3.5" 720K disk drives in a Model 4 Computer
As 5-1/4" disks become harder to find and 5-1/4" disk drives that work are even harder to find. Many of our subscribers have changed to 3-1/2" 720K disk drives.
Not only are the double-density 3-1/2" disks fairly easy to acquire, there hard jacket makes them more resistant to damage.
Installing a 3-1/2" dirve is not difficult in a Model 4, for Mod 4s and 4Ps the signal cable will need to be changed and a kit used to fill the space of the 5-1/4" disks. These kits come with a power cable to convert from the large moldex 4 pin connector to the smaller 4 pin power connector on the 3-1/2".
There is no need to change any of your software or operating system disks. Any of the Model III and 4 software boots and operates the 3-1/2" disks. Although you do need to use double-density disks and not the high density 1.44 disks.
Here is a model 4 with four 3-1/2" drives installed.