cpu-cycles

I am planning on creating a Sega Master System emulator over the next few months, as a hobby project in Java (I know it isn't the best language for this but I find it very comfortable to work in, and as a frequent user of both Windows and Linux I thought a cross-platform application would be great). My question regards cycle counting; I've looked over the source code for another Z80 emulator, and for other emulators as well, and in particular the execute loop intrigues me - when it is called, an int is passed as an argument (let's say 1000 as an example). Now I get that each opcode takes a

What is the difference in CPU cycles (or, in essence, in 'speed') between x /= y; and #include <cmath> x = sqrt(y); EDIT: I know the operations aren't equivalent, I'm just arbitrarily proposing x /= y as a benchmark for x = sqrt(y) osgx The answer to your question depends on your target platform. Assuming you are using most common x86 cpus, I can give you this link http://instlatx64.atw.hu/ This is a collection of measured instruction latency (How long will it take to CPU to get result after it has argument) and how they are pipelined for many x86 and x86_64 processors. If your target is not

The Intel manuals for the RDTSC instruction warn that out of order execution can change when RDTSC is actually executed, so they recommend inserting a CPUID instruction in front of it because CPUID will serialize the instruction stream (CPUID is never executed out of order). My question is simple: if they had the ability to make instructions serializing, why didn't they make RDTSC serializing? The entire point of it appears to be to get cycle accurate timings. Is there a situation under which you would not want to precede it with a serializing instruction? Newer Intel CPUs have a separate