I bought a Q6600 quad processor with Windows XP Pro 64, principally to handle a calculation that takes 50 hours on my other system (Intel T7200 2GHz Core 2 Duo). The software concerfned makes use of multiple processors.

The following highlights are reported here:

1/
I would have expected the 2.4GHz Quad system to deliver a result in around 21 hours (given the relative power). It took 23 hours and I put the difference down to background taks such as anti-virus.

2/
I use Adobe Acrobat quite a lot to render output from a number of sources. It has to be Acrobat 8.x with XP 64 bit. Don't even bother with Acrobat 7.x.

3/
If you're wondering about Internet Explorer 32 bit versus 64 bit - here's the skinny that I have found matters. JAVA. I couldn't find a 64 bit Jave Run Time Environment.

Fortunately, the 32 bit browser works perfectly well in XP 64 Nand with it, JRE 32 bit.

4/
The quad processor is good for only two things (otheriwise nothing runs faster that on any other system of same CPU speed):

1. Multi-threaded applications that can use all available processor power;

2. Your own multi-tasking; such as a DVD burn whilst browsing, or downloading or word processing.

5/
I couldn't see any gain for the 1333 FSB capability of the motherboard over the 667 that I have on the T7200 system. I dare say that might be different on memory and disk intensive applications - but on CPU intensive work, there appears to be no gain from the fast memory.

6/
When installing software, XP 64 places 64 bit applications into Program Files and 32 bit applications int Program Files-x86.

Windows XP 64 SP2 works well enough and I'll add to this post as I see other applicatins perform, particularly from the Adobe stable.

I find that my server with quad pentium 3s and a crappy amount of cache under server 2003 is faster than my core2duo under xp x64. wierd isnt it?

I installed XP 64 on my computer once, and removed it about an hour later because nothing worked. It's now sitting in some garbage dump.

yes, i find that the performance gain isnt big enough to outweigh the downsides

You can find a 64 bit JRE at Sun Developer Network. Download the flavor that you need to match your platform and browser.

Regards

At last. Thanks. That releases a whole load of restrictions out of Internet Explorer 64 - I hope.