Re: [gentoo-user] PCIe x1 or PCIe x4 SATA controller card

[Rich Freeman <rich0@gentoo.org>]

On Mon, Mar 27, 2023 at 6:37 AM Frank Steinmetzger <Warp_7@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