically conversions of the
programmers aid. ) Fer instance, the ROMS use a subtract 7 routine to
find the remainder.  this is fine and dandy, and it's very small.  on
the other hand, it you are dividing FF, you have to loop 37 times, or
about 37*10 cycles.  To put it in human terms, calling this routine 100
times from applesoft take 20 seconds.  for the fast div by 7 , it only
takes 8.

You can clear the screen up to 4 times faster without a significant
amount of extra bytes if you do it the long way.

just some thoughts.

Sean Kamath

tektronix!reed!kamath