[FAQ] - RAM Specs

themacko

Barking at the moon.
Hopefully this little FAQ will help you better understand what kind of ram is right for you. Some people say that "ram is ram is ram" which is not necessarily true. Especially if you are a power user and want the biggest and the best.

Anyhoo, I hope this helps. If you have any questions, feel free to ask me. (sending me a PM is probably the best way to reach me on the forums)

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What is ram?
Ram is actually and acronym for random access memory. It is the memory that programs are able to use when they run. The more ram you have, the more memory your applications have and in turn, the faster your system and programs will run. The terms ram and memory are used interchangably.

Will PC ram work in my Mac?
Yes. If you have a PC with 128 MB of PC133 ram and want to put it in a Mac that uses 133mhz ram, it will work. It's generally the same stuff.

How much ram should I have in my Mac?
This is a system/user specific question, but generally speaking, 256mb would be plenty for the average user. Apple recommends at least 128mb in OS X, which actually works fine. But the bigger and more graphic-intensive your everyday programs are, the more ram you should have.

What speed memory should I get?
The three speeds of ram used in Apple computers are PC66, PC100 and PC133. You can find out what speed you need by checking your owner's manual or going to Applications > Utilities > Apple System Profiler and then find the Memory Overview section. It will tell you how much and what kind of memory your computer currently has.

The PC number is the speed of the ram, in megahertz (mhz). The newer Power Macs and iMacs use 133mhz ram, or PC133. The newer iBooks use PC100. You can run faster ram at lower speeds, but you can cannot use, for example, PC66 ram in a machine that requires PC100. It's generally not a good idea to mix and match your ram types and speeds, but if necessary it can be done.

What is the difference between CL=3 and CL=2 ?
CL stands for "CAS latency," which is a number that refers to the ratio - rounded to the next higher whole number - between column access time and the clock cycle time. It is derived from dividing the column access time by the clock frequency, and raising the result to the next whole number.

CL2 parts process data a little quicker than CL3 parts in that you have to wait one less clock cycle for the initial data. However, after the first piece of data is processed, the rest of the data is processed at equal speeds. Latency only affects the initial burst of data. Once data starts flowing, there is no effect. Bear in mind, a clock cycle for a PC100 module is 10 nanoseconds so you probably won't notice a significant performance difference.

Do I need error-checking?
When choosing among ECC, parity, and non-parity memory, you need to match what is already in your system. You can tell which kind you have by looking at one of the modules currently in your system. Count the number of black chips on one module. If the number of chips can be evenly divided by three or five, you should buy ECC or parity (whichever is offered for your system). If not, you should buy non-parity.

For example, if one of your modules has nine chips, you should buy ECC or parity. If one of your modules has eight chips, you should buy non-parity. In our newer Macs, non-parity is what you're looking for and pretty much all they offer.
 

Mikuro

Crotchety UI Nitpicker
Just for the record, the original post was made in 2001, and is now outdated. Here are a couple quick updates:

1. Apple now recommends 256MB of RAM as the practical minimum. Most people generally recommend 512MB.

2. No current Macs use PC66, PC100 or PC133 RAM anymore. They all use PC2700 (AKA DDR333) or PC3200 (AKA DDR400). "DDR" stands for Double Data Rate; without going into the techie details, let's just say it's faster than old PC133 RAM, and is NOT backwards compatible (e.g., whereas you could use PC133 RAM in a PC100 system, you cannot use PC2700/3200 in a PC133 system).
 

[-Stash-]

Registered
I can tell you for certain that Tiger, uhm, how can I put this gently, "blows chunks" when I have more than 1 app open at a time on 256MB RAM. That and you can't even INSTALL Photoshop CS2 with less than 384MB RAM. My GF's 500MHz G3 iBook feels faster running Panther because it has 640MB RAM in it. I wouldn't go for anything less than 512MB as an absolute minimum any more. Exactly the same as WindowsXP.
 

Jim W

Registered
I just upgraded my 2 month old G5 from 512 to 2 gig. I have been monitoring the pageouts (thanks to someone here for recommending the 'top' command--can't recall who) and it has been in excess of 60% and I really don't do anything too taxing with it, so far.

I have had the 2 gig in for 2 days now and do not have 1 single pageout, yet.
 

Heavywear

Registered
Jim W said:
I just upgraded my 2 month old G5 from 512 to 2 gig. I have been monitoring the pageouts (thanks to someone here for recommending the 'top' command--can't recall who) and it has been in excess of 60% and I really don't do anything too taxing with it, so far.

I have had the 2 gig in for 2 days now and do not have 1 single pageout, yet.
I'll be doing the same upgrade here shortly Jim. Any RAM brand recommendations or does it matter? I was going to go with MacConnection or MacSales
 

fryke

Moderator
Staff member
Mod
Those are stores, not brands, though. Kingston, I hear, is good, albeit a bit more expensive.
 

Porce

Registered
I bought an iBook back when they still shipped with 256 MB RAM and it's pretty pathetic. I've got Firefox, iTunes, Mail, and Adium open all day usually. If I want to open something memory-intensive I'll usually have to close Firefox and maybe another program unless I want to deal with pretty bad lagging and such.
 

Lt Major Burns

"Dicky" Charlteston-Burns
i'm waiting for 1gb to drop below £50, then i'll double mine
 
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