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8500 ATX
Dan Calhoun's 8500 to PC ATX Case Conversion
Published: 1/28/2000

    Disclaimer/Warning: This page is for reference information only and is not guaranteed accurate. Performing modifications or other work inside your Mac will void your Apple warranty, may cause damage to your computer or result in personal injury. Although Dan indicates he made these modifications successfully, neither the site publishers nor the author warrants any of the information listed here. This article is published for entertainment purposes only. The modifications listed here are beyond the capability of most end users. The author and site publishers DO NOT recommend attempting any of the mods listed here. You assume all risk from the use of any of the information in this article.


Many readers over the years have asked about coverting their Macs to use a PC ATX case for reasons of low cost and increased drive bays (internal and external). A few readers have noted they've done this, but Dan Calhoun was nice enough to send some photos and info on his 8500/ATX converted system. Here's Dan's comments on the project:

" Mike,
I wanted to send this message regarding the little photo shoot on my Macinstein. This unit is sort of a backup to my main 8500. This is running an ATX power supply since it's birth. I put in a 300 watt PC Power and Cooling unit which came with an extra plug full of +3.3v leads which are needed with the 8500. I use an INWIN 500 ATX case which as you can see has room for 3 5-1/4" drives, a floppy, and I really can't say how many [internal] 3.5" you could get into it but my main unit I use now has 4 inside. 3 SCSI and 1 EIDE. This has been my 4th unit that I have built like this. I like the room in the case. The backplate is just a simple aluminum plate which I have milled the appropriate holes for I/O access. It's very simple to do.

The motherboard (MB) is attached on standard PC style lugs that are available at any darkside shop. Obviously the PC MB's holes and the macs are worlds apart so the backplate is made first, then the MB is placed on the tray and the holes spotted and then drilled. I can get the MB out of the box in less than 45 seconds if I need to and I can even change or access most of the ram without removal.

The small circuit board attached to the PS loom is an inverter circuit that was designed by an engineer in Germany who has also likes to tinker. The circuit allows the ATX supply to function with soft power on just as the MAC's PS does. Keyboard SW for ON and software OFF. This has been working for well over a year without any problem. I'll include some jpegs of the circuit and explanation [See images below]. The only real hassle with the ATX supply is that it doesn't have the correct amount of +5 volt leads or Grounds. These have to be split to accommodate the macs power requirements. The PC supply uses a 20 pin Molex connector and the Mac uses a 22 pin Molex (minifit jr) which are hens teeth to find and I had to buy min. of a hundred to get a handful. I have plenty to sell at my cost. The connector contacts are available at Jameco Electronics they're for the PC ATX connector. It can be done and it works OK. The PS supplies for the ATX even at the best possible quality are 1/2 the price of what mac is selling for. [The best quality ATX power supplies I've ever used are from PC Power & Cooling -Mike]

The unit is running a 604-200 processor.
My other 8500 has a XLR8, ZIF G3-350, Orange Micro Firewire Card, 4 gig VST Drive, Turbomax EIDE 33 Card, 13.6 Maxtor, 7200 rpm drive.

PS: Apples Drive Setup refused to initialize this drive, FWB mounted it but could launch it when it was a full simple volume, (froze when the HD icons appeared) this evening I went to Intech Software, www.intechusa.com paid my money and downloaded their drivers and Bingo it's working. Their HD software found it , formatted HFS +, and I tested it. I'm impressed. They're speed test indicated a 12.5 MB throughput, hey its faster than macs narrow SCSI internal at 10.. I'm happy..

Dan Calhoun
Rio Linda,CA "

ATX_inverter ATX_Power_Adapter Back Front MBoard
ATX Inverter ATX Power Adapter Back View Front View Motherboard
PC-MAC_PS_pinouts Side Top Tray_Out2 Motherboard_on_ATX_Tray
PC-MAC PS pinouts Side View Top View Tray Out 2 MB on ATX Tray.

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