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mdd2

In my previous article I talked about the Macintosh G4 and specifically the “Digital Audio” model. This time I’m going to talk about another G4 Mac sometimes referred to as a DRR G4 but more commonly known as the MDD or Mirror Drive Door model. Looking at the images above and below it becomes fairly obvious how these machines got their nicknames.

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The case overall is basically the same as the Digital Audio versions case and in fact all the G4 tower PC’s are similar with exception of the face and back. The case color scheme is more silver this time around as well as the cases area of the two drive bays has a mirror like plating, hence the name. This is actually quite reflective and I guess is useful to see if your being snuck up on while browsing on OS X or as a impromptu weapon against Medusa attacks. Also on this mirror finish section we have the power button at the top which glows a nice white when powered on as well as a welcomed frontal audio jack for headphones. The speaker is now placed at the very top with four decorative vent looking recesses at the bottom. Missing are the reset button and programmers button found on the Digital Audio and earlier G4 tower cases.

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The rear of the MDD is the opposite layout of the earlier Digital Audio case. This time the expansion bays are at the top while the various ports and jacks are near the bottom.

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The available ports are exactly the same but in a different orientation. Two USB 1.1 and two Firewire 400 jacks followed by Ethernet and modem jacks and finally an audio output jack and a jack for those Apple high definition speakers. The only addition is an audio input jack next to the audio out.

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Opening the case is the same as before and super easy with a side handle that pulls up and away.

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Inside it’s basically a reverse layout of what we saw in the Digital Audio machine.

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On the section of the case that does not fold out we have two full 5 1/4 drive bays for optical drives as well as a fan and three spots for hard drive mounting. Two 3 1/2 inch HDD bays under the 5 1/4 inch bays and one vertical oriented 3 1/2 inch HDD bay to the left under the power supply. I have two hard drives currently installed. One 80GB drive that holds Mac OS X 10.5.8 and a second 180GB drive for data.

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Like other G4 motherboards the MDD motherboard has quite a few chips soldered on underneath making the board look slightly bare from the top.

1) CPU – The MDD model G4s came with many CPU options up to dual 1.42ghz G4 PowerPC 7455 chips. Mine was the lowest powered model and came with dual 867mhz chips with a 133mhz front side bus. Note that many models in the MDD line came with dual CPUs on a sort of CPU module. As I said previously in articles its hard to compare the power PC to the far more common Intel X86 CPU’s in speed but this would roughly be equivalent to a Pentium 4 or maybe a 1.4ghz Tualatin PIII but this is only a rough guess.

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2) RAM – four slots supporting up to 2GB of DDR RAM which is also why this model is also sometimes referred as the DDR G4. Unfortunately the Power PC 7455 can only use at most 50% of the DRR RAM bandwidth meaning there is no improvement over the previous models and their PC133 SDRAM as far as memory speed is concerned.

3) Four 64 bit PCI slots (which work fine with regular PCI cards) as well as one x4 AGP slot for video. Keep in mind that if your using a x8 AGP card whether a MAC card or a PC card that has been flashed with a mac BIOS you need to disable pins 3 & 11 to get video. This applies to all G4 Mac’s with the exception of the AGP 2x Sawtooth models. This issue is due to apple using the at the time unassigned pins 3 & 11 for the “ADC” apple monitors connection. When AGP x8 came out those pins were suddenly used for something else so basically they wouldn’t run on a G4 Macintosh. The way around this is to disable the pins completely either by taping over them or cutting the traces making the card AGP x4.

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The card I’m using in this machine is a Geforce4 MX. Not a particularly interesting card but it more or less does the job. The MX was a budget card and less advanced then even the preceding Geforce3. For me it’s enough since I really only use this machine for one game and messing with OS X but the MDD G4 can support up to a Geforce 7800 GS with the earlier mentioned Pin modification.

4) Wireless airport adaptor for wireless internet

5) IDE connectors – There are actually three IDE connectors but one is obscured behind the huge CPU heatsink. The one located behind the heatsink is an ATA-100 connection intended for your primary hard drive.

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The two connectors located at “5” are an ATA-66 connector for two secondary hard drives and a ATA-33 that is intended for the optical drives.

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Regardless I have a separate Sonnet ATA-133 PCI controller card installed in my machine for the optical drive and main hard drive while my secondary hard drive is attached to the ATA-66 labeled connector.

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6) CMOS battery used for saving settings.

Upgrading the CPU

I decided to upgrade the CPU in my MDD Mac since the CPU it came with was barely what I needed to do what I wanted to do with this machine. Third party CPU upgrade kits seemed to be overpriced so in the end I decided to go with a cheap $25 upgrade to a single 1.25ghz CPU. Now the value of this upgrade is somewhat debatable since I was going from a dual CPU configuration to a single CPU and OS X can take advantage of dual CPUs but my main purpose of this rig was to play a few select games which didn’t really take advantage of dual CPU anyways so I figured the 383mhz bump was worth it.

When considering a CPU upgrade for any G4 Macintosh keep in mind the CPU modules are not compatible across models so make sure the CPU your looking at is specifically for your model, for instance for a MDD model or Sawtooth G4.

I also wanted to (and needed to with this CPU upgrade) bump the front side bus speed up from 133mhz to 167mhz which required a small modification to the motherboard.

First disconnect any cables from the motherboard and then remove the currently installed CPU which can be done by unscrewing the various screws holding the heatsink on and then gently disconnecting the CPU module from the motherboard. It will look like this with the module removed.

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next unscrew any screws fastening the motherboard to the case and remove. The modification we need to do to enable 167mhz FSB is the desoldering and removal of a resistor on the underside of the motherboard.

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The piece we need to desolder is labeled as R676 and is located near one of the corners of the large black heatsink.

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Desolder this component and that’s it. You can now install a faster CPU and have a slightly higher FSB.

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The final step is to reassemble and install the new CPU. Here is my 1.25ghz G4 CPU module before installation and reapplying the heatsink.

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And lastly booting the machine and checking the system information to confirm everything.

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I like the MDD G4 Macintosh. It’s super easy to work on and plays the few early 2000 OS X exclusive games I need it to play just fine. It does have its issues though. It’s a shame there was no real improvement with the DDR RAM being used over the older PC133 SDRAM. Also upgrading the CPU if you have an early model like mine can be a small chore requiring a modification not to mention the modification needed to use a more powerful AGP video card. Another problem is the fan. This machine can be pretty loud and I noticed it is significantly louder then my Digital Audio model G4. For me the fan isn’t to loud and doesn’t come anywhere near the noisiness of my dual Tualatin rig but I can see how it can annoy some people and the noise level did seem to be a common complaint when I was doing research on the model. I would still recommend a MDD model though if you just wanted to casually mess around with those few early 2000’s OS X games and you can pick up a rig cheaply.

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One Comment

  1. I love your blog! Apart from being great as a history lesson, I found some very handy and valuable information here, which is I think beacouse you pay attention to details and perspectives that other web sites tend to over look.
    Keep up the work, you just got (an other) fan!


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