[gmx-users] 8MB CPU cache vs 4MB CPU cache: large difference in performance?

[Yang Ye]

On 9/9/2007 10:08 PM, David van der Spoel wrote:
> Yang Ye wrote:
>> Cache size matters because it ensures a steady data/instruction flow 
>> to feed the "hungry" CPU, especially with Intel Coreo architecture. 
>> With database-type application, larger cache benefits much. In case 
>> of GROMACS, unless you deal with very large system, I doubt its 
>> effectiveness. It could be better to run some real-world benchmarks. 
>> Or look for benchmark that contains software operating in a similar 
>> way of GROMACS, e.g. scientific benchmark, multimedia benchmark 
>> (decoding/3D rendering, with SSE boost).
>
> but note that you now get four cores that share the cache, so 1 
> Mb/core or 2Mb/core. That does matter. For an honest comparison you 
> should compare (price with 8Mb/price wih 4Mb) / (Performance 8 Mb / 
> Performace 4 Mb), where performance is in ns/day. I would think that 
> 60$ extra per chip is worhtwhile.
Yes. This is a good note. I agree with David.
>
>>  
>> Regards,
>> Yang Ye
>>
>>
>> ----- Original Message ----
>> From: Frankie Montenegro <frankie.montenegro at gmail.com>
>> To: gmx-users at gromacs.org
>> Sent: Sunday, September 9, 2007 7:08:54 AM
>> Subject: [gmx-users] 8MB CPU cache vs 4MB CPU cache: large difference 
>> in performance?
>>
>> Hi,
>>
>> I am about to purchase several units with Intel's quadcore q6600
>> processors. Since about 80% of our work is done with Gromacs, I
>> figured this list is a place to ask performance questions.
>>
>> I was wondering if there would be any significant benefit in having a
>> q6600 processor with 8MBof L2 cache over the identical processor
>> with 4MB of L2 cache. The price difference is about 60$,which doesn't
>> seem much,  but could pile up if we end up buying more then a few units.
>>
>> Thanks for your help.
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