Buying RAM

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This guide is meant to provide information about places to buy RAM for your Mac. For installing your newly bought RAM see the Installing RAM guide. Then complete your journey by testing your new RAM, following the Testing RAM guide.

Contents

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What to Buy

Example memory info in System Profiler
Enlarge
Example memory info in System Profiler

Before you purchase memory, you need to know what kind to get. The easiest way to figure this out is to look in the manual that came with your Mac. There will be a section on memory upgrades, advising you exactly what type and speed of memory it needs. You can also check the System Profiler utility: go to the Apple Menu, About This Mac, More Info..., then click on Memory.

Key things to know are:

  • Speed: sometimes expressed in MHz, but often as a "PCnnn" number where nnn can be a number like 100, 133, 2700, 3200, 4200, 5300, or many others.
    • The numbers are equivalent:
    • PC2700 is the same as DDR-333 MHz
    • PC3200 is the same as DDR-400 MHz
    • PC2-4300 is the same as DDR2-533 MHz
    • PC2-5300 and PC2-5400 are the same as DDR2-667 MHz
  • Type: here you'll see any number of acronyms, including SDRAM, DDR, DDR2, FB-DIMM, and more. You cannot substitute one type for another -- DDR2 is not backwards compatible with DDR for example. There's also ECC (error correcting RAM), which can be installed in recent Power Macs, Mac Pros, and Xserves. Really old systems may even have FPM or EDO RAM.
  • Format: You will usually see DIMM (desktop full sized modules), or SO-DIMM ('notebook' size modules, however all of the Mac Core/Core2Duo machines use SO-DIMMs)
  • Pins: different physical sizes of memory chips usually have different numbers of pins. Common numbers for current machines are 184 pins, 200 pins and 240 pins.
  • CAS Latency: this one isn't quite as important; the right type and speed of memory should work even if the CAS number is slower. Adding memory with faster CAS than your machine supports won't speed anything up, and adding memory with a slower CAS will probably only be a small percentage slower.
  • Dual Channel: many Apple machines use dual channel memory. In a few cases, this means that memory must be installed in matched pairs. Your computer's manual would say so if that's true. For the majority of cases, unpaired chips will work fine, but matched pairs will result in a slight speed increase (on the order of a few percent).
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Quality and Pricing

Apple's prices for RAM and hard drives are outrageously high. Remember, Apple loves profit, not you. Whenever you can buy your Mac with the stock RAM, and upgrade later with third party RAM from a reputable supplier. Apple buys Samsung, Hynix and Micron RAM modules in bulk, just like good third party brands do, there is nothing special about Apple branded memory.

When buying memory, it is generally not advisable to go with the absolute cheapest stuff you can find. Many Mac models have a reputation for being very picky about the quality of RAM they will work with. Low quality memory can and often will cause application crashes, total machine crashes, and data corruption. Do your homework on quality reputation up front, and be advised that while buying generic memory saves you money, you assume a greater risk of trouble later on.

You may also have issues if you use High Density RAM in your Mac (this is the most common form of RAM that can be purchased from eBay). You may find it simply doesn't work with your Mac, the computer only accepts half the amount or it runs much slower. RAM bought from a recommended supplier will not be high density and will work correctly.

It is not recommended to buy RAM faster than your machine will handle. It won't make the machine run any faster (the Mac sets the memory bus speed, not the RAM module), and there may be compatibility issues with the RAM clocking down to the Mac's bus speed. 800 MHz SODIMMs are widely reported to be incompatible with Penryn Core2Duo Macs, which require 667 MHz memory.

