CD-ROM on the Cheap!

Using an old PC case and power supply to add new expansion potential to an already well-expanded Amiga

By Leo Maxwell, Contributing Writer, hammer@enterprise.net

CD-ROM for your Amiga may seem an expensive proposition, and even with prices dropping as they are, some of you will put off buying one. I know, from personal experience, the pressures that wives and families, obsessed with such luxuries as holidays, roof repairs, redecorating the living room, etc., can exert.

After installing a Viper accelerator card with 4MB of RAM, an external floppy drive, and finally, a 540MB 3.5" hard drive to my trusty A1200, the power supply started to complain (unexpected crashes, dying when reading files, screen blanks, etc.).

As I had picked up an ATAPI CD-ROM at a computer fair, things weren't looking good for its installation to an already stretched system. After investigating the options, I decided that available expansions were beyond my limited funds for the foreseeable future. However, as I am increasingly involved with PC's at work, I investigated the possibility of using a PC power supply.

Fortune smiled on me, and I obtained a defunct 286 compact PC case in exchange for a favour, although it is possible to buy these system units, with a 220 Watt PSU and cooling fan, for £20 or less.

Total cost of the hardware required was less than £55, for which I have gained a higher-rated PSU, a four speed CD-ROM, and a system case which makes a good monitor stand, so that no more desk space is needed.


****IMPORTANT!!****

PLEASE NOTE!

I CANNOT ACCEPT ANY RESPONSIBILITY WHATSOEVER FOR ANY DAMAGE OR INJURY RESULTING TO ANY EQUIPMENT OR PERSON FROM READING THIS ARTICLE OR FOLLOWING ANY INSTRUCTIONS HEREIN. I ADVISE THAT ONLY COMPETENT PERSONS CARRY OUT ANY PROCEDURE IN THIS ARTICLE.

****IMPORTANT!!****


Requirements:

First Steps

Fitting the CD-ROM into the system unit is a doddle. Remove the case top, and fit the CD-ROM into any empty drive bay. Some cases will need rails to be fitted to the side of the unit, but more recent ones just have screw fixings.

If you have a 3.5" IDE Hard Drive, I strongly advise you to fit this also into one of the drive bays (you will probably need mounting brackets for this). Then just plug in the power connectors and the data cables.

Connecting Up Power

The power cables are the thick cables with four pin connectors at the end. Connect these into the socket on the back of the CD-ROM (and 3.5" Hard Drive, if you have one). They cannot usually be connected wrongly.

Connecting Up Data

Usually you will have a long 40-way ribbon cable with two or three male 40-way connectors with the case. One end normally connects to the motherboard of the PC, and the others to the hard drive and CD-ROM (not to be confused with the 34-way floppy ribbon cable). This is what you will have to modify.

To modify the long cable with the three connectors, you will need to cut off the connector from one end, and fit a new, female connector. This is not as hard as it looks. First thread the ribbon cable between the top and bottom halves of the IDC socket, ensuring that the individual wires of the ribbon are lined up with the IDC pins, and then carefully squeeze the two halves together (a vice is an ideal tool to do this). The teeth on the socket will bite through the insulation on the ribbon, and make contact with the cores inside.

The ribbon cables should be connected to the drives with the marked or labelled edge closest to Pin 1 on the drive PCB (these are often keyed to prevent incorrect insertion). Pin 1 is usually marked on the drive PCB. CD-ROM's are usually configured as slave devices, and the Amiga sees them as a second IDE drive, with the Hard Drive on the same ribbon cable being the Master.

Connection to the Amiga was more involved, but not overtaxing. The Amiga uses the standard IDE interface, except that, due to lack of space, the designers decided to use the 44-pin connector designed for 2.5" drives (commonly used in PC laptops ). The extra four pins are used to connect power, whereas the standard drive has a separate power cable.

If, like me, you bought a 3.5" drive from an Amiga dealer, you will already have the correct adapter cable. If not, you will have to purchase one.

First, I fed the ribbon cable provided with the 3½" drive out between the two halves of the casing at the rear, cutting back the edges slightly with a sharp knife to stop the cable being pinched, and I was then able to connect it to the female socket on the PC cable.

Power Supply Connections

If you wish, you can connect the Amiga power cable to the PC PSU. This enables you to switch everything on with one switch.


****IMPORTANT!!****

NOTE!

THESE ARE THE MOST COMMON COLOURS, AND I HAVE CHECKED SEVERAL DIFFERENT MAKES OF PC, AND POWER SUPPLIES FROM 2 A1200'S, AN A600, AND AN A500, BUT I CANNOT GUARANTEE THAT THEY ARE ALWAYS USED BY ALL MANUFACTURERS. I STRONGLY ADVISE YOU TO CHECK WITH A VOLTMETER FIRST.

****IMPORTANT!!****


The PC PSU will usually have two multipin connectors (sometimes marked P8 and P9).

These are normally connected to the motherboard. As the motherboard was redundant, I cut the required ones and connected the Amiga power cable to them with a standard "chocolate block" connector strip, leaving the other wires connected to the connectors, and thus insulated.

AMIGA
PC
VOLTAGE
ColourPinColourPin-
Brown1Yellow3+12VDC
Black2Black5Signal Ground
Red3Red10+ 5VDC
Shield4PSU Casing
-
Ground
White5Blue4-12VDC

The accompanying pictures, Top View, Side View, and Plugs show the setup and pinouts for the power plugs. (Editor's Note: If you are using IBrowse and have any difficulty viewing these images, set image decoding to "External" in the "HTML Display" section of your IBrowse "Preferences/General..." menu item)


Cost Comparison:

Although I have since read several dire warnings from interface retailers about the dangers of connecting a CD-ROM to the Amiga's unbuffered IDE interface, I have used this setup for nearly a year without any problems.


About me.

Amongst other equipment, I build, commission, and repair PC's (mainly as printservers for Digital Colour Copier Raster Image Processors ), but I still prefer the Amiga's friendly OS to windoze95.

My present Amiga setup is an A1200, 68030 Viper +FPU @28MHz, 10MB RAM, 540MB HD, Matsushita 4X IDE CD-ROM, 1438S, USR 14400 Sportster, and various printers and other bits from work. At the moment, I am trying to get a reluctant 486DX4 @133MHz to share drives with my Amy, so I can use its scanner.

Leo Maxwell, Birmingham UK, <hammer@enterprise.net>