Add memory to Imac G4 15 inch flat panel, help or advise needed

The computer you have requires two different RAM chips in
order to upgrade the RAM to the fullest extent as supported.

1 - PC-2700 200-pin SO-DIMM (user accessible),
1 - PC-2700 184-pin SDRAM (factory installed)

Maximum RAM: 2.0 GB (Actual) or 1.0 GB (Apple)

The upper factory slot where the original 256MB chip is stowed
is a harder upgrade; since the computer requires a bit of tedious
and fastidious effort to get into there and do it with great attention
to detail. The computer's processor has a thermal device to remove
heat from it and disperse it, and this has several parts; it must be
partially removed to access the section where this internal RAM
chip resides. And thermal paste in selected areas must be applied
properly and to certain specification for the computer to work right.

{The lower or user-replaceable upgrade slot is relatively easy and
it holds only one chip, the equivalent of a laptop profile 200-pin
so-dimm chip as noted above. These are available in 1024MB
specification, as are the more standard RAM in 184-pin for the
factory upgrade slot; which is harder to get into. The site you
noted where instructions were seen may not have included the
info on how to get into the harder to access RAM slot inside.}

While this type of computer is apart for a RAM upgrade, it is prime to
have the 3.6 volt 1/2AA lithium battery on the logic board replaced.
Any other internal considerations could be done while it is apart, but
only to the degree allowed by the design. Cleaning dust out of the
layers inside the half-dome base is also a good idea at the time.
since air circulation inhibited by dust can shorten the unit's life.

The optical drive, hard disk drive, RAM chips, clock battery, and a
few other parts can be either replaced (as needed, for repair or
upgrade) but little else. A fast spin-rate (RPM) hard disk drive
of about 7200 RPM and a large buffer of 16MB or so, and a
suitable amount of RAM in both slots, and perhaps as needed,
a superdrive replacement or upgrade (MCE had some listed)
can keep one of these going awhile; so long as no serious
hardware issues result over time. (Refurbished logic boards
and some other parts are among the more costly replacements
as this may be the breaking point in some owner budget if the
computer gets to the point where the LB or graphics go out.)

For some of the specifications for most things Mac, you could
download and use a free database from http://mactracker.ca
as your computer among others are listed. A handy little app.

Since the best step in Tiger 10.4.x is 10.4.11 and the last bits
for that including a Combo larger size file is a free download
to take the retail Tiger system to that last step, from Apple
Support online, the Combo 10.4.11 file and security updates,
plus Quicktime, Java, and Safari, are among some of the
later updates which the last version step of Tiger should be
installed first in order to use. 10.4.7 if on a retail - and not
a machine-specific (made for one model) disc - is OK. I had
a 10.4.0 disc set and since that was retail, it would work in
any supported Macintosh. A later Tiger retail bootable installer
is even better; so long as it is NOT a disc for only one model
& is not an upgrade disc; since they aren't a full install system set.

Be sure when doing a software install, upgrade or system update
or adding security updates, applications, etc, that you perform
the basics as recommended even though nothing appears to be
changing as a result; by this I mean, repair disk permissions by
using Disk Utility's click on for 'repair disk permissions' and also
when you restart the computer between installations of parts in
a sequence, occasionally start in SafeBoot and then repair the
disk permissions in Disk Utility; then restart normally.

There is more to know, but that would require some feedback
to see what and where you are going with this; and many bits
of information are available on the main Support site. Some of
the people here have owned many of the computers in question
and have some ideas. And some of us still have them!

Good luck & happy computing! 🙂

edited to add more words.

This is an informative post, and timely for me because I've been considering upgrading my G4 iMac to extend its useful service life. I'm especially thankful for the reminders about the batteries. Without them, I'd probably have gotten it apart and only then recognized the need.

The OP didn't say which instructions s/he got from Apple's website, but if it's [iMac G4 Flat Panel 15-inch (Original) User's Guide (Manual)|http://manuals.info.apple.com/en US/iMacG415inchFlatPanelMultilingualUserGuide.PDF], the only hardware upgrades it discusses concern the user-accessible memory slot and installing an AirPort card.

