Worth getting more memory?
 

I picked up a decent box to try linux.
Installed Debian lenny.
It's fantastic. Using ratpoison as WM, everything's coming together really nicely (many thanks to those who have been helping me here!). It only seems sluggish (and not surprisingly so) when there are a number of windows open and there's something like the GIMP running.
Since it suddenly looks as if I'll be switching to this as my main system, it might be worth upgrading.
The question is: Would I get a significant performance boost on a machine like this if I specifically chose to increase the memory?
Here's what I have:
Gateway #E-4500D
Pentium 4 300GHz [<-THAT WAS WRONG, OF COURSE - IT'S 3.00GHz, of course!]
1 Gb of memory in the form of 4 256MB DIMM 533MHz sticks
160GB SATA HDD.
Thanks in advance!

Probably. When it feels sluggish, use free and top to see what the system load is. Free will output how the memory is being used, and top will do the same (kind of) plus the supposed CPU load. Whether or not you'll feel that the money is worth the performance increase is another question.

On a similar machine, I found that dumping gnome for fluxbox gave me more satisfactory results than what I would have gotten spending more money on a dead end machine. It's not my primary machine though.

Pentium 4 300GHz,

The problem I see is that system is old. I don't think more ram will pick it up. You might try a lighter window manager before more ram. Might even see about moving swap file to usb flash if it even supports it.

Lighter than ratpoison? Would that be managing windows by hand?

And... if it supports USB? It's not that old! Or am I missing something?

Yeah, I totally missed the part about ratpoison. I would have kept my mouth shut if I'd seen that part.

There is something seriously wrong here. It seems another poster assumed that "300GHz" was a typo for "300MHz", but in that case "Pentium 4" (and 1 GB ram) makes no sense. A 300MHz machine would be at best a P3 and would have far less than 1GB of ram.

Can you confirm what the specs of the machine are?

Evo2.

I thought it might have been "3.00GHz", and the OP just forgot the decimal point; AFAIK there is a specific P4 (a version of the "Northwood" chip if Wikipedia's not deceiving me ;)) that runs at just over 3GHz.

IMHO when playing with photo editting, you can't have too much memory.
You'll have to throw out some of your current chips thought.

That seems to be a safe conclusion. The Gateway #E-4500D has a LGA 775 CPU socket.
http://en.wikipedia.org/wiki/LGA_775

It has 4 ram slots and lists 4GB max ram, which probably means 3.25GB max actually usable. So the plausible ram upgrade is to discard two 256MB ram sticks and purchase two 1GB ram sticks to get 2.5GB total.

At NewEgg, the lowest cost 2x1GB DDR2 SDRAM is $46 plus $3 shipping. (It is DDR2 800, and the Gateway #E-4500D apparently can't use memory at that speed. But DDR2 800 memory works fine when used at a lower speed).

1GB should not be low enough to feel sluggish with many ordinary windows open, assuming you have enough swap space configured that the anonymous memory of the windows in the back won't take priority over the file mappings of the windows in front. So maybe you want to check if you have enough swap space configured.

But doing interesting work in Gimp could certainly get sluggish in just 1GB. If that is what you use the computer for, the upgrade to 2.5GB seems well worth the price (or even slightly more if the lowest cost choice from NewEgg is wrong for some reason).

Yes, you are all right: I lost the decimal point.
3GHz.

Try running vmstat in a terminal session (and ignore the unhelpful first line of output). Let it stabilise for a while. Do something that you think is sluggish.

If the sluggish task is accompanied by evidence of swapping, you'll probably get a speed-up by adding more RAM. If it doesn't, you probably won't.

Only anonymous memory is swapped to the swap partitions (or files). Typically most memory is not anonymous, so swap use is a very bad estimate of how much improvement you might get from more ram. It can also be a bad estimate in the other direction: you might have significant swap use without a situation that would be significantly improved by more ram.

I don't know how to get any accurate measure of whether to expect a significant performance increase from more ram.

I didn't see it mentioned but are you using the onboard GMA950 graphics or do you have a separate vid card? If you use the onboard the extra RAM will help since that's what the chipset uses for VRAM.

Also, it's important to keep in mind that there are two different performance metrics: More RAM, and faster RAM. 2 GB of DDR2-667 will be a further improvement over the same amount of DDR2-533, and that board supports it.

A year ago, I'd have said to just buy the RAM anyway since it was going so cheap, unfortunately that's not currently the case. DDR2-800 is actually cheaper in many instances than DDR2-667 and it will run in that board as johnsfine pointed out, it'll just run at 667 instead of 800. The bonus there is if you upgrade to a board that can use DDR2-800 the investment in RAM is already made.

Only if you replace all the ram.

Assume for the moment that DDR2-800 is less expensive than DDR2-667:

Buy 2 sticks of DDR2-800 and discard all the old ram and the new ram should match (maybe slightly exceed) the ram speed of DDR2-667, so you would have twice as much ram and it would be faster per access.

Buy the same 2 sticks of DDR2-800 and discard only half of the old ram. The resulting ram speed would exactly match the old DDR2-533. So you would have 2.5 times as much ram but individual ram accesses would be no faster.

I can't begin to estimate which of those would result in better overall performance.

Opps times two.