Macintosh LC 475

   

The Macintosh IIfx

The IIfx is an interesting machine, well ahead of its time.

Originally developed under a contract for the US military, who had a requirement for a UNIX workstation, The IIfx was first sold in March 1990 and production lasted until April 1992.

Due to the demanding specifications and generous budget of the contract, the IIfx has some fairly unique hardware features. Firstly, it has a 40 MHz 32-bit clean 68030 Motorola processor with a 68882 FPU, which was considered amazing at the time, the best most PC's could manage was between 10 and 25 MHz on x86 processors. This 68K processor sits on a 40MHz bus, which was the fastest Apple would produce until the 68040 based Quadra 840av in 1993.

In addition to having such a powerful Central Processor, the IIfx has two MOS 6502 10 MHz ASIC chips. These are used to handle disc access, serial ports and ADB devices such as the mouse and keyboard. This reduces the load on the CPU and allows it to process other tasks. This enhancement and many others were implemented in hardware, but never supported by Apple in the Mac OS :(

The IIfx uses 64-pin SIMMs. This type of RAM was not used on any other computer as far as I know. Some IIfx's have 9 bit parity RAM, which can be identified by a parity chip present on the logic board. Also, a parity IIfx will have 9-chip 64-Pin SIMMs installed. I believe that parity was an option that could be specified when you ordered your IIfx, but I have *never* seen one, nor heard of anybody who knew anyone that once saw one!

Storage

The IIfx can support any SCSI-2 Hard Disk that will fit in the case! SCSI-2 hard disks are those with 50-pin connections. Try searching eBay for "SCSI 2" or "50 pin SCSI". You should be able to pick up a 3 or 4 GB SCSI hard disk for about £15 including S&H.

I decided to replace my IIfx's once top of the line 160 MB hard disk with a Seagate 2.1 GB unit that I had. The first obvious problem is that the IIfx was designed to accept 5.75 inch drives and the new drive was a 3.5 inch drive. Not a problem, there are mounting kits available to convert the fittings for a 3.5 inch drive to those for a 5.75 inch drive. I chose to make my own from a sheet of aluminium.

My home made adapter allows the drive to sit on the 'platform' where the original drive once sat. I suppose that you could add a second drive in the location designed for a second floppy drive. This would need a power cable splitter and a long 3 headed SCSI cable. I have never tried this!

OK, so you've installed the new drive. Presumably it has no Mac OS on it and is not formatted or partitioned in a way your Mac can understand. You'll be needing Apple's 'Apple HD SC Setup'. If you bought an Apple hard disk the one on your 'Disk Tools' disk will do just fine. If you bought a drive that's not supported by apple, then HD SC Setup will moan that no suitable devices were found. Don't worry! Apple released a version of HD SC Setup that didn't care what type of drive you have, it shipped with A/UX. Download it here.

Looking inside the IIfx

The IIfx is pretty easy to work on inside. The case seems to have been built to survive a small explosion. I've inluded some pictures just incase you're curious as to what the inside looks like :-)

1. Remove the screw from the back of the case.

2. Press in the catches and lift up the top of the case:

3. Carefully hinge the lid toward the front of the unit taking great care not to damage the plastic fastenings along the front edge:

4. Lift the lid away and turn the case so the front is facing you. Remove the 4 screws indicated by red dots:

5. Pick up the platform with the hard disk and floppy drive(s) and set it down a few centimetres to the right so that it rests on the edge of the case. Now disconnect the hard disk's power and SCSI cables, and also the floppy drive(s) cable.

6. That's it, now you can gain access to the components on the Logic Board.