Performance analysis for DOS apps?

Michael B. Brutman wrote: #1 assembler optimization rule for old DOS apps: Keep everything in registers. Memory accesses are really slow for everything 386 and below. If you have to pass data to other blocks of code, try to do so via registers instead of the stack. #2 assembler optimization rule: inline code with macros where it makes sense. A CALL on 8088 is 70 cycles (less penalty the more modern the CPU gets, but still), plus it's that many less JMPs/RETs/etc. Other helpful hints include: - Smaller code is usually faster (see the "memory reads suck" rule) - JMPs suck (they empty prefetch queue and flush caches) so try to make the most common case in a comparison-and-jump the "fall-through" case Turbo Profiler, although I've never tried profiling a TSR. You can profile sections of code yourself by reading the 8253 timer both before and after a block executes, then subtracting. Mail me if you'd like some example code. The timer counts from 65535 down to 0 about 18.2 times every second; if the code you're profiling executes in less than 55ms, then you can do your own microsecond-accurate timing. -- Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/ Help our electronic games project: http://www.mobygames.com/ Or check out some trippy MindCandy at http://www.mindcandydvd.com/ A child borne of the home computer wars: http://trixter.wordpress.com/