h235_131@ccvax.ucd.ie (04/29/91)
I have an 8MHz XT clone with the following problem - it squeals. The squeal
emanates from the general direction of the speaker, but is essentially
unaffected by the volume control. It is only present when the machine waits for
input via DOS (but vanishes when eg Sidekick is loaded.)
Old age and irritability mean I can stand it no longer. I have found that it is
DOS's repetitive INT 16h'ing which causes the noise, & can duplicate the squeal
with the following code:
L1: MOV CX,68h ; Experimental figure.
L2: LOOP L2
MOV AH,01 ; Key pressed?
INT 16h
JZ L1 ; Nope.
SUB AH,AH ; Yes,
INT 16h ; flush it.
It's not system interactions with the STIs and CLIs; coding the INT 16h routine
in RAM eliminates the squeal - despite tinkering with the loop value to account
for RAM/ROM speeds. Experiments with other BIOS routines also produced the
squeal when in ROM, but not RAM.
So there you have it. Can anyone tell me what's causing this, and how to get
rid of it? I know I can shove some spoiler code in INT 28h to increase the
delay between reads (DOS only), or recode the whole BIOS in RAM, but ugh!
While I'm about it, are there any GIFs of E&S simulator stills etc? And can
anyone recommend a good article on optimising DES 'in the large'? I have a
little routine doing 4K/s on my XT, but I understand 10K/s is feasible so I'm
missing something *big*! Also, are there restrictions on diffusing DES code on
this side of the puddle - the local embassy doesn't know.
Thanks in advance... EMAIL replies please.
Doug. "We are the music makers, and we are the dreamers of dreams."
- Willy Wonka, obviously an assembly programmer!