Building an Apple Macintosh

Mac-envy on a budget? – Michael Hughes

NOTE: In response to the number of emails I have received since posting this article, I would like to make clear that while I did mention price as a motivating factor in my building the Macintosh, the most important reason why I did it was to build an Apple computer. I was fully aware about half-way through the project that I wasn’t saving any money; however I still consider the project a success because it did produce a working Macintosh.

I would also like to make clear that this computer wasn’t intended, nor ever will be used, in a manner that requires modern memory technology or higher CPU clock speeds. In fact, it will most likely be the only Apple computer I ever use at home.

Preface:

This project was the result of me wanting to try the Apple OS and computer system but not wanting to pay the (to me) outrageous prices for the system to just simply toy with it. I am a PC person – I have used PCs for years, I have a “home” network of 4 computers and have built a number of PCs. Being the tech junky that I am, I decided to combine my first Apple OS experience with the experience of also building an Apple computer.

Sadly, this project would cost more than I had budgeted because I was sent a junky part that the seller said was working. Moral of the story: Always be careful about buying used electronics. However, overall the project has turned out well and I have learned a great deal from it.

Also note: I am no Apple expert, so if there are any informational errors, please feel free to point them out. Finally, the article may seem slightly confused due to the fact that I tried to write it in the same order that I built the system.

The first part of the project was to decide which components were needed and how the system was to be built. First, the different Macintosh models: the most current models are based on the G5 CPU. The next oldest set of models was based on the G4 CPU, which was preceded by the G3. For this project, a system based on the G4 CPU was the most appropriate.

This is due to the lack of G5 parts, namely, freely available CPU’s and motherboards (logic boards in Apple speak). The G3 was not chosen for the reason that while plenty of parts were available, the system was getting long in the tooth and the point of the project was to build something at least semi-modern.

This Apple G4 system project is a based on a Power Mac G4 system. The G4 Power Mac had a number of iterations, some of which were minor changes and others totally changed the system. The project was originally to be based on the G4 AGP graphics logic board; however this plan was dashed due to defective parts. So the model this project was built on is the Gigabit Ethernet Power Macintosh G4, which uses PC-100 memory.

The Gigabit Ethernet model implements gigabit ethernet and also supports dual CPU daughter cards, like the other Macintosh G4s. This Apple computer project would be built using a 450-600 MHz processor; this decision was made because the system was being built to experience the Apple OS and not much else. In the end due to circumstance, namely what was included in a package of parts that was purchased, the CPU that was bought was a G4 500 Mhz.

Fortunately, a number of Apple and PC parts are interchangeable if the right choices are made. These interchangeable parts include CD-ROM drives, hard disk drives, memory and input devices (keyboard, mouse, etc.) By using interchangeable parts, money was saved in a number of areas in this project. However, the cautionary part of this is that like a PC, an Apple computer has a basic input output system (in Apple’s case it is a modified version of Open Firmware), and this BIOS has to load basic device drivers when the system is first started to operate the system’s hardware.

In this project’s case, it was discovered that at least one piece of hardware did not have the required device firmware to initialize at the BIOS’ command. This was an old NEC CD-ROM drive. Other than that CD-ROM drive, no problems were experienced in using two PC hard drives, a new PC CD-ROM drive, PC-100 memory, a PC keyboard & mouse, and finally a PC monitor. The final note to make about this section is that by using existing parts, only one new HDD and CD-ROM drive had to be bought. The memory was scrounged from another computer, and this project computer was going to be used in conjunction with an existing PC which had a dual monitor setup with a KVM switch already set up for a second computer.

(Note: This site has a great drive compatibility database for this sort of thing)

The other parts that needed to be considered were parts that were Apple only, namely a graphics card and power supply.

The graphics card, like the CPU, needed to only to be sufficient to run the latest Apple OS. This, combined with a package deal that was obtained from eBay, lead to the choice of an ATI Rage 128Pro graphics card. This card is sufficient to run Quartz in OS X, which was all that the project needed.

