On Mon, Mar 27, 2023 at 6:37 AM Frank Steinmetzger <war...@gmx.de> wrote: > > Bogomips seems to be veeeery simple, because it takes the current frequency > into account. So the number will be low when your PC idles and very high > when you compile something. The “bogo” stands for bogus for a reason. >
Just to add to this, you need to also keep in mind its purpose. The kernel needs to be able to measure timings that wouldn't make sense to measure using a timer chip (lots of reasons for this). So it uses a timer chip to calibrate a delay loop. I don't know what instructions are being executed in the delay loop but the obvious design goal with a delay loop is maximum consistency with a short enough time per iteration that you have sufficient resolution. The BogoMIPS output is just telling you what the calibration factor was for each cycle of the loop. It is about as synthetic a benchmark as you can get, and it measures how quickly your CPU can execute code designed to do nothing more than waste time. > > Of course, only you can answer that in the end. Write down what you need and > what you care about. Weigh those factors. Then decide. Raw CPU power, > electricity bill, heat budget (cooling, noise, dust), the “new and shiny” > factor (like DDR5), and price. As I mentioned earlier, the 7xxx-X series are > hotheads. But when run with a lower power budget, they are very efficient > (which is basically what the non-X do). Are they actually hotheads on an energy consumed per unit of work basis? As you say, they're efficient. If the CPU has 2x the power draw, but does 2.5x as much work in a unit of time than the "cooler" CPU you're comparing it to, then actually doing any job is going to consume less electricity and produce less heat - it is just doing it faster. Max sustained power draw matters for cooling and electrical design (the latter being something users typically don't try to change). It isn't really a measure of thermal efficiency since that requires incorporating some measure of work getting done. A recent trend is upping the power draw of CPUs/GPUs to increase their throughput, but as long as efficiency remains the same, it creates some thermal headaches, but doesn't actually make the systems use more energy for a given amount of work. Of course if you throw more work at them then they use more energy. -- Rich
