about interlagos

about interlagos

[Mahmood Naderan]

There are three opteron processors with the cpuid that I paste below:
model name    : AMD Opteron(tm) Processor 6136 (magny core, 8)
cpu MHz        : 800.000
cache size    : 512 KB
bogomips    : 4800.20

model name    : AMD Opteron(tm) Processor 6174 (magny core, 12)
cpu MHz        : 800.000
cache size    : 512 KB
bogomips    : 4400.13

model name    : AMD Opteron(TM) Processor 6274  (interlagos, 16)
cpu MHz        : 1400.000
cache size    : 2048 KB
bogomips    : 4399.97

As you can see, although interlagos is the newest one which has higher cpu 
clock rate and higher cache size, the bogomips of interlagos is the lowest!
I read that bogomips is not a true measurement, but it senses as a speed meter.
Any idea?

~MN

Re: about interlagos

[Clemens Ladisch]

Mahmood Naderan wrote:
> As you can see, although interlagos is the newest one which has higher cpu
> clock rate and higher cache size, the bogomips of interlagos is the lowest!
> I read that bogomips is not a true measurement,

Indeed it is not.

> but it senses as a speed meter.

It measures the speed of one particular delay loop.  Because such a busy
loop is pretty much the silliest thing you could do to a CPU, it does
not make sense to use it to measure overall CPU speed, or to compare
different microarchitectures.

> Any idea?

If you want to know how fast your code will execute, you have to measure
that code.  If you are too lazy to do this, search for a benchmark that
represents that code well; for general-purpose code, the gcc part of the
SPEC CPU benchmark probably comes closest.


Regards,
Clemens

Re: about interlagos

[Mahmood Naderan]

Thanks
// Naderan *Mahmood;


----- Original Message -----
From: Clemens Ladisch <clemens@ladisch.de>
To: Mahmood Naderan <nt_mahmood@yahoo.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Sent: Saturday, June 16, 2012 1:50 PM
Subject: Re: about interlagos

Mahmood Naderan wrote:
> As you can see, although interlagos is the newest one which has higher cpu
> clock rate and higher cache size, the bogomips of interlagos is the lowest!
> I read that bogomips is not a true measurement,

Indeed it is not.

> but it senses as a speed meter.

It measures the speed of one particular delay loop.  Because such a busy
loop is pretty much the silliest thing you could do to a CPU, it does
not make sense to use it to measure overall CPU speed, or to compare
different microarchitectures.

> Any idea?

If you want to know how fast your code will execute, you have to measure
that code.  If you are too lazy to do this, search for a benchmark that
represents that code well; for general-purpose code, the gcc part of the
SPEC CPU benchmark probably comes closest.


Regards,
Clemens