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Where to Buy

  • Crucial - good place to buy RAM from all over over the world. They also have an excellent memory selector that allows you to choose memory based on your computer's model, rather than having to remember terms like PC133, PC3200, PC5300, 184-pin, 200-pin, DIMM, and SO-DIMM. Guarantees compatiblity and quality. Make sure to refresh the page a couple of times before you buy and clear your cookies as crucial uses different prices based on the operating system and browser being used (just to be sure, check the prices with different browsers like Safari, Camino, Firefox). Crucial's prices are variable - while they have a stellar quality reputation, you may consider looking elsewhere for a better deal.
  • MemoryAmerica - good competively priced RAM, ships internationally and guaranteed compatibility.
  • NewEgg and Fry's-Outpost- are discount resellers of Crucial and other generic RAM, if you live in the U.S. Beware though that they usually do not guarantee compatibility. Some discounters have a 15% restocking fee policy for returns. Only for experienced buyers.
  • TransIntl - competitively priced RAM easily matched to your specific computer
  • MacRAM Direct - competitively priced RAM. Certified Apple Ram as well. Easy to navigate website.
  • In the UK, Crucial has a UK store, OWC will ship overseas (at the buyer's expense and risk) and there are some UK based companies such as Orca.
  • In Canada, CanadaRAM offers good prices on RAM and customer service on RAM that has been tested in and guaranteed to work in Macs.
  • Independent Authorized Apple Resellers can provide and install RAM for most models. As they are resellers they do not need to order RAM from Apple therefore offer much more reasonable prices and can guarantee compatibility. Apple Stores themselves generally will not install any RAM not purchased from Apple.
  • There is always the possibility of course to get your RAM at the Apple Store when you buy your new Mac and have them install it as well as confirm it working. For people that don't care about the price and/or don't want to install the RAM themselves this might be an option. But be aware that you can get comparable, equally compatible RAMs for a much lower price.
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Caveats

  • Check the type of RAM you need before ordering. Best is to buy from a seller who offers a compatibility list or an online configurator that identifies the correct RAM part number for your Mac.
  • eBay and other auctions are a risky place to buy RAM. Besides the normal risks of outright scams and frauds like used instead of new, non-functioning, or not as described items, there is a % of counterfeit RAM on the market, especially in flash memory cards for cameras and phones. It has been estimated that 90% of the SanDisk flash memory on eBay are forgeries. RAM that has been pulled from machines (such as the RAM that comes out of an Apple when you upgrade) has no warranty. Getting refund / repair / warranty service from an eBay vendor is considerably riskier than from an established vendor with a physical location.
  • International purchases: When purchasing from outside your country, while the seller may advertise "no taxes or extra charges" you are almost certainly going to be charged for some or all of: VAT/GST/local tax, duties, customs brokerage fees, and/or advancement fees when the package arrives in your country. UPS Ground courier is notorious for charging low shipping costs but sky-high brokerage costs. These fees can substantially increase the cost of your purchase. Air freight is expensive, but often includes the customs brokerage, so it may be a wash against the cost of ground + brokerage. The least expansive way to import goods is through normal postal parcel mail. Unfortunately, that is also the method that is most prone to loss or theft. Always insist on a shipping method that includes insurance and a tracking number.
  • In addition, if there is any warranty issue with your internationally purchased RAM, you can expect to pay shipping costs and customs clearing costs both ways, which can be expensive.
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Warranties

It is always recommended that where ever you purchase RAM from, you check their warranty and returns policies. Many cheaper suppliers only give you a 1 year warranty and will not accept returned RAM unless it's faulty. RAM, after being removed and reinserted a number of times, may have the connections wear down. Thus the lifetime warranty, or a 5-year warranty, may come in handy. Check to see whether warranty is handled by the seller, or whether they force you to deal with the manufacturer for warranty replacement (this is a problem with manufacturers like Samsung who do not sell retail and will refuse to deal with you as an end user).

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Will it make my machine faster?

Taking your foot off the brake does not make your car go faster - it just discontinues slowing it down.

Increasing the memory in the Mac does not increase the Mac's speed -- rather it removes slowdowns that result from your programs and data not having enough memory. When there isn't enough memory for all you are doing, OSX is forced to swap memory space on and off the hard drive. Because hard drives are much slower than RAM, this slows the machine down overall.

How much your machine slows down depends on how you are using it. If you use just one program at a time, and don't open large data sets, then you may not notice a speed difference with more RAM. If you regularly multitask many programs, or use 'hungry' programs (like Photoshop, virtualization (Parallels, VMWare), digital video or digital audio software), then you should see noticeable improvement with 3 GB or 4 GB RAM.