The power supply was a problem, as new ones were hard to find and expensive, and Apple used a different power supply for several of the Power Mac G4 models. Originally, when the plan was to build a AGP graphics system, a power supply came with the package of hardware ordered. However, when that plan fell through and a Gigabit Ethernet logic board was purchased, it was discovered that the power supplies were quite different.

Since at the time no Gigabit Ethernet power supply could be purchased for the desired price, it was decided that a Mirrored Drive Door G4 power supply would “adapted” to the purpose.

The other two things needed for the Apple computer was a case and an OS. The decision on which OS to buy was easy – the most modern version of OS X (10.3) would was used for the best experience possible. To cut costs, a modified PC case was used – fortunately it was free.
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Part II: General Construction Theory of Apple Power Macintosh G4 Computers

For the most part, Apple G4 desktops are very similar to desktop PC except for a few important considerations:

Cooling is handled in a different manner than in a PC: on lower clocked G4 CPU ,there are no heatsink fans. Also, there is an additional heatsink on the back of the logic board that requires cooling. Most importantly, the Apple case design essentially sets up a wind tunnel that blows air across the two heatsinks on the top and back of the board. To properly cool all of these components, it is necessary to copy the Apple wind tunnel idea when using the logic board in a PC case.

Another consideration is that because of the heatsinks on the back of the logic board, more clearance between the board and the case is needed for a G4 logic board than a PC motherboard. To solve this problem, a set of large standoffs are needed to give the extra space between the case and motherboard that is needed.

In addition to extra clearance being needed between the board and the case, the holes in the G4 logic board are unlikely to line up with the holes in any PC case; therefore new holes will have to be drilled and tapped in the case to secure the logic board.

Add-on cards, such as USB risers and graphics cards, are also a consideration. Basically, for an add-on card to work with Apple hardware, the miniature BIOS contained on the card must have the correct code to operate with the Apple BIOS. While the occasional PC card BIOS may be flashed such that it has the correct BIOS to operate with Apple hardware, there is a high possibility of rendering the card inoperable in the process.

The power supply for Apple G4’s is also different than that of a PC. What is important to note though is that a PC power supply does provide enough power for all of the system components of an AGP graphics logic board to work. Models after the AGP graphics model require two extra power lines, one of which can be ignored. The two extra lines are a 12+ & 24+, with grounds. The 12+ line and ground have to be connected for the board to operate properly.

The 24+ on the other hand can be ignored because all it does is provide 24+ to an extra connector next the AGP slot on the logic board. This extra 24 volt connector is used to provide power for the use of an Apple ADC monitor. Since this project used a monitor and graphics card that didn’t need the connector, it wasn’t a big deal.

The final consideration for supplying power to an Apple logic board is that following the AGP graphics model, all of the logic boards had those extra two power lines, therefore all of the power supplies for each of those late models are mostly interchangeable provided that they can provide sufficient current for the logic board.

The final important consideration to make note of is the method of attachment for the CPU. The Apple CPU is not just a single chip that plugs into the board. Instead, there is a socket on the logic board which a CPU daughter card is plugged into and the daughter card is then held down with three screws. The daughter card is necessary to allow Apple to give the G4 CPU the relatively large 2MB L3 cache it needs to operate efficiently.

This daughter card design makes it possible to run dual CPU systems using just about any of the G4 model logic boards. However, the problem is that both the daughter card and logic board have exposed pins which can be easily bent or broken. {mospagebreak}

• I. A PS/2 to USB converter that was compatible with Apple Computers
  • $29.99 from Amazon Market Place
• II. A combination of a G4 500 MHz processor, ATI Rage 128Pro graphics card, a Power Supply, and an AGP graphics logic board.
  • $332.00 from Ebay
• III. A 60mm Vantec Case Fan
  • $6.99 from Outpost

At this point enough parts were on hand to build a semi-functional system that could be used for testing. Since no OS had been bought yet, the test objective was to ascertain whether the parts on hand were in proper order by trying to access the open firmware BIOS of the logic board.