The computer's processor has a thermal device to remove
heat from it and disperse it, and this has several parts; it must be
partially removed to access the section where this internal RAM
chip resides. And thermal paste in selected areas must be applied
properly and to certain specification for the computer to work right.

What should one do to ensure those specifications are met?

Am I correct in believing that, due to the way interleaving works, it's best to install modules having the same amount of memory in each slot? (As opposed, say, to 1 GB in one slot and 500 MB in the other.)

Yet another after-thought:

I'd like to substitute a larger HD that is an exact copy of my current HD (OS, apps, data, hidden files, etc.). Is it possible to do this without having a 3rd, external HD to serve as a buffer? If not, I suppose a Firewire 800 drive would be best, but how does one transfer a carbon copy of one HD to another? I suspect that a simple select-all followed by drag-and-drop won't work.

I haven't found guidance on this topic in Apple's Support area.

The iMac G4 1.25 USB 2.0 computers support FireWire 400 so unless an
adapter is used (tested to see if it works) to run the FW 800 as 400, the
FireWire 800 is not recommended since it probably won't work directly.

Full computer clones using SuperDuper or Carbon Copy Cloner can do
the job; just be sure to test the results to be sure they are suitable, since
there are options in each clone utility which can give different results.

The multilingual pdf you cite is not the full service manual that is harder
to get and has been longed for by some home tech or hobbyists for a
time since they were no longer available from some web sites whose
use of them (as free download, etc) was not sanctioned by Apple and
these sites had to stop giving away those intellectual properties. The
original iMac G4 Service Manual in PDF for the 1.25GHz 17" is 16MB.

{I have a copy from the troublesome effort I went through with my iMac
under warranty, when CompUSA was unable to figure out the issues;
so I got the file and did extensive troubleshooting, and worked with
AppleCare directly (since CompUSA was inComp at it) to fix my iMac
and finally had AppleCare send parts and a directive to CompUSA
to just replace the parts as they were told, and not do further testing.}

That said, here is a takeapart page with some idea on how the iMac G4
is supposed to come apart. Whether or not any prying is required, is
unknown to me; I had not heard of the processor & heat exchanger as
being hard to remove. The thermal paste goes between the cooling pipe
assembly and in a second location (I forget the exact places now.)

"iMac G4 Take-apart for Drive and RAM upgrades" - xlr8yourmac.com
http://www.xlr8yourmac.com/systems/imacg4/imacg4takeapart.html

Since I've spaced out the earlier questions you raised, I am going to
post this now; I've been away from this site and sometimes don't get
into looking back more than 200 posts from the current dozen. Also,
I don't have automatic email notification enabled on posts here.

Hopefully the link helps. You can also save the page using Print and
selecting to save it as a PDF for offline use. I think it's about 14 pages.

Good luck & happy computing! 🙂

PS: Now I have three iMac G4 17" 1.25GHz USB 2.0 machines; two
work well enough, the third probably needs some major logic repair.
So, I have looked at the above link & may have to 'read up' again.

You may have to start a new thread and then ask the moderator
to move your posts here and my replies to that one; if you like.

I tried to edit, to add, but my post (the one above) was way big
and I ran out of time. You will have to re-clone back and forth;
since a drag and drop does not work on any system files; nor
does it do well to try and copy some installed applications if
there was a process via installer mechanism to place the parts
of the application in specific places. But sometimes they do
clone anyway and may work. Some do while others won't work.

You can use a higher speed ram than PC2700/333 in the factory
slot of the iMac G4 USB2.0 computer, but only one step higher.
Those are seen only as a PC2700/333 chip; but if that's all you
had, it will work. I have one in the inner slot of my iMac G4 in
use almost daily, it was an Apple approved Centurion or some?
thing. A desperate act, when a different chip failed and the repair
place I went to under warranty (who messed up the logic boards)
was no longer available; so I had to buy a different chip even when
the one I had previously bought had failed and had a warranty.

