iMac G5

In 2002 Apple introduced iMac G4 - the first iMac with LCD panel and with a novelty design. However, this design became source of many problems: LCD mounted in one point tended to fail, conductor cable could not survive twisting and servicing CPU was difficult. 2 years later, after developing a whole line of better and better "desk lamp" G4 iMacs, Apple released iMac G5 as a totally re-designed computer.
iMac G5 was another wonder of miniaturization - a whole computer fit into about 5cm-thick display unit on alluminium stand. The first model was released with 1.6GHz PowerPC 970 (G5) CPU and 17-inch display, but later models were 20-inch and had even more powerful CPUs. Many new technologies have been used in this iMac: DDR memory (earlier present only in Power Macs), advanced, system-dependent cooling and SATA hard disk was used too. A typical 3.5-inch hard drive could be fit inside.
PowerPC G5 are really hot processors, so hot that high-end Power Macs had liquid cooling systems. They tend to heat up under load, so to put anything more than 1.6GHz CPU Apple engineers had to design a cooling solution. They did it by installation of 3 turbine-like fans inside - two suck the air from inside casing and push it into a slot present on the rear. Cold air flows into computer from the bottom freely, except CPU block which has a third fan blowing right to heatsink's fins. Unfortunately such compaction of components made CPU cooling part almost unserviceable without removing a whole mainboard and the computer still operates on the edge of overheating. But from the user's perspective, if not under load, iMac G5 is usually silent. Under heavy load is starts to make noise.
Development of iMac G5 line included adding an iSight web camera and light sensor to make picture well in all conditions. The maximum CPU used was a single 2.1GHz one, as with this cooling solution it was just impossible to fit anything better to it. In 2006 they were replaced by Intel-based Macs.

Model No: A1058

Year: 2004
Discontinued: 2005
CPU: PowerPC G5 1.6GHz
RAM: 1.5GB
1GB+512MB in two DDR sticks
Max. RAM: 2GB
RAM Type: DDR 400MHz (PC3200)
Hard disk: 80GB SATA
Floppy drives: None
Other drives: CD-RW/DVD drive, slot-loading.
Graphics: Built-in GeForce4 MX
maximum: 1024x768?
Sound: Stereo, built-in speakers
Display: Built-in 17" LCD
Dedicated OS: Mac OS X 10.3
Maximum OS: Mac OS X 10.5.8
Expansions:  - Memory by DDR DIMM
 - USB
 - FireWire
 - AirPort card
 - Bluetooth board

Peripherals in collection:
 - None

Connectors:  - USB (3 ports)
 - FireWire (2 ports)
 - Ethernet
 - Phone
 - Power
 - Speakers/Mic
 - Display?

My unit was bought from a company who had it probably from import (Germany? After-leasing machines?). During its life its capacitors failed and someone replaced them. Later, hard disk has been replaced. Unfortunately Polish Post damaged the package (as they explained: because warning stickers were not in proper size). A few of plastic parts of rear cover have been broken and had to be glued back. Cyanoacrylic glue known as "Super glue" is enough to make the casing in one piece, but few layers have to be applied.

Hardware Disassembly


First about overclocking. Theoretically it may be possible to overclock G5, but I haven't got any sources about it. More, G5 are very hot processors and with so small space for cooling it won't give good results.
There are two links - first, a webpage of a man who tried to build a G5, when he cites asnother forum user (look for BadAndy) that modifying of frequencies is impossible without messing with firmware.
The second site is a theoretical AND ONLY THEORETICAL (please don't do it to your Mac!) site about overclocking a Power Mac G5. This is probably only half-valid, because we still have microcode problems to solve.
So it won't be easy to overclock an iMac G5 to get e.g. 1.66GHz from 1.6GHz :).
Next, capacitors.
Many G5 iMacs suffer from capacitor problems - they bulge and fail making computer unstable first, then preventing it to boot. Sometimes machine with damaged capacitors may beep and spin fans at the maximum speed, but this may also be a symptom of other problems. If capacitor inspection shows that theit cans are not flat - mainboard has to be removed and capacitors replaced.
So, the hard disk drive temperature.
Another technical issue is the hard disk temperature sensor. The small board with usually TMP75 chip, connected to the side of hard disk and to the connector under DDR slots. If you don't have one (this part is sometimes dropped in HDD upgrade), avoid using a high-speed hot 7200rpm disk. Generally 7200 WDs don't heat up too much, but Seagates do. It WILL overheat. See this for information, they all had problem with overheating Macs.
And the servicing.
The button closer to the fan is an internal power button. Because cooling without case in place is rather poor, it should be used in diagnostics only.
The button below it is a SMU reset button. Resetting SMU should be done if e.g. memory has been replaced and Mac doesn't want to turn on or is power management hanged and prevents Mac from starting up.
Diagnostic LEDs are located on mainboard and numbered on silkscreen:
LED 1. Power from AC is good.
LED 2. Voltages (12V?) from power supply is good.
LED 3. Logic board operation, generating video signal to LCD.
LED 4. Should NOT light. Lights up when computer overheats.


Proceed VERY carefully, it's easy to break plastic parts.
1. Put the Mac on a soft cloth, screen on the bottom, stand towards you.
2. In the bottom metal mesh, locate 3 screws and turn them left. They will not go out, they will not fall off, they will just turn a few turns and stop - that's all, do not try to remove them or twist them more. They only cause locking mechanism to shift and unlock, they don't directly keep case in place.
3. Open the rear plate with base stand slightly utwards you, and then pull it towards to remove from upper locks. This part is EXTREMELY BREAKABLE and hard to glue back. You have been warned.
4. RAM, AirPort card, modem and bluetooth can be directly accessed.
5. To get to drives: Remove the metal plate from 2 upper fans, then hard disk is kept with 3 screws on frame, optical drive with another 3 bolts.