Photo: Red Hill.
Miniscribe 8438 and 8425
An interesting pair of drives, identical except for the badge. Miniscribe was Seagate's biggest competitor for the mass market during the late eighties and the 8425/8438 twins were a major part of Miniscribe's quest for overall market leadership. They sold in vast numbers.
The 8438 was a neat, modern looking 3.5 inch 30MB stepper drive with factory-certified RLL capacity. The 8425 was the exact same drive without the certification. In practice, Miniscribe mass-produced drives and then tested them. The very best units were sold as higher-value 8438s, the also-rans as cheaper 8425s. Of course, there was nothing to stop you buying a 20MB 8425 and putting it with an RLL controller to get 30MB — except that it wasn't terribly likely to be reliable - otherwise Miniscribe would have marked it as an 8438 in the first place.
We used to do the reverse sometimes: buy an 8438 and put it on a low-density MFM controller to make a very reliable 20MB drive system. It cost a bit more but because the 8438 was RLL certified, we already knew it was a particularly good drive, and by running it on an MFM controller we had a huge margin of safety. I can't remember ever seeing one of these under-stressed 8438s fail. Though we still saw working ST-225s from time to time up until the end of the century, we stopped meeting the 8438/8425 twins in working systems long before that.
By the way, these were one of the earlier 3½ inch drives to become common. Notice that the modest-looking capacity per platter is actually quite high when you consider that the discs are much smaller than was common at the time.
|Performance||0.16 or 0.20||Reliability||AA2|
|Data rate||5 or 7.5 Mbit/sec||Spin rate||3600 RPM|
|Platter capacity||10