1GB stick in 1.25 GHz G4 not working

For the factory slot upgrade, you can use a later spec PC3200 that is compatible

in the important ways, and it will be seen by the iMac G4 as the slower (PC2700)

speed; & is backward compatible. Works for my iMac G4s with 1.25GHz cpu.

1GB 184pin DDR DIMM 128Mx64 non ECC gold leads unbuffered 2.6 volts PC3200 DDR400 spec 400Mhz with SPD CAS 3 latency CL3

Link to example of this exact spec back-ward compatible RAM that is seen by

the iMac G4 (17 or 20 in) 1.25GHz computer, as correct PC2700 in use, here:

http://tinyurl.com/compatible-spec-184-pin-RAM

Of course the other RAM slot uses a PC2700 laptop chip exactly the same

spec as a Mid-2005 iBook G4 1.33 or 1.42GHz. Nothing less in quality; a

few brands are out there. You can get RAM from OWC macsales or Crucial

online and perhaps they go back this far. I've bought from example company.

If the upgrade chip in the factory slot reads at 256MB by itself, and you add

some off-brand 1024MB laptop RAM chip into the user slot, the total should

not be 1.5GB; the math does not add up. One or both may be defective.

So, if you do choose to upgrade the computer to a full 2GB, the upper slot

should have a 184-pin chip spec linked above, since otherwise you'd have

to find the correct older PC2700 from three different ones by guesswork.

Incorrect chips in either slot may cause issues, or partial failure to function.

Some makers do not have exact spec matches for Mac hardware needs.

When I got my 200-pin SODIMM PC2700, I bought more costly samsung.

And I got the chip knowing it would also fit my iBook G4 mid-2005 model.

1GB 200pin DDR SODIMM 128Mx64 non ECC gold leads unbuffered 2.5 volts PC2700 DDR333 spec 333Mhz with SPD CAS 2.5 latency CL2.5 max 1.25 inches tall Tiny BGA

Here's a similar example of less costly (non-samsung) spec user-slot RAM

http://tinyurl.com/PC2700-200pin-SODIMM

Bad RAM can lead to kernel panic and excessive handling of RAM may

cause it to short out, or a static charge through the logic board can do

damage to the population of important integrated circuit bits on there.

Not exactly certain why you have the problem stated above, but the RAM

you have should register correctly. You could have incorrect spec RAM

for a windows-box and not correct for a Mac PowerPC G4.

(Oh, you can just type a period ( . ) to bump a thread. The PowerPC iMac

section is not very active compared to newer hardware discussions.)

•Resetting the iMac (Flat Panel G4) Power Management Unit (PMU)

http://support.apple.com/kb/HT1712

•Reset PRAM (about NVRAM & PRAM)

http://support.apple.com/kb/HT1379

Since you've gotten into the non-GUI method, single user mode or terminal

that is where you've lost me. By swapping RAM and getting errors, part of

the problem may have been avoided by replacement with exact spec RAM,

and a PRAM reset. Perhaps even a PMU reset. At this time, I'm not certain

when you'd use the reset button on the logic board, near the AirPort card

and user-RAM slot. Been awhile. I believe it to be for PRAM reset as the

topic comes up in service manuals, to try that after a power outage; or if

the internal battery may need replacement.

•iMac G4 Take-apart for Drive, RAM upgrades: (+ PRAM battery)

http://www.xlr8yourmac.com/systems/imac_g4/imacg4_takeapart.html

•Mr Totes iMac G4 take-apart:

http://www.mrtotes.co.uk/page1/page1.html

Hopefully some of this helps eventually 😐

KomputerBay chip may be incorrect (or of too-loose specs) to work

in that computer model. If it were a cheap PC, they'd likely be OK.

The chip installed by an apple reseller may or may not be correct.

Just because a geek-guy or some other expirt said so. I've been

there and had 'experts' do very bad things, under AppleCare, to

my computer. To include installation of bad RAM in the upper slot.

Since the iMac is an older model and sometimes had logicboard

issues that would totally disable it, if the resets, new 3.6v 1/2AA,

or other ideas include running a replacement 184-pin 2700/3200

RAM, to attempt to troubleshoot or establish a baseline, I'm not so

sure what else may be wrong with it now.

When the power supply fails, or a hard disk drive fails, these also

can happen at inopportune times and mimic other symptoms.

That's why it's good to have at least two of the same model iMac... 😐

You may have to inquire of AppleCare or Apple Sales (online store) and ask an Mac OS X operating system expert about Replacement OS X DVDs with white labels; in OS X 10.4 and also OS X 10.5. These are for PowerPC Macs and you'd need to supply a serial number for them to get you a match. And these sell for about $20 each. These replace a retail disc for those supported computers whose original configuration could use a retail DVD for a full installation; so the white label disc should work across several models, because either one is not a machine-series specific install/restore disc (not to replace grey disc) with wider compatibility.

That may be able to get you an equivalent of either or both full install DVD media for Tiger &/or Leopard. I have both sets of OS X DVD in retail media, and also for those who shipped with an OS X, their original grey label install restore disc. Plus, I found a nice 'drop-in full-upgrade' Leopard 10.5 DVD that does not require a prior Tiger for it to work totally in the same ways as a retail DVD does. Some argue these do not exist. (Rare.)

One of my iMac G4s has Tiger 10.4.11, another has Leopard 10.5.8; a third half-way boots, enough to tell me it would be a parts source for issues the other two have.

Not sure if this link may be of help. Note the size since I have not checked that lately; should be a guide to troubleshoot and may be up to 7MB download. If so the info may be of help since it does cover service issues. Looks to be about 200 pages...

http://tinyurl.com/info-pdf-USB2-0-iMacG4

Oh there are ports or tiny holes in the vicinity of the reset button under the bottom plate of the iMac G4 1.25GHz model where you can use tiny probes and test power supply (and PRAM battery) power.

Hopefully your iMac can be convinced its safe to come out of single-user or command line. One of mine needs something, again, maybe the PRAM battery. And/or hard disk drive...

PS: The 800MHz 17" iMac G4 I had, dual-boots OS 9.2.2 & OS X 10.4.11; superdrive, wi-fi card, and other options; gave it to a friend with a pile of software and accessories. I think they've let it sit; now it needs a new 3.6v 1/2AA lithium battery and someone (not me) with time to mess w/ it.

Don't have the time, though. 🙂

Yes, the limits of RAM to the system do make a good amount of difference; since the other factor is Virtual Memory where any blocks of unused or free-space on the hard disk drive are then used in a slower speed method of swap files; space on hard disk drive is used as read-write temporary memory. And it is Slow.

For the sake of reference I suggest you check out the pdf in the link, and save a it to something such as a USB flash drive. Some of the older manuals I have, yet don't use often, are saved in duplicate, separate locations.

Hopefully the RAM slots in the iMac G4 have no damages that could contribute to the chips not appearing correctly. Usually a problem is in some off-brand of RAM that may not be exactly accurate in the Mac. Some do work for a time, then under a load, they tend to fail. Kernel Panics and other odd effects occur. Not all of them result in a multiple language prompt screen to restart.

Did you find any Console logs from the system, or any revealing crash logs, or other time/date files to indicate what has been going on with the RAM or resources in the system when the issues re-occur? The System Profiler can also tell a few things about how the system is, and if the RAM appears correct... which is subject to change with flakey RAM quality. Activity Monitor also can tell you where the usage is going.

Anyway, thought I'd check back.

I have stuff to do outdoors, plus am attempting to care for an elder. 😐