DOS ain't dead

IRQ ISR IDT [5] RM ISR vs PM ISR (DOSX)

posted by DOS386, 19.08.2007, 07:46

> No. You won't gain much by modifying IDT directly. The 180 kHz limit is
> mainly caused by a slow! write to the video memory inside the ISR. A
> real-mode version of the test program - where calling the ISR is done
> without overhead - also stopped at the very same frequency.

Thanks for this additional info ... since you hadn't mentioned the content of your test ISR I just had assumed it would be dummy ... and the 10'000 cycles wasted by the "overhead" only

But I have some doubt how reliable the test against RM is ... since 80486 CPU's are optimized for 32-bit PM performance and the 16-bit RM performance is known to be poor ... "minimal correctness" is considered as sufficient. Thus, the PM version could waste "much" time in the overhead, and the RM version the accidentally very same amount of time because of poor performance of "ordinary" instruction execution

---
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Complete thread:

• IRQ ISR IDT - DOS386, 13.08.2007, 07:05 (DOSX)
  • IRQ ISR IDT - Japheth, 13.08.2007, 08:18
    • IRQ ISR IDT [2] - DOS386, 13.08.2007, 08:34
      • IRQ ISR IDT [2] - Japheth, 14.08.2007, 22:24
        • IRQ ISR IDT [3] Very weeeird results - DOS386, 16.08.2007, 10:28
          • IRQ ISR IDT [3] Very weeeird results - Japheth, 16.08.2007, 14:24
            • IRQ ISR IDT [4] Missed the point - DOS386, 17.08.2007, 00:58
              • IRQ ISR IDT [4] Missed the point - Japheth, 17.08.2007, 10:50
                • IRQ ISR IDT [5] RM ISR vs PM ISR - DOS386, 19.08.2007, 07:46
                  • IRQ ISR IDT [5] RM ISR vs PM ISR - Rugxulo, 21.08.2007, 03:16
                    • IRQ ISR IDT [5] RM ISR vs PM ISR - Japheth, 21.08.2007, 08:28
                      • IRQ ISR IDT [5] RM ISR vs PM ISR - Rugxulo, 22.08.2007, 00:13
                        • IRQ ISR IDT [5] RM ISR vs PM ISR - Steve, 23.08.2007, 13:42
                          • IRQ ISR IDT [5] RM ISR vs PM ISR - rr, 23.08.2007, 15:25
                            • IRQ ISR IDT [5] RM ISR vs PM ISR - Steve, 24.08.2007, 01:11