MacBook RAM question

Bloke · 2011-09-01 22:03:12

Since I know a lot of clever people here use Macs I thought I’d try my luck with a non-Txp question here, rather than register and post on an official Apple forum to get flamed for being too stupid.

The HDD in my wife’s MacBook (original model from mid-2006 with just the old 1.83GHz Core Duo) coughed and died. Gonna replace it with a WD Scorpio Blue, but while I was at it I thought I’d upgrade the RAM ‘cos the stock 512Mb (2 × 256Mb) is awfully small. I’m interested in running Snow Leopard because of the speed optimisations and I know it can run because I’ve had it running via Target Disk as an experiment; it just won’t let me install it without 1Gb minimum. She’s only browsing and running Office + iTunes most of the time, but it does grind a bit at the simplest of tasks.

Anyway, all the specs say 2Gb is the max addressable RAM on these old models, but info on various forums I’ve found points to the fact that sometimes you can address more. Trouble is, few people can agree on what is and isn’t the truth (this is the closest I’ve found to a definitive guide).

I have a choice between getting:

a matched pair of 2 × 1Gb sticks
a single 2Gb stick

Option (1) of course gives 2Gb in total and no expansion options, bar replacing the lot. Option (2) could potentially give me 2Gb + 256Mb if I left one of the old sticks in; possibly more if the chipset can actually address more than Apple’s specs state and I find a 1Gb or 2Gb stick down the back of the sofa at a later date.

Question: Is it worth losing the advantage of matched RAM for a measly (theoretical) gain of 256Mb and the uncertainty of the OS even seeing it, or being able to upgrade further in future? Is it even advisable to leave one of the old sticks in (the guide above implies it’s ok) or — if I went for option (2) — should I just use one of the slots and leave the other one empty?

Sorry if this is noob territory. If I was building a PC I’d stick with matched RAM (despite the fact it’s more expensive) and to hell with the old sticks, but with Apple being Apple I just wanted to check if the same holds true, or whether I’m going to cause unneccesary strain on the ageing hardware by using mismatched RAM or leaving an empty slot. Thanks in advance.

Last edited by Bloke (2011-09-01 22:48:13)

ruud · 2011-09-01 22:24:00

benchmarks matched/unmatched

Generally speaking: matched memory is faster if you’re making heavy use of onboard graphics (at least a GPU that uses part of your RAM). For most other things the difference can be measured, but is not that big. If you can choose between more RAM and matched RAM, choose more RAM.

Another option is just buying a single stick of 1GB RAM and combining that with the 256MB you already have.
For option 2, see here

The price difference isn’t that big between 1×2GB or 2×1GB
Crucial recommends using 2×1GB, claiming the maximum per slot is 1GB.

PS. I don’t have nor use a Mac.

Last edited by ruud (2011-09-01 22:36:15)

Bloke · 2011-09-01 22:46:35

ruud wrote:

If you can choose between more RAM and matched RAM, choose more RAM.

I’ll remember that in future when it comes to upgrading my PC then, thanks. Though I do a lot of audio and graphics / video work so that might skew things a bit.

And thanks for the ‘woes’ link. Most of the other places I found said you could put more in, but it just wouldn’t address it (at least for the newer model Macs). That thread seems to imply the older MacBooks simply give up if you try to break the limit.

Crucial recommends using 2×1GB, claiming the maximum per slot is 1GB.

Ah, I hadn’t considered there might be a limit per slot (pretty naive of me). That’s valuable insight, many thanks.

Looks like it’s either a single 1Gb + an existing 256Mb stick or 2×1Gb, depending on how much is in my wallet right now. Awesome info, thanks.

colak · 2011-09-02 05:24:18

Looks like it’s either a single 1Gb + an existing 256Mb stick or 2×1Gb, depending on how much is in my wallet right now. Awesome info, thanks.

I might have it wrong, but it has always been recommended to me to have 2x the same RAM as macs prefer that.

jakob · 2011-09-02 07:45:45

Crucial seem to suggest that there is 1GB max per slot with best performance from matched modules.

I have a Core Duo Macbook Pro from the same time and that has the same 2 × 1 GB limit. Snow Leopard works fine, but Lion only works on a Core 2 Duo upwards.

