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Dual Processor = Dual Ram?

ITASOR

ITASOR

macrumors 601
Original poster
Mar 20, 2005
4,398
3
Just got off the phone with Apple. They offered me a special deal on free RAM (didn't know they did that), however we got talking about RAM. Here's what he said:

If you have a Dual G5 PM, it's no good to have 2 RAM Cards that are different, ie. 512MB + 1GB, especially if they are different brand. He says you need to put in 2 identical cards or you will have major problems using the computer.

I've never heard the dual ram part, but I've heard the same brands part.

Is this really true or was he trying to get me to buy more RAM?

Thanks.
 
Same problem with Powerbook?

I just got a powerbook a few weeks ago and purchased a 1 gig stick of ram to supplement what I already have (a 512 stick). Will I have any problems?
 
I don't think so because it doesn't have a dual processor.



So if I buy a PM from MacConnection and they offer the 1GB free, they said they just put a 1GB card in. I told them all this and they said that it doesn't matter. I guess the 512MB that comes in the G5 is 2 256MB cards, correct? To get the 1GB, could you just install 2 more 256 cards or take them out and install 2 512MB cards.

If anyone knows, why do they have to be in pairs?
 
Not so much

1. Its better that they be in pairs you get a speed boost when ram is paired two 256 sticks is faster than one 512 stick but you lose this compatability advantage when you mix say a 512 and a 256. (paired ram has a speed boost unpaired does not)

2. Sometimes you encounter problems im not really certain what causes the problems, a friend of mine bought a 1gig stick to plug in his imac and when he did the thing went haywire, he returned the stick got a different brand and it worked computers are finicky even macs.
 
I am going to order a 2.3 dual. Can I just leave in the 2x512 sticks that come with it, and order 2 1gb sticks from crucial? or would i have to take the 512's out?
 
GoldenHoya said:
I just got a powerbook a few weeks ago and purchased a 1 gig stick of ram to supplement what I already have (a 512 stick). Will I have any problems?
Click to expand...

No you will not. The only machine that needs to have pairs is the PM. Assuming the RAM is compatible, you shouldn't have any problems.
 
The PM requires RAM to be installed in pairs because it used Dual-Channel memory. Here are other requirements:
DIMMs must be installed in pairs
Both DIMMs must use the same density memory chips
Both DIMMs must use the same DRAM bus width
Both DIMMs must be either single-sided or dual-sided
Click to expand...
taken from PCTechGuide
 
It doesn't have anything to do with the number of processors. The single processor PowerMacs are the same way. (Albeit with less slots) Besides having 8 memory slots and needing to have them paired is really to your advantage. Why would you buy a 1 GB stick when you can get 2 512 MB sticks for less? I wish I could have done that with my iBook. :)

Also, it sounds like this guy has dealt with Dell salespeople, the way he distrusted the Apple one. ;)
 
lazyboy922 said:
I am going to order a 2.3 dual. Can I just leave in the 2x512 sticks that come with it, and order 2 1gb sticks from crucial? or would i have to take the 512's out?
Click to expand...

Removing the 512's will not be necessary.
 
AP_piano295 said:
1. Its better that they be in pairs you get a speed boost when ram is paired two 256 sticks is faster than one 512 stick but you lose this compatability advantage when you mix say a 512 and a 256. (paired ram has a speed boost unpaired does not)
Click to expand...

If you're talking about Powermac G5's then you're very wrong. Powermac G5's REQUIRE the same RAM, installed in pairs. Other Apple computers do not require installation in pairs. A Powermac G5 being dual processor has nothing to do with having to pair RAM.
 
Blackheart said:
If you're talking about Powermac G5's then you're very wrong. Powermac G5's REQUIRE the same RAM, installed in pairs. Other Apple computers do not require installation in pairs. A Powermac G5 being dual processor has nothing to do with having to pair RAM.
Click to expand...
Except you have all ignored the fact that the G5 iMacs, although they don't *require* matched memory, get a nice speed boost when two matched memory sticks are used (64 bit memory access (1 stick or non-matched) vs 128 bit memory access (2 matched sticks)). I know, since I have (my wife has) said iMac, and we ran it both ways; the matched memory makes a big difference. I also have a dual 2.5 GHz G5; memory must be added in matched pairs.
 
daveL said:
Except you have all ignored the fact that the G5 iMacs, although they don't *require* matched memory, get a nice speed boost when two matched memory sticks are used (64 bit memory access (1 stick or non-matched) vs 128 bit memory access (2 matched sticks)). I know, since I have (my wife has) said iMac, and we ran it both ways; the matched memory makes a big difference. I also have a dual 2.5 GHz G5; memory must be added in matched pairs.
Click to expand...

I didn't ignore it at all; I explicitly stated that the following facts were for Powermac G5's.

EDIT: Also, the original poster's question was regarding Powermacs.
 
Now, the G5 iMac gets a boost with paired RAM...

Is this also true of G4 and G3's? I've always wondered if it helps the computer address the RAM any faster.
 
The PowerMac G5's, xServe G5's and iMac G5's (along with most hi-end PC's) support dual channel RAM, which means if you install matched pairs you get twice the bandwith speed you had before. AKA DDR400 RAM (PC3200 used in G5's) runs at 400Mhz installed by it's self, but installed in pairs runs at 800Mhz. BIG Difference. The iMac G5's allow this as an option, it is better to put 1Gb (2x512 matched) than 1.5Gb(512 & 1Gb not matched) in that machine. PowerMac G5's and xServes' memory controller requires Dual Channel because apple realizes the performance boost, and the whole 128bit memory or whatever...whatever that someone brought up above. I was just talking about Dual Channel
 
zach said:
Now, the G5 iMac gets a boost with paired RAM...

Is this also true of G4 and G3's? I've always wondered if it helps the computer address the RAM any faster.
Click to expand...
No, because they only have a 66-167MHz FSB (Front Side Bus). The G5s in the PowerMacs have higher FSBs, half the CPU speed, so they need the higher dual channel RAM (2x 400MHz). The iMac doesn't need it, because it's FSB is lower. 1/3 the CPU speed. You can run single sticks, or mis-matched pairs, but it will run in dual channel (128-bit) if you install a matched pair (2 of exactly the same sticks of RAM, size and speed), so you get a bit of a performance gain. The G3/4s don't have that option, and their FSBs are too low to get much of a gain anyway.
 
Blackheart said:
I didn't ignore it at all; I explicitly stated that the following facts were for Powermac G5's.

EDIT: Also, the original poster's question was regarding Powermacs.
Click to expand...
My point was that paired memory isn't limited to G5 PMs. There just might be a G5 iMac owner or two reading the thread, too. Is that OK with you? Thanks.
 
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