Date: Mon, 27 Feb 1995 14:19:16 +0500 From: hvb AT netrix DOT com To: THE MASKED PROGRAMMER Cc: djgpp AT sun DOT soe DOT clarkson DOT edu Subject: Re: One More Confused Interrupt Question References: <0098C9C2 DOT 01C1C057 DOT 2 AT bsa DOT bristol DOT ac DOT uk> THE MASKED PROGRAMMER writes: > > (i) What is the difference between a Real Mode interrupt and a Protected Mode > interrupt. > Real mode interrupt relates to the time that the interrupt occurs, the processor is in real mode. If you want your protected mode to execute some of the code at this time you need to hook the protected mode code to the real mode interrupt. So I guess you know what is the Protected mode interrupt is. One catch is you need to call the DOS interrupt every so often from the protected mode to keep the DOS clock running. > (ii) Why, when I use the example from the documentation (which hooks the clock > tick and uses it to increment a volatile int) does the int seem to > increase (a) erratically and (b) far more slowly that 18.3 times per > second. > > (iii) If I use the provided _go32_* functions do they put a lot of overhead > into the interrupt servicing ? > Yes it does add some overhead but I do not know how much. I know that if your clock interrupt uses a lot of processing time, you get some weird behavior and the system eventually hung. We actually reprogram the clock to have 1ms interrupt. It has been working, however, recently we had one or two system hung problem, which I guess it is due to this interrupt. Hope this helps. Hung. ============================================================== Hung Bui Internet: h DOT bui AT ieee DOT org Netrix Corporation Phone: +1 703 793 1016 13595 Dulles Technology Drive Fax: +1 703 713 3805 Herndon Va 22071 ==============================================================