[nycbug-talk] 1U Server Recommendations

[Bob Ippolito]

On Jan 12, 2005, at 0:21, Sunny Dubey wrote:

> On Tuesday 11 January 2005 23:50, alex at pilosoft.com wrote:
>
>> Keep in mind that on 64-bit architecture, you will need about twice as
>> much RAM to get similar performance as on 32-bit architecture. If 
>> your app
>> requires 2G to get decent performance on i386, you'll need 4G on 
>> x86_64.
>> Prices on Xeon and AMD Opteron 2xx are very close. Motherboards are 
>> too.
>
> can you explain why this is so ?
>
> (I've heard some weird theories about 32bit to 64bit migration in 
> terms of
> performance, mostly from Alpha users though ... )

A 64-bit word has twice as many bits as a 32-bit word, so it has twice 
the storage requirements.  I'm not so sure that "twice as much" is 
really true, because not everything is stored as platform dependent 
words.. but in the increments you buy memory, twice as much is probably 
the best way to do it to be sure.  More memory is good to have, anyway.

Note that this is only relevant for applications that are compiled as 
64-bit, if you're running 32-bit code on a 64-bit processor you will 
have the same requirements.

-bob