Mac Tales

PC2-5300? PC2-5400? Corsair? Crucial? Apple own brand? WTF?

I recently decided to upgrade the memory in my Macbook; I learned a few valuable lessons along the way, which today I’m going to share…

Background

When I originally purchased my second generation (Core 2 Duo) Macbook, I decided not to buy additional memory for two reasons.

Firstly, this was my first Mac; my experience of Linux suggested that I wouldn’t necessarily need the same amount of RAM that an equivalent windoze PC would require for similar performance.

Secondly, I noticed while configuring a new Macbook on the Apple store, the cost to upgrade from the standard 512MB, to 1GB is much more expensive than the cost of a third party 1GB memory kit.

Macbook memory modules

Macbooks have two slots for DDR2 677MHz SODIMM memory modules; also known as PC2-5300.

Note: PC2-5300 is the correct name for modules that conform to DDR2-667 specification. Some manufacturers have opted to call their modules PC2-5400, the reason for this appears to be nothing more than windoze over-clocking culture; some claim they have tested their memory to a higher clock speed.
To all intents and purposes, PC2-5400 is the same as PC2-5300.

Dual Channel

When the Macbooks memory slots are populated with identical pairs of SODIMM modules, the Macbook will attempt to operate in Dual Channel mode. Dual Channel mode may provide a marginal overall speed improvement, perhaps up to 10% in some cases.
The risk is this; if the modules haven’t been properly matched (in every possible way – not just the specs you read on the box) then the computer may not operate correctly; you may end up with a spontaneously rebooting Mac.

In order to avoid this, you should avoid using two, apparently same memory modules that weren’t sold by the manufacturer as a matched pair.

Mix and Match

Using different sizes of memory is OK. You will sacrifice Dual Channel, but this is probably not a big deal. The speed improvement from adding memory is way bigger than the speed improvement provided by Dual Channel alone.

For example, let’s say, like me, you currently have a matched pair of 256MB sticks.

Let’s say I have two options, I can either,
a) Buy a matched pair of 512MB SODIMMS, resulting in a total memory capacity of 1GB, or
b) Buy a single 1GB SODIMM stick, replacing one of my existing sticks, resulting in a total memory capacity of 1.25GB.

Under most circumstances, option b) will offer the most benefit.

The performance improvement of an additional 25% memory is nearly always greater than that of having a matched pair, and Dual Channel.

What to do?

At the time of writing, a 2GB kit (the maximum my Macbook will address) is available from Apple for $440 AU.

My favorite local computer store will sell me a Corsair 1GB PC5400 SODIMM for $36 AUD. Wow!

Corsair have a memory configuration utility which lists my Macbook as compatible with this memory – however a bit of Googling reveals that since there is no pair-matching, buying two of these particular SODIMMS is risky (there are reports of random reboots).

I suspect if I only wanted one (keeping one of my 256MB sticks), they would be fine.

So I did a bit more research, and found that one of Apples own memory suppliers is also my favourite: Crucial.

So, I have ordered a matching-pair (2x 1GB), for a grand total of $75 including UPS shipping (from the US) to Australia.

At those prices – why wouldn’t I upgrade!

Available directly from Crucial.com