This testing was simply done by setting the computer up on top of several pieces of anti-static bagging, and then using the Rube Goldberg method of making a contact switch by tapping two pieces of wire together. Basically, the results of this test were inconclusive because of the lack of knowledge concerning the Power Mac boot sequence.

Later, after a number of hours of research, there was great doubt as to the hardware’s operability because of the lack of response to even simple boot commands which access the system BIOS. However, there was still hope that the hardware was usable.

I. Macintosh OS X 10.3 – $59.99

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With the OS X software on hand the projects testing phase with the first set of hardware continued, however the hardware refused to be responsive to any type of combination of key combinations of start-up sequences. Eventually, after many hours more of research and testing; the hardware was taken to a local Apple specialist to test the logic board, memory, graphics card, and CPU. After two days the results came in the logic board was dead. At this point the project was nearly canceled because of the difficultly in finding another logic board. However, because of the money already invested in the project, it was decided to continue and find another logic board.

I. Apple Gigabit Ethernet Logic Board – $297.00 from eBay

At the time when the Gigabit Ethernet logic board was purchased, insufficient research had been completed about Apple power supplies; as a result, it was only found out after the new logic had been purchased that the power supply for the AGP graphic board was incompatible. The incompatibility was due to the differences in the socket and that the AGP graphics power supply didn’t supply 24+ to the graphics connector on the mother board for Apple ADC monitors. The ADC capability on the Gigabit Ethernet logic board would never be used but the possibility had to be there.

After some searching, no Gigabit Ethernet power supplies could be found for sale. However, this was solved by adapting a power supply from another Macintosh model. Since all of the Power Mac G4 models after the Gigabit Ethernet model had the extra ADC power connector (and ground), it was a simply matter of obtaining a power supply would could be modified such that it supplied power to the correct pins on the mother board.

The power supply that was chosen for this task was a new power supply for a Macintosh Mirror Drive Door G4 – these power supplies are comparatively cheap and have all of the correct voltage outputs.

I. Mirror Drive Door Power Supply – $100.00 from eBay
II. Random Hardware for PC case conversion – $25.00 from Parkrose Hardware (Local Store)

Before testing and construction could proceed, the new power supply had to be adapted to the Gigabit Ethernet board. Fortunately, Apple provides power output and input diagrams for the various Apple G4 Power Macintosh models. Once the information on which pins needed in terms of power, it was a matter of rearranging the Mirror Drive Door Power supply to fit.

However, there remained one problem: because the connectors were different on the logic board and power supply, the pins had to be removed from the power supply connector and then put onto the logic board pins. This left the pins without any insulation and quite liable to become disconnected. The solution was to use generous amounts of hot glue – the hot glue both attached the power pins together and insulated them from short circuits.

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The entire system was reassembled for the third round of testing with the donated memory, hard disk drive, CD-ROM drive and the other parts which had been purchased. The system booted and reached the Apply screen, at which point it halted due to the lack of an operating system. This was the first big success of the project.

However, this would soon be halted as it was discovered that the CD-ROM drive which was currently being used for testing, an old NEC, wasn’t compatible with the Macintosh and couldn’t boot OS X from CD-ROM. Another drive was borrowed to ascertain that everything was in proper order; the new drive, a HP CD-RW, worked perfectly when tested for booting.

It had been noted from previous research that there was a chip on the back of the Gigabit Ethernet logic board that needed the help of a heatsink to stay cool. In addition, it had also been noted that a PC case does not maintain the same wind tunnel like design of an Apple case for cooling the processor heatsink and other components.

Luckily, the first logic board purchased for the project had the Apple heatsink to cool the chip on the back of the logic board. This heatsink was removed from the defective logic board and then cleaned off.

Aside that, when cleaning this heatsink a strong solvent was needed, as the thermal tape adhesive is very strong. Since the heatsink would not probably have to be removed again, it was attached to the chip with thermal adhesive; fortunately this was already on hand, but is about $8-$10 new.

