Intel Celeron G540 vs Intel Celeron G540: from -0.2 to 209% difference in CPU tests!

[igoryan]

Intel Celeron G540 vs Intel Celeron G540: from -0.2% to 209% difference in CPU tests! Tell me please how it can be?

[David (PassMark)]

Check for differences like,
- Overclocking
- Different RAM speeds & different RAM channel setups
- Background tasks running on the machine
- CPU overheating and throttling.

[igoryan]

Thanks.

Overclocking - Negative.
Background tasks running on the machine - Negative.
CPU overheating and throttling - Negative.

Different RAM speeds & different RAM channel setups - how memory can affect a three-fold loss of Prime Numbers?
Both PC-10600, but my PC - Win 7 32 bit with 2x2 GB RAM and compared PC - Win 7 64 bit with 2x4 GB RAM.
Can be the key difference in operating systems? I think that not so much.

[David (PassMark)]

It is the 32bit / 64bit difference that is causing the difference in the benchmark results.
This should have been something I added to my initial list of things to check above. We switched to fully using 64bit years ago, so I haven't seen this behaviour for a while (i.e. low prime number benchmarks and low integer benchmarks)..

Some of the tests use 64bit variables in their algorithms (as is common nowadays). Doing 64bit maths on a 32bit CPU is very slow. For example, the Prime Number calculation makes heavy use of square roots of 64bit numbers.

You can find further discussion on the topic in this 11 year old post on 64bit benchmarking and this one on Instruction mix.