Mail Archives: djgpp/1996/02/05/10:57:20
James T. Sweeten Jr. (sweeten AT belgarath DOT nwscc DOT sea06 DOT navy DOT mil) wrote:
: I have a question concerning the timer interrupt 8.
: What is the difference between the protected mode int8 and the real mode
: int 8?
: I need to output a value on a d/a board at specific intervals. I
: originally did this with borland by installing my own timer interrupt routine.
: I was able to get down to 100 micro second (10khz) resolution. I am trying to
: do the same thing using djgpp. I have read the faq and have also gotten
: pctime13.zip (This has milisecond resolution for djgpp). I modified the
: interrupt routines in pctime13.zip, (gccint8.c), to output the data to the
: d/a board ok but I can't get down to 100 micro second resolution. With an
: input value of 3000 hz I get a nice 1500 hz square wave. With a value of
: 4000 hz it works for a while but then locks the machine up. Any help would
: be appreciated.
: I am using 1.12m4 on a 486/66.
I recently had exactly the same need, tried just what you did (also on a
2/66), and got almost the same results. Mine sometimes even hung at 3000.
Apparently, the overhead of the DPMI stuff is just too great for high
frequencies. I gave up on djgpp and did it in real mode. I can do 20Khz
with no problems.
- Raw text -