Do I need more RAM? You tell me.

G

Gnophos

Registered
In the Classic OS, it was so easy to see when you were getting around to needing a RAM upgrade. Programs would each take up a preset amount of memory, and when they started using so much that you needed to turn on VM, you were in upgrade territory.

Now I am all up-to-date with OS X, since getting my G5 in Oct. '03, but RAM usage eludes me -- let me explain. I have iPulse, which handily gives me the dope on how much RAM and VM are being utilized by each app. Now, my RAM usage never goes past halfway or so, and yet my G5 really seems to choke on VM when I do heavy work, particularly in Photoshop, esp. printing from it (the document being spooled, I guess). I am very sensitive to excessive hard disk activity that indicates VM is being used, from years of having to deal with low memory situations.

So, if I'm not low on real RAM, why does the disk suddenly go through massive read-write operations like it's sending stuff all over the place, when all I'm doing is saving or switching apps? iPulse shows all kinds of stuff happening at times like these. Do such tasks always involve the VM, OR is my Mac calling on VM to supplement the RAM because it would take up too much real RAM???

Oh, I have 768 MB.
 
okay, first thing, os x will use vm, no matter how much ram is installed. i have a g4 with 1.25gig ram, and stats show that the os (10.3.9) has a vm page file over 3gig in size! and i use it mainly for email, surfing, and dvd viewing. second, you said that you notice it most using photoshop, so what do you have ps's memory useage set at? in ps prefs, there is a way to set how much of the ram it uses. of course the higher that is, the more the os uses vm for everything else. so i would say that if you set that down, and notice more of a performance hit, then get more ram. at least a total of 1gig, or add 512 to what you have installed.
macaddict mag did a test of the relation to ram and performace, and found that there is no real gain with more then 1.5-2gig ram. if i remember, the older g5's could handle 4gig ram, but the mag's test showed that there was no difference boosting to 4gig from 2 gig. hope this was some help.
 
Yep: Forget everything you know about RAM from classic Mac OS. Virtual Memory is key. You won't get rid of it - nor would you want to, actually. Photoshop has its own preferences regarding RAM usage and scratch disks, so you might want to look into some optimisation there.
Apart from that: Yes, you need more RAM. You always do. If you can: Get two 1 GB sticks. Or get one and another later. It'll speed up everything.
 
I have a rule of thumb for working out whether more RAM is needed or not.
Just run the computer as you would normally for a couple of days. Don't shut it down, just put it to sleep if you need to. Make sure you do all the normal day-to-day stuff you use the computer for.
Then, go into the Terminal.app and type the command "top".
In the statistics at the top of the display, there will be two values you'll want to look at: pageins and pageouts.

The first value - pageins - is the number of times a program has gone to retrieve something from memory and it has been available in the physical RAM. The second value - pageouts - is the number of times a program has gone to fetch something from memory and has needed to retrieve this from "Virtual Memory" (thats the hard drive).

Pageouts are what slows a computer down.

Next, divide the number of pageouts by pageins, and then multiply by 100. This is the percentage of times the computer needed to hit Virtual Memory for something, as opposed to actual RAM.

If this is more than 50%, you *need* more memory.
If its between about 20-50%, you'll find that more memory will give you a significant boost in performance, but you don't need to go overboard and spend too much money. Just remember that if you double the amount of RAM you have, you'll halve the amount of pageouts, and thus halve the delays caused by pageouts. However going all out and putting in the maximum memory might juts be a waste of money.

If the value you get is less than 10%, it means that pageouts are not causing much delay on your system, which means adding more RAM will not really make much difference. If this is the case, and you want more performance, you'll need to look at other factors.
 
I will have to check that page-out/page-in ratio, and maybe adjust Photoshop; I think it's turned up pretty high in memory usage.

Thanks for the help, guys. I'll probably get another gig, it's only like $100.
 
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