Xref: news2.mv.net comp.os.msdos.djgpp:801 From: larryb AT comtch DOT iea DOT com (Larry Blanchard) Newsgroups: comp.os.msdos.djgpp Subject: Re: Timer interrupts Date: 4 Feb 1996 17:55:04 GMT Organization: CompuTech Lines: 21 Message-ID: <4f2rto$dbp@krel.iea.com> References: NNTP-Posting-Host: comtch.iea.com To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp 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.