PC Hardware in a Nutshell, Second Edition

Working with FDDs

Keep the following issues in mind when working with FDDs:

Choosing

3.5” HD FDDs are $15 commodity items made by several manufacturers. We prefer the Teac FD235HF, but there is little difference between brands. Buy whatever is offered. 5.25” FDDs are still available new for $40 or so, but that won’t last forever. If you need a 5.25” FDD to rescue data on old disks, get the drive now. If you patronize a local computer store, check there first. They may have a stack of old 5.25” FDDs they’d be happy to give away or sell cheaply.

Installing

5.25” FDDs require a 5.25” half-height, externally accessible drive bay. 3.5” FDDs can be installed in an externally accessible 3.5” third-height bay, or, by using an adapter, in a 5.25” half-height bay. The BIOS automatically detects installed FDDs, but can determine type unambiguously only for 5.25” HD (1.2 MB) FDDs, which spin at 360 RPM rather than 300. For other drive types, older machines assume 360 KB or 720 KB and newer systems assume 1.44 MB. Use BIOS Setup to confirm that the drive type is configured correctly.

Cabling

If you add or replace an FDD, also replace the cable, particularly if it is the original cable. Manufacturers often fold and crimp the FDD cable for improved cable routing and airflow. An old cable that has been so treated is no longer reliable, especially after you disturb it to install the new drive.

Change Line Support

All but the oldest FDD controllers use line 34 for Change Line Support. When the FDD door ...