If you have 3GB of RAM or less, there's no real point in running 64-bit. 4GB is borderline however.

Mr. Ben is waiting on his gigarams to arrive.

I, however, run 2GB on 64-bit fulltime. There's more to running a 64-bit OS than being able to access more RAM.

But I don't see the disassembly of current C compilers making good use of all those additional (and larger) registers.

Faster 64 bit arithmetic comes to mind.
My chess program is about 50% faster in 64 bit mode than in 32 bit mode, for instance.

My chess program is about 50% faster in 64 bit mode than in 32 bit mode, for instance.

You're using bitfields for the 64 positions? Actually my bignum calculator is 4x faster for multiplying since it can do 64 bit multiplies in one fell swoop instead of high/low/high/low, but this sort of thing isn't needed often.

[EDIT]

I like to push test programs to the limit to see what happens. Here I "drew" 100000000 lines of text to make sure my scrollbars worked right.

{"name":"7Ie3O.png","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/4\/7\/4789e79bfb9428c810d8aca23d42a36a.png","w":831,"h":618,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/4\/7\/4789e79bfb9428c810d8aca23d42a36a"}

[EDIT2]

I just calculated that for a monitor to show all those lines at once would be ~531km high. I have an old TimexSinclair 2000 with 2 kilobytes of ram, when you get to about 50 lines of BASIC typed in, the previous characters start disappearing instead of showing more because it's running out of ram. We've come a long way in 20 years...

The gcc compiler (maybe all 64 bit compilers) exclusively use the SSE registers for all floating point calculations, I've used the f87 registers without problems in assembly language (they don't get trashed).

Yeah, after demonicmaniac told me to look at thinkwiki for unoffical ram specs of my thinkpad, I'm probably going to upgrade to 8G on this laptop. I just have to buy two $80 4G DDR2 SO-DIMM modules.

I know, but I haven't benchmarked how much of a speedup that gives for 64 bit mode (if any).

But are slower, right?

Shame. I upgraded the RAM in my MacBook to 4GB (from 2 GB) less than two weeks ago.
Makes a nice difference too, I don't have 4 GB used at the moment, but I do have more than 2 GB used (a lot of which is cache of course, and another large chunk of which is Firefox).

I read that that problem is solved with the latest firmware update, possibly depending on OS version.

Thought I'd jump in and give everyone a laugh. I'm not upgrading/replacing old hardware with new, I just ordered a monitor for an Inspiron 3500 laptop. Even with 2nd day shipping, it's costing less than what you two are spending. I probably could use a new EIDE hard drive for my desktop.
[edit] I just spent $25 USD for a 160g hard drive. I can't believe they are so cheap.

From my googling, I couldn't positively determine that it would work, so I ordered 6. Most sites said 6 was the max, with "possibly working with firmware update". Played it safe.

I spent $600 on mine and it came with wireless internet and a 10 hour battery life.

Sounds like a shitty netbook, or an iPad (or similar device).

I have my doubts. The only laptop style devices I know of that can last 10 hours are really netbooks (or at least "sub-notebooks"). Like the MacBook Air, or the ThinkPad X series.