The new, dual USB iBooks are capable of supporting up to 640 MB of RAM, except the CD-ROM model which tops out at 576 MB. That limit is reached by adding the largest available memory chip, 512 MB to the iBookis one and only memory expansion slot. Those chips have not been showing up in too many places even though the iBook first rolled off the production line months ago. The reason this matters so much is due to the iBookis design and Mac OS Xis insatiable hunger for RAM. iBook users must upgrade correctly the first time, or risk throwing out that one memory chip for a newer, higher capacity chip later. Many therefore choose to move on up to that deluxe apartment in the sky and buy the biggest chip the first time out, and be done with it.
It seems the problem is scarcity of new components from the RAM manufacturers. The chips can be found, but this price list from Coast to Coast Memory earlier this week says it all.
32 MB Apple iBook - $ 9.00
64 MB Apple iBook - $ 12.00
128 MB Apple iBook - $ 16.99
256 MB Apple iBook - $ 44.25
512 MB Apple iBook (new iBook) - $825.00
A quick check this morning showed the price of the 512 MB module as "Call."
Another vendor, Memory X, is selling the 512 MB chip for a staggering $1095. Yet, these days have been known for historically low RAM prices. In the U.S., it can almost be described in terms of "pennies per megabyte," for every other kind of RAM. This kind of RAM is fully compatible in either PowerBook G4 slot with room to spare. Itis described as 144 pin low profile meaning itis less than 1.5". Itis a PC 100, 2-2-2 latency SO-DIMM.
By taking a few facts out of Appleis iBook Developer Note, some details begin to emerge. An iBook SO-DIMM can be no more than 3.8 millimeters thick it states, and no more than 1.25" tall. Thicker chips can not only cause reliability problems, they simply might not even fit properly. Appleis spec continues:
The maximum current specified for active operation generally rules out the use of 4-bit-wide SDRAM devices in a RAM expansion module. Such a module would have 16 such devices per bank, and the 1.2 A maximum current would allow only about 75 mA per device. To stay within the current limits, RAM expansion modules should use only 8-bit or 16-bit SDRAM devices.
What this means is that if cheaper, less capable chips are used, you need more of them. More means thicker (since theyire stacked) and hungrier (for electrical power). Hereis one more quote from the Developer Note:
The restriction on sleep current is required not only to maximize the battery life but to meet the limitations of the backup battery during sleep swapping of the main battery. Developers of RAM expansion modules that exceed the limit on sleep current must include a warning to the user that battery sleep swapping may not work with those modules installed.
This is just another reason manufacturers canit use the usual chips. And itis a suggestion to ask a vendor about sleep swapping, or look for the warning (if any) in the product literature.
So whatis the answer? Bruce Reilly from Techworks gave a good explanation on iBook RAM chip availability when we asked him for some help with this:
The "thick" boards are being made with stacked RAM. The iBook limits the height of the RAM module to where manufacturers can only physically fit 8 pieces of RAM chips side by side (four on the front and four on the back) on a module. Apple also specifies no more than eight RAM chips due to the current draw from more than eight chips. More than eight will draw more current from the battery and the motherboard than Apple allows. The "thick" boards have 16 chips, which draw more current (and produce more heat) than Apple provides for on the motherboard. This can cause not waking up from sleep, erratic behavior such as crashing, and poor performance from you battery.
Some manufacturers are doing this because the RAM chips required to properly make a short 512MB board for the iBook and Titanium PowerBook are not in production from the major RAM manufacturers-- we canit even get samples of these chips yet. Therefore TechWorks doesnit offer the short and "thin" 512MB modules for the iBook and Titanium yet. I havenit found any other RAM vendors that I can guarantee have the modules you are looking for (yet). I also donit expect the RAM chips to be available for these modules for at least a few months.
Although the PowerBook G4 can take iBook RAM, the reverse seems not to be true. G4is can accept "low profile" RAM thatis 1.5" or less. The iBookis tolerances are tighter at 1.25", so shopping for G4 512 MB RAM wouldnit be wise even though the prices are hovering well under $500.
Use the same guidance you would with any memory purchase. Ask questions before you buy and donit hesitate to go elsewhere if youire not getting the right answer. Make sure your memory comes with a lifetime warranty, and try to gage whether or not the company will even last as long as the RAM does. Lifetime warranties mean nothing if a company packs up itis proverbial tent over the course of a weekend. And in this case, make sure you can exchange it if for any reason itis no good.
In the meantime, this author has decided that spending $40 on 256 MB now is worth the performance bump one gets in OS X until larger chips arrive. We wonit blame you if you do the same.