When you are running multiple programs at once, more RAM makes switching from one program to another faster, because Mac OS X can cache the previous program's memory in 'inactive' memory for a longer time before it has to get flushed out to make room.

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When it Arrives

Move on to Installing RAM and then Testing RAM. Enjoy!

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Which RAM to Buy

First step is to order from a reputable dealer who guarantees compatibility with your model Mac, so you don't have to know which specific modules to order.

You can also look up the correct modules at the better vendors' websites, which have configurators such as Data Memory Systems, Kingston and Crucial (one thing, Crucial sometimes recommends premium RAM that is faster than the particular Mac can take advantage of. It will work, but the extra expense is wasted)

Here is a partial summary of Mac models.

Notes: In some cases older machines are 'officially' specified for slower modules, but compatible faster modules are commonly substituted - PC2700 for PC2100, or PC133 for PC100. The more common permissible faster modules are quoted below. Also note that "PC133" or "PC2700" is not a complete description of a memory module, and there are multiple other factors that determine compatibility. For example you can't assume that every PC133 memory module will work in a Mac that takes PC133.

eMac G4

700 MHz, 800 MHz, 1 GHz USB 1.1 model only: PC133 DIMMs, 2 slots, max. 1 GB (2 x 512 MB)

1.0, 1.25, 1.42 GHz USB 2.0 models: PC2700 DDR (333 MHz) DIMMs, 2 slots, max. 2 GB (2 x 1 GB)


iMac G3

233, 266, 333 MHz with Tray-load CD: PC66 SODIMMs, 2 slots, max. 512 MB (2 x 256 MB) although some early machines can't recognize more than 384 Mb.

300, 350 MHz, and up with Slot-Load CD: PC133 DIMMs, 2 slots, max. 1 GB (2 x 512 MB)


iMac G4

These machines have 2 memory sockets in 2 different formats. The user-accessible slot is a SODIMM (laptop size), the internal memory is a DIMM and should only be accessed by someone with the correct instructions for disassembly of the machine out of the 'dome'. You can damage the machine if you don't know what you are doing inside.

700 Mhz, 800 MHz: 1 x PC133 SODIMM and 1 x PC133 DIMM, 2 slots, max. 1 GB (2 x 512 MB)

1.0 GHz and 1.25 GHz : 1 x PC2700 DDR (333 MHz) SODIMM and 1 x PC2700 DIMM, 2 slots, max. 2 GB (2 x 1 GB)


iBook

G3 'Clamshell' and G3 'White': PC133 SODIMM, 1 slot, maximum 640 MB (1 x 512 MB + 128 MB built-in)

G4 12" and 14": PC2700 SODIMM, 1 slot, maximum 1.25 or 1.5 GB (1 x 1 Gb + 256 MB or 512 MB built-in)


iMac G5

1.6, 1.8 and 2.0 GHz: PC3200 DDR (400 MHz) DIMMs, 2 slots, max. 2 GB (2 x 1 GB) (These machines are very sensitive to out of spec RAM - generic PC DIMMs are not recommended)

1.9 and 2.1 GHz 'iSight" model: PC2-4200 DDR2-533 MHz DIMMs, 1 slot, max. 2.5 GB (1 x 2 GB + built-in 512 MB)


Intel CoreDuo / Core2Duo / Core i5 / Core i7 machines:

  • All models until April 2008: DDR2-667 MHz (PC2-5300 or PC2-5400) SODIMMs, two slots.
  • The 21.5' and 27' iMacs released in October 2009 have four slots.

Maximum RAM varies with the chipset used, see Understanding Intel Mac RAM for detail.

There have been many reports of 800 MHz SODIMMs failing to work in the Penryn Core2Duo MacBook Pros. There is no speed advantage to buying 'faster' clocked RAM, so stick with the 667 MHz for compatibility.

iMacs released between April 2008 and February 2009 use DDR2-800 MHz (PC2-6400) SODIMMs.

iMacs released in March 2009 and October 2009 use DDR3-1066 Mhz (PC3-8500) 204-pin SODIMMs.

