PC GAMESS/Firefly-related discussion club

Learn how to ask questions correctly

Alex Granovsky
gran@classic.chem.msu.su

>Thanks! I see that Core i7 (as well as in ixbt benchmarks) works only 10-15% faster than Phenom II x4.

First, note that both Core i7 and Phenom II were not overclocked at all.

Second, the "stream" benchmark gives approx. 1.5 better results
on Core i7 as compared with Phenom II. The not-so-large difference
in performance is mainly because Firefly is well written and is
usually limited by the raw CPU performance, not memory.

>As for Xeon, the only reason to build workstation on Xeon is the
>ability to use 2CPU MB in order to obtain second CPU (with its bank
> of RAM) later.

I see.

> As for SAS HDD or SDDs, I'm afraid we'll never be able to spend
> money for them...

Well, SSDs rapidly become cheaper and cheaper...

> If so, what's the reason to use ECC RAM with Core i7 or Phenom X2?
> (Of course it's obvious to use it with Xeon).

Just to be 200% certain there are no any errors in calculations :-)

>>4. As to SSDs... we are now working on the reoptimization of
>>Firefly's I/O routines for SSDs as we now have very fast SSD at hands
> Are you really sure that SSDs have big enough MTBF?

The SSD I have has 3 years of warranty and 1,500,000 hours MTBF

>And several more questions:

>1. Is call64 option currently available for Phenom II?

Yes it is. It was made especially efficient in the forthcoming version 7.1.G

> How much RAM can Firefly use?

This depends on the OS and on linking type.
There are my previous posts on this topic on the Forum.
Since then, nothing has been changed.

> 2. Is that true that sometimes cache files can be 100-200 Gb
> or more for any CPU core?

Indeed, the size of scratch files can be very large.
E.g., for conventional (not direct) SCF, large-scale MP2, and so on.

However, for direct HF, MCSCF, DFT, CIS, TDDFT etc... one usually do not need much temporary storage at all.

>3. Is there any reason to use SAS HDDs instead of SATA II?

Frankly, I do not think it makes sense to use them for most of the jobs.
However, if you do like to perform conventional SCF or
semidirect MP2, you can consider this option.

> Is there OK to have 1HDD per 2 CPU cores or it's better to use separate HDD per each core.
> Or maybe it doesn't matter and SATA II data transfer rate will be enough for most tasks?

The separate HDDs are better. The problem is not with the transfer
rate, it is rather with disk mechanics and constant disk seeks while
switching between different I/O streams. However having single SSD
drive per two or more cores looks very attractive.


Regards,
Alex Granovsky

[ This message was edited on Wed Sep 9 '09 at 9:58pm by the author ]