Apple Macintosh iMac G5 ALS description

All in one desktop iMac G5 Macintosh which is great if space is limited.

The stylish, compact Macintosh desktop computer based on BSD Unix, as an alternative to more usual MS Windows.

I started making notes on this because the design sounded just about perfect for my regular computer use. Although the first version (August 2004 - EMC1989 or EMC2008) had hardware problems, I bought the second or ambient light sensor (ALS) model (EMC2055 and 2056) released in May 2005. My 20 inch model has a marketing model number M9845xx/A. See Apple article 301724 for details of how to identify different iMac G5 models.


2.0 GHz G5 Power PC with velocity engine, 667 MHz frontside bus. (original versions - 1.8 GHz G5 PowerPC 970 (3.0). 600 MHz FSB. 1.6 Ghz and 533 MHz FSB in other versions) 512 KB L2 cache on chip.

Processor speed can be halved to lower power consumption. In a hot climate, fans may run noisy if using top speed, or if doing processor intensive work. Cold climate may not be a problem. Doze mode turns off drives and display, but power and fans are on. Full sleep mode shuts down the power supply, except for a trickle supply to preserve the RAM state. Processor is powered off with state preserved. All non-essential clocks suspend. Meets Energy Star sleep requirements but can start without reboot. Awaken via suitable network package, keyboard or mouse activity, USB added or removed, or SMU scheduled wakeup. Off still allows Firewire to function as repeaters.

Display and Video
20 inch 1680x1050 pixel TFT active matrix or 17 inch 1440x900 pixel built in LCD. AGP 3.0 8x graphics. ATI Radion 9600 video with 128MB. VGA output; S video and composite video (640 x 480 at 60Hz, 800 x 600 at 75Hz, 1024 x 768 at 75Hz)..

Original version had Nvidia GeForce FX 5200 Ultra 64 MB video. Educational model had Nvidia GeForce4 MX with 32MB ram.

230 cd/m2, 350:1 contrast ratio reported.

Display supports mirroring, but not screen spanning. This appears to be a software block used by Apple to differentiate their consumer models from the more expensive professional models.

Although devised for the iBook a Macintosh screen spanning patch that also works with the iMac can be freely obtained. This changes a value in the OpenFirmware boot values. Certain video card drivers read this value to determine whether monitor mirroring or monitor spanning is available. Do not use this potentially dangerous patch unless you are willing to cope with resetting your nvram.

There are reports that the display on 20 inch model is more grainy than the original 20 inch Apple Cinema Display (which is claimed to be better than more recent 20 and 23 inch displays). Others say the 20 inch display is superior to the 17 inch display. There is no easy contrast adjustment, however using the System Preference Universal Access preference pane can adjust contrast. Monitor preferences may be set incorrectly to CRT by default (it was on my Powerbook). It is also possible that display is set for thousands of colors, instead of the correct millions. There are reports of improvement after color calibration.

M8639G/A display adapter for the G5 iMac is a special miniVGA, only of use on iMac G5. The dual monitor extended desktop patch called Screen Spanning Doctor for the iBook is reported to also work on the iMac. Use of screen spanning may raise internal temperatures too much for iBooks (Powerbooks have a large metal case as a heat sink, and they get hotter when spanning). Or it may just be turned off for product differentiation reasons.

A broken display would seriously reduce the use of the iMac, however in my experience displays are more reliable than the rest of the computer.

Weight, Size, Power
20 inch model is 11.43kg, 25.2 pound, size is 49.3cm x 47.2cm x 18.9cm (hwd 19.4 x 18.6 x 7.4 inches). 180 watt power supply built in. ALS versions use universal 110-240 volt power supplies. Original USA models were 110 volt only. Energy saving and sleep modes can be enabled.

Can be equipped with an optional Vesa display adaptor from Apple and could then be mounted on a heavy duty Vesa compliant monitor arm.

Memory and Disks
512 MB DDR400 (PC3200) SDRAM in a 184 pin slot. One free slot (I optioned to two @ 512 MB). Maximum memory is 2 GB.

Originally 256 MB DDR400 (PC3200) SDRAM in a 184 pin slot. One free slot. 64 bit access if only one DIMM is installed. If two identical DIMM are installed then 128 bit data access.

Serial ATA 7200 rpm drive of 160 or 250 GB, optionally 400 GB.

Original model was serial ATA 7200 rpm drive of 80 GB or 160 GB. (Educational version UATA/100 5400 rpm 40 GB hard drive)

Matshita DVD-R UJ-825 optical Super drive, write 4xDVD-R and 16xCD-R, reads at 8x and 24x. Some models have Combo drive. Educational version lacks optical drive.

USB keyboard with 2 USB1 ports (one for optical tracking mouse). Optional wireless keyboard and mouse require a model with Bluetooth. Note that some system diagnostics will not work with a Bluetooth keyboard, due to limited Bluetooth support from Open Firmware boot.
Audio line in, 12 watt digital amplifier, sound out as combined headphone and S/PDIF outlet, built in microphone, built in downward pointing stereo speakers.
Bluetooth 2.0+EDR, 802.11g Airport Wifi (both originally options), 10/100/1000 Base-T Ethernet (10/100 in original model), 56K V92 modem (modem not in educational version).
2xFirewire 400, 3xUSB2.0, video out, RJ45 Gigabit Ethernet, RJ11 modem (56K V.92), two USB1.1 on keyboard. External display connector supports VGA, composite and S-video.
Similar iMacs
This describes the M9845xx/A model.

Is it better than the last G4 iMac? Faster and more recent CPU, faster bus, larger low end display, lower price, less desk space. Yes, it is better value for money. The last G4 iMac display mounting was however much more flexible on its arm.

Has a Kensington lock slot for security.

No FM or TV tuner. No remote for iTunes or for iDVD.

Display support arm has a hole to assist with cable management, but does not turn and has no height adjustment.

Differentiated from the professional G5 PowerMac models by mirroring not spanning of display, Firewire 400 not 800, slower bus, only two memory slots, only one CPU, only one hard drive bay, slow video card, no expansion slots.

If you are considering video production, then you probably need to spend extra on a faster PowerMac G5 system.

Firewire 400 is still faster than USB 2 for disk drives. Firewire 800 devices are backwards compatible with Firewire 400 ports (cable required). This doesn't appear a major problem, especially as it is unlikely that a single disk could saturate a FW400 link.

User replaceable parts in original iMac G5

Apple Mac
Psion Epoc




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