Time to run my Mac Pro in 64-bit?

You won't really see a huge difference either way. If most of the apps you run are 64 bit then the 64 bit kernel will be *slightly* faster(the processor doesn't have to do as much switching between 64 bit and 32 bit modes), but probably nothing all that noticeable.

Unfortunately Apple has really fallen behind the power curve on their 64 bit transition, largely because they *STILL* haven't created a real 64-bit Quicktime API, they said they weren't going to port the existing Quicktime API to 64 bit but the API they offered in it's place, QTKit, has *maybe* 10% of the functionality of the current Quicktime API(for example you cannot actually do any effects in 64 bit). And even the stuff that you can do with the API actually gets executed on a separate 32 bit process. Apple really should be embarrassed by that API.

It should be 64bit from day 1.

The first few paragraphs of this article may help answer your question.

I've heard of folks that force their kernel in 64 bit mode actually see a decrease in performance. I don't know how true it is though. I just leave my in the default 32 bit mode. Everything runs fine for me like that.

I'll wait on Apple to make the kernel 64 bit mode default.

SandboxGeneral said:

I've heard of folks that force their kernel in 64 bit mode actually see a decrease in performance.

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It seems snappy enough on this 2008 Mac Pro

The 64-bit kernel has been running on this machine for 12 months now.

netdog said:

Early 2008 Mac Pro - 8GB of RAM

but I went to download Handbrake this morning and found a 64-bit version.

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You do know that you can run 64 bit apps in 32 bit mode right?

It depends on the applications you are using. If none of them has problems running on the 64bit kernel, there is nothing which speaks against it. Apples decision to default it on new macs shows that its not just an immature experimental feature.

I have switched to 64 bit kernel six months ago (2008 MP) and didn't run into any issue.

another remark: Do not overestimate the advantage of 64 bit. Of course there are some isolated cases which profit a lot from it, but in general, the speed difference wont be really noticeable, as long as there are still many 32bit apps.