Exceptions

  • MacBook Air: no memory expansion, 2 GB is built in


MacPro

2007 model Xeon: 667 MHz ECC Fully-Buffered DIMMs (FB-DIMMs), normal DDR2 modules are NOT compatible.

Jan 2008 model "Penryn": 800 MHz ECC Fully-Buffered DIMMs (FB-DIMMs), the 667 MHz FB-DIMMs from the earlier MacPro are NOT compatible.

Do not install FB-DIMMs sold for PC server machines. Choose only Mac-compatible FB-DIMMs


Mini G4: PC2700 DDR (333 MHz) DIMM, 1 slot, max. 1 Gb (1 x 1 GB) (These machines are very sensitive to out of spec RAM - generic PC DIMMs are not recommended)


Powerbook G4

"Titanium" models (400 MHz - 1 GHz): PC133 SODIMMs, 2 slots, max. 1 GB (2 x 512 MB)

"Aluminum" 12" models (867 MHz - 1.5 GHz): PC2700 DDR (333 MHz) SODIMM, 1 slot, max. 1.25 GB (1 x 1 GB + built in 256)

"Aluminum" 15" and 17" screen models (1.0 GHz - 1.67 GHz pre-October 2005): PC2700 DDR (333 MHz) SODIMM, 2 slots, max. 2 GB (2 x 1 GB)

  • Note: The 1.0 GHz 15" and 17", the 1.25 GHz 15" and the 1.33 GHz 17" require special processor-slewing compatible modules; common PC2700 SODIMMs will not work. Choose a seller who knows the difference and offers RAM that is specifically compatible with your model Powerbook.

"Aluminum" 15" and 17" 1.67 GHz models (HD Screen / DL Superdrive models introduced Oct. 19 2005): PC2-4200 DDR2-533 MHz SODIMMs, 2 slots, max. 2 GB (2 x 1 GB)


PowerMac G3

Blue and White G3 tower, "Yosemite" motherboard 256 MB PC100 DIMMs, requires low density modules, max 1 GB with 4 x 256 MB. These machines will not use 512 MB DIMMs

Beige G3 desktop and mini tower, 256 MB PC66 DIMMs, requires low density modules, max 768 MB with 3 x 256 MB. These machines will not use 512 MB DIMMs. Desktop models require low profile modules.


PowerMac G4

G4 PCI Graphics "Yikes" motherboard 300, 350, 400 MHz: PC100 DIMMs, 4 slots, max 1 GB with 4 x 256 MB low density DIMMs. These machines will not use 512 MB DIMMs

G4 AGP graphics "Sawtooth", Graphite, Gigahertz, Power2Burn and Quicksilver models: PC133 DIMMs 3 or 4 slots, max 1.5 GB with 3 x 512 MB DIMMs.

G4 Mirror Drive Door models: PC2700 DIMMs, 4 slots, max 2 Gb with 4 x 512 MB DIMMs. (It has been reported that 2 x 1 GB DIMMs could be used, but the other 2 sockets then have to be left empty, this is not recommended)


PowerMac G5

Single and Dual-Processor PCI/PCIX bus machines prior to Oct. 19 2005: PC3200 DDR (400 MHz) DIMMs, 4 or 8 slots, max. 4 GB or 8 GB (4 or 8 x 1GB)

Dual-core PCI-e bus machines (introduced Oct 19 2005): PC2-4200 DDR2-533 MHz DIMMs, 4 slots, max. 16 GB (4 x 2GB)

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Crucial Memory Scanner

Crucial, a subsidiary or Micron Technology, has released a tool for Mac users running Mac OS called Crucial Memory Scanner. Once downloaded the tool can scan your system for its version and hardware base. The scanner will then take you back to its parent site where you can view and purchase from a list of RAM packages supported by your Mac. An obvious drawback is that the tool will only report back with packages manufactured and sold by Crucial.

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