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1988-01-16
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88 lines
A2001sdm.txt
16 Jan 88
S.D. Maley
see also: a2000sdm.zoo
This is a follow on to the observations made in a2000sdm.txt (not
to be confused with a space odyssey -- at least outer). Included
in this zoo:
spdhlt.asm: Safely brings bridge floppy speed up to normal,
spdhlt.com
speed.com: For the more adventurous, drops the step rate.
Remember: If you move .com files between Ami and PC sides, use the
/b (binary) switch with Aread or Awrite.
Corrections/Addendums to a2000sdm.txt
-------------------------------------
o Micro Emacs 3.9e, compiled with Lattice C 4.0, works fine.
The Manx compiled version still requires NoFastMem. If I get
ambitious, could try to write code into the Ami version to
accept input from the clipboard. As it stands, I can cut and
paste between PC side programs (including Emacs, but I could
already do that). The only clipboard-aware program on the Ami
side that I might use is notepad. It would be very nice to bridge
from PC side Emacs to Ami side Emacs (for those of us who must work
in both worlds).
o The video bios is about the same speed as a "real" XT,
_not_ 12% faster (the benchmark (pctest) was against a flat PC),
o The number (239) quoted for the floppy step rate set by speed
should really have been shown in hex. It is a two byte value
that represents more than the step rate. What speed does is
reduce the step rate from 4 msec (DF) to 2 msec (EF) (not very
intuitive, is it ? Refer to an IBM PC AT technical reference,
or maybe one of Norton's books, if you want to know what it is).
This is great for short steps, but can result in banging the stops
for stepping all the way across the floppy (as it says above:
"For the more adventurous ...").
o Directory Scanner 3.00 is the only PC program I've found that
won't work with my bridgeboard setup. DS uses a device driver
for speeding up access to the hard disk file tree. This doesn't
work with a virtual PC hard disk. Either DS or the Amiga driver
(jdisk.sys) aren't playing by the same rules.
o On rare occasions, garbage characters will flash by while the PC
side text display is scrolling. Generally, if you keep typing
the junk will go away sooner or later. However, the garbage may
be related to a lockup situation that sometimes happened on PC boot
(garbage was all over the screen when the PC window was opened).
The lockup only occured right after bringing Ami in from the cold
(after leaving her in the backseat of the car all night).
Further observations
--------------------
The A2088 bridgeboard that led to some of the difficulties noted
(in a2000sdm.txt has been replaced. Since then I have not pulled
the cover to reseat things even once.
While the bridge was out, I tried to get Transformer going on the
A2000. There is apparently some kind of timing problem in the
software. Transformer gets to Dos (MS 3.2 or PC 3.3) ok, but
Dos says it has no empathy with the floppy in drive A: (the drive
light then stays on. Also noticed that Transformer reported that
"Available memory: D47K" (and you thought it was wispering _decimal_
sweet nothings in your ear, ...)).
The only major complaint I still have is the virtual disk handling.
Caveat 1 still holds: If you do file transfers between a real hard
disk on the Amiga side, and a virtual disk (linked to that hard disk)
on the PC side, you will get into a _MESS_ ! The best way out, if
you realize what you've done is to _immediately_ warm boot the
Amiga (not the PC side): <Ctrl><Amiga><Amiga>. That way, if you
were AWrite(ing), the only problem will be an empty file on the
Amiga side.
If you don't warmboot, you may be misled by MS Dos reports of problems
with the virtual disk file structure. You may be informed that all kinds
of files (possibly anywhere along the file tree branch you refered to with
AWrite) are either missing or corrupt.