Last edited by jakob (2011-09-02 07:46:38)

maniqui · 2011-09-02 13:19:35

(Mac illiterate here).

If by matched RAM you mean not only size, but also speed & brand, I can comment that, recently, I was diagnosing a friend’s new high-end Asus laptop because of slow performance, and visual glitches/artifacts. At first, I’d have blame Win7 to being with, but then found out that it was using 2×2GB sticks that didn’t match brand & speed.

Then, I tested both sticks together, booting a LiveUSB of some Linux flavor (Ubuntu & LMDE), and being that LiveUSB systems are loaded on RAM, I thought this could be a good way to do a quick testing. I recall having hard freezes on Ubuntu, and also, some nasty errors were printed directly to the console. This seemed directly related to RAM issues (bad sticks or non-matching sticks?).

Finally, after long-run testings with memtest and confirming sticks were OK, I tested sticks individually (by just running the OS during a while) and performance was better (even being that it was running on half the amount of RAM) and visual glitches went away. Both sticks seemed to perform fine individually.

So, although my tests weren’t scientifically accurate nor conclusive, my opinion is: non-matched speed/brand sticks may give you some headaches.
Also, I understand that you don’t take advantage of dual-channel capabilities if using sticks with unmatched size.

Bloke · 2011-09-02 13:40:22

Thanks for the further info chaps. Based on all the feedback here I’ve gone with 2 × 1Gb sticks from Crucial.

@jakob: yeah I was almost tempted to try Lion until I checked the System Requirements and spotted the sneaky ‘2’ in the CPU name. Shame.

And thanks for the story maniqui. I know the industry “recommend” matched RAM but I always thought it was a sales gimmick (the same way battery manufacturers always recommend that you never mix batteries from different suppliers in the same device, which always seemed a bit silly to me). Good to know there might be some truth in the RAM matching recommendations.

Must admit I’ve had weird things happen — non-booting, POST beeps, crashes and such like — when filling up DIMM slots on PCs before with old RAM I found in the drawer, but I always assumed it was because the RAM speed / type was simply unsupported by the motherboard. Most anecdotal evidence points to the fact that the bus should scale back to run at the speed of the lowest spec chip, but in practice it seems there’s more to it than that, especially now in DDR2/DDR3 land.

I don’t know if the MacBook Core Duo’s slots are actually dual-channel or not. I guess they would be.

Last edited by Bloke (2011-09-02 13:41:57)

Gocom · 2011-09-02 16:06:21

Bloke wrote:

@jakob: yeah I was almost tempted to try Lion until I checked the System Requirements and spotted the sneaky ‘2’ in the CPU name. Shame.

Yep, Lion being only 64-bit (as in x86-64) requires x64 processor, which Core Duos aren’t. Lion removed x86 support and also, long due, PowerPC emulator.

But even if the machine where able to run the OS (if hypothetically speaking Apple hadn’t removed the layer or the MackBook used equivalent C2D), it likely wouldn’t provide any additional performance optimization at least. Wasn’t really release directed to optimizations, but more to features.

Even that I purchased Lion I don’t personally see it as must have update. New full screen API is nice, new scroll API is nice too and removed deprecated features are plus (as they weren’t maintained), but the features don’t really even seem truly finished, and none seem helpful to me. Flipped scrolling direction made me giggle tho. Maybe it’s like they say, that we humans just hate change.

ruud wrote:

PS. I don’t have nor use a Mac.

maniqui wrote:

(Mac illiterate here).

/me balances statistics. Posting this from one even.

Last edited by Gocom (2011-09-02 16:10:08)

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#1 2011-09-01 22:03:12

MacBook RAM question

#2 2011-09-01 22:24:00

Re: MacBook RAM question

#3 2011-09-01 22:46:35

Re: MacBook RAM question

#4 2011-09-02 05:24:18

Re: MacBook RAM question

#5 2011-09-02 07:45:45

Re: MacBook RAM question

#6 2011-09-02 13:19:35

Re: MacBook RAM question

#7 2011-09-02 13:40:22

Re: MacBook RAM question

#8 2011-09-02 16:06:21

Re: MacBook RAM question

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