You can use the same chip in the 200-pin easier accessed slot,
as the iBook G4 1.33 12" last model (PC2700/333) uses, that is
here at the place I bought one a few years ago, from. The price
has come down, but it is an original 1024MB Apple Authorized
Samsung upgrade module similar to those shipped as new:
http://www.oempcworld.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=1.0G-S O2700LH-Samsung

Mine works fine and did not void the iBook warranty; and I trust
the Samsung (price is less now than I paid for same item) and
you do not interleave iMac G4 RAM. They are both different in
size, should be the same speed (no less than PC2700) and only
the inner slot of the USB 2.0 iMac using 2700/333 can use a
PC3xxx series faster chip. I do not remember the exact spec on
it; but the computer still sees them as PC2700/333 and this is
-only in the 184-pin factory slot. The other has to be PC2700.
And is the 200-pin low profile module. A PC2100 can't be used.

The iMac G4 USB 2.0 machines, the 17" and 20" especially,
and probably (check specs) the last 15" machine can use a
200-pin PC2700 DDR333 RAM module exactly the same as
the part used to upgrade RAM in the iBook G4 1.33 12" mid-
2005 last model and the 14" iBook 1.42 of the same series;
this in the user accessible slot in the iMac G4 bottom.

{No prying should be necessary to remove the heat pipes
or get the thermal exchangers apart to take the inner level
of the iMac G4 off the other part. There are screws to hold
the second section together, they require specific a torque.
That's the home of the factory installed RAM, the HDD,
and the optical drive. While inside install a new battery.}

Hopefully this helps and I didn't run out of time on this post... too!
If nobody can get you a service manual in pdf, see if a computer
tech can let you read theirs; it is not in hard copy, but is 16.8MB.

Good luck & happy computing! 🙂

Thanks for a pair of very informative posts. The webpage you cited looks quite helpful.

You're right about my iMac having only Firewire 400 -- I'd forgotten, so thank you.

I presume higher-speed memory may have the advantage of being easier to find, but won't speed anything up, being limited by the 167-MHz system bus speed. (Although: Does memory sit on the system bus? I'm thinking it's on a different bus for some reason.)

I've another question about the speaker connector, but I'll post that separately since it's a new topic (and I can award some points for your trouble that way!). 🙂

To answer my own question (for the sake of others who may refer to this thread): Memory does sit on the system bus. DDR (double data-rate) memory -- which is the type used in my G4 iMac and many other older computers -- uses a technique called "double pumping" to effectively double the bus (clock) frequency. Thus, a 167-MHz bus like mine calls for "DDR-333" memory.

One can use memory rated for higher speeds than one's bus permits, if necessary, but no gain in performance will result.

For further info, see [this Wikipedia entry|http://en.wikipedia.org/wiki/DDR_SDRAM].

Thanks for the very informative discussion. So what exactly is the max for user access slot. I just purchased OS X 10.5.4 Leopard w/i life update too. I tried to upgrade OS but disk just ejects after a few moments???

I shall keep reading and searching for max memory at most affordable bang for my buck.

I like many others like my lamp and will keep til it or me dies. The laptop will happen in good time.

thanks all,

biff

So what exactly is the max for user access slot.

According to [Mactracker|http://mactracker.dreamhosters.com>, your iMac G4 1.25 GHz (which appears to be the same as mine, BTW) can have a total of 2 GB (1 GB per slot).

The user-accessible slot takes a PC-2700 200-pin SODIMM (i.e. a low-profile, laptop-type module). The factory slot takes PC-2700 184-pin SDRAM. (PC-2700 means the module consists of DDR-333 chips.) The [iMac (All Models): Memory Specifications and Upgrades|http://support.apple.com/kb/HT3011?viewlocale=en_US] knowledge-base article mentions also that it should be 2.5 V.

I shall keep reading and searching for max memory at most affordable bang for my buck.

Be sure you can return/exchange it, if necessary. Cheap memory may be a product of lax QC.

I just purchased OS X 10.5.4 Leopard w/i life update too. I tried to upgrade OS but disk just ejects after a few moments???

If your drive reads other DVDs ok, it sounds like the disk is either unreadable or incompatible with your iMac. Is the label black or gray? Black ones are retail, full-install disks and should work with any Mac that, like yours, meets the hardware requirements. Gray ones come with a given machine and, according to reports I've seen, may not work with others that are configured differently.

I should also have asked: How does one safely pry apart the pasted part(s)? (The section I quoted implies this step will be necessary.)