A recent thread on hacking more memory onto a clamshell mobo caught my interest... and I wanted to segway here to talk about it.
So all kidding aside, what would seriously be needed to upgrade the base memory on a clamshell mobo? My specific clamshell of interest is the Bondi ("Rev A") machine [/selfishly eyes two sitting around the apartment], but other clamshells are worth talking about.
I know from other discussions that it is usually not as simple as "just soldering on more memory to open pads that fit", and removing the old chip to replace it with a new chip *may* work if a million things go right, but lets draw out a theoretical (yet practical) explanation of what one must do and how.
For some reason Apple only filled 4 of the 8 pads available. Assuming there isnt a flaw that prevents the pads from being used, you need to solder down the 4 new chips. AND, add whatever supporting SMT parts are needed, such as the capacitors. I could take a guess about which ones are needed, but its just a guess.
You could theoretically remove the 8 meg chips from a 300 MHz board and replace with higher density ones, but I dont know if you would have to modify the board in other fashions.
If anyone has done this, please let me know.
thanks,
Tom
The Developer Notes for the original iBook are sort of interesting reading. According to them the iBook apparently uses a version of the "Uni-N" memory controller, as found in the AGP G4/Pismo PowerBook, rather then the "Grackle" found in older machines with similar limitations. (For instance, the inability to use SO-DIMMs larger then 256MB) It makes one wonder what skanky things are going on in the motherboard implimentation preventing 512MB DIMMs from working in the slot, since they *should* work with that IC.
(Perhaps it's using some brain-dead revision of the chip.)
Knowing that it's UNI-N based my *guess* is that in theory you could acommodate up to 256MB onboard, if all 8 chip pad locations are "live". (If it were "Grackle" I would of said 128MB. UNI-N has different bank-size limitations. But the fact that the original iBooks seem to not recognize 512MB SO-DIMMs complicates matters, so.. who knows?) As for getting the machine to recognize it, that's another story.
If you were serious about starting this hack, I'd suggest comparing the motherboards of a 300Mhz "original" iBook with 32MB onboard to a later (non-Firewire) model with 64MB onboard. (Units sold after February 2000 have the larger RAM size but are otherwise identical until you get to the Firewire models.) See if the difference is that the "bigger" one has the other 4 pads filled with 8MB chips, or if it uses higher-density RAM in the same positions. In either case then you can look and see if there are any additional components are soldered in place, or if the position of any configuration jumper resistors differs. Whatever the difference turns out to be the next step would be to obtain 4 appropriate memory ICs off an old DIMM and try to upgrade your 32MB board to 64MB by making whatever changes are necessary to match the newer one. If *that* works, then I'd suggest obtaining the next-higher-density ICs and working up from there.
Honestly I think your best hope is if comparing the two boards reveals that the later models used higher-density chips and a jumper is moved. That would imply the motherboard is flexible enough to accomodate more RAM without excessive fiddling. If it's done through doubling the number of ICs it'll probably be a lot harder to figure out how to inform the memory controller that more RAM is available.
--Peace
It's not a complication - all iBooks (including clamshells) can recognize and use 512MB SODIMMs. The devnote is wrong. Well, without reading it, it may just say that 256MB SODIMMs are the largest 'supported', not quite the same thing as 512MB not working. Typical conservative Apple techwriting.
dan k
Is that really true? I could of sworn that 512MB SO-DIMMs didn't work in the pre-Firewire models.
Eh. So scratch that as a complication. ;^)
--Peace
So I'm wrong . . .
Uhm, yeah, right, sure, OK.I've added 512MB sticks to several clamshells - in my experience, as long as it fit it worked.
dan k
Hmm, nevermind.
eh? Anyone have any solid knowledge on those empty pads?
dan k
i might have a go at adding some more memory once i get my clamshell
I'm pretty positive that the Rage Mobility video chip in those machines has the VRAM integrated into it. (And the page in the Developer Notes backs that up, as does the Rage Mobilty page on ATI's site.) I think the only way it can use additional RAM is as texture space over the AGP bus. (Which Apple's OS X drivers never supported in any meaningful way on GPUs older then the Radeon series because of the power-of-2 texture size limitations.)
--Peace
...the last time I went looking for memory, the most I could find was 256MB sticks. I would like to get some of that. Where did you get it from and can you point (read as "good hard shove") me in the right direction?
I need 2 or 3 sticks of that stuff!
Both OWC and DMS are good vendors whom I've used numerous times with only positive results.
dan k