The other matter, the wind tunnel design of Apple case, was replicated using a small fan which had already been purchased. This case fan was placed on the bottom unused shelf in the PC case’s drive cage. This sent a flow of air in approximately the correct direction to cool the logic board.

It was decided that the OS should be installed with the hardware out of the case in case of any problems. The borrowed HP CD-RW was used for this, as a new compatible drive had not been purchased yet. The installation of the OS went without a hitch onto the old 12 GB Maxtor hard drive which was borrowed from another computer for the Macintosh’s system files. There was not any time to play around with it yet since there were still many other things to complete.{mospagebreak}

There are several important things to note about the case:

It was a Dell computer case with a proprietary connector from the Power Switch, LEDs, and Reset Switch. The other thing to note is that standard brass standoffs would not work for this application because more clearance is needed between the logic board and case due to the heatsink on the back of the logic board.

The final part was that obviously none of the logic board’s and case’s standoff holes lined up.

The first part, the power switch that was done involved a painfully long series of tests. First, the switch and LED assembly was removed from the PC case. It was then decided, to reduce complications, that only the power switch and reset switch would be electrically connected. The testing was done by taking a continuity tester, then depressing the power button and using the tester to run through all of the wires to find the two with a 0 ohm resistance.

The same procedure was used to find the two wires for the reset switch. The first logic board purchased for the project came with a bundle of cables with the connector for the front panel header on the logic board. Thankfully, this set of wires still worked with the Gigabit Ethernet board, and since the power, reset, and ground wires had already been labeled on it, then it was a matter of soldering the two sets of wires together.

That was done and tested with the Macintosh hardware – the Dell switch worked perfectly.

The next two concerns with using the PC case were handled at the same time.

To allow the Macintosh logic board to operate in the PC case, what was needed were larger standoffs, a drill and tap. To support the logic board, 8 new standoffs and holes had to be created. The standoffs were made out of a threaded nylon spacer, a nut and a threaded rod which would be put into the spacer and then locked into place by the nut.

Next, the logic board was placed into the case in the position that it would rest in and all of the needed holes were marked using a sharpie. Once the holes were marked, they were drilled out using the special tapping drill and then they were tapped to proper size and threaded for the spacers. With the spacers and holes completed, the logic board could be put in the case.

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I. Lite-On CD-ROM drive – $16.99 from Directron.com
II. Seagate ATA Barracuda 80GB Hard Drive – $77.99

This Macintosh also had a second purpose. In addition to the Apple computer being build to experience the OS, it was also being built to act as a back-up computer. For the computer to act as a back-up machine, a much larger hard drive was needed. A Seagate 80 GB ATA Barracuda drive was chosen for the reasons of reasonable cost, noise, and reliability.

Also, another CD-ROM drive that was compatible also was needed; a Lite-On was decided on for the purpose because of its low cost. Both of these parts were then purchased and placed in the system for a complete Apple Power Macintosh G4.

This project’s objective was to build an Apple Power Macintosh G4 utilizing Apple latest operating system, OS X 10.3. To that end, a collection of parts was bought from eBay; this contained most of the parts needed to construct the system from scratch.

However, through testing it was found that the logic board that was contained within that set of parts was defective. To continue, another logic board was purchased, which facilitated the purchase of another power supply. A Mirror Drive Door power supply was then modified such that it would supply power to the correct pins on the Gigabit Ethernet logic board.

Next, a PC was taken apart and the parts reassembled to work with a Macintosh. New holes and new standoffs were created to fit the logic board properly. Also the various power switch cables were tested and then soldiered together to control the Macintosh.

Finally, a new CD-ROM drive and a second hard disk drive were bought to make the computer usable as a back-up system.

• PS2 to USB converter – $29.99
• Parts Package – $332.00
• Case Fan – $6.99
• OS X 10.3 – $59.99
• Gigabit Ethernet Logic Board – $297.00
• Mirror Drive Door Power Supply – $100.00
• Random PC Case Conversion Hardware – $25.00
• Lite-On CD-ROM drive – $16.99
• Seagate ATA Barracuda 80 GB Hard Drive – $77.99

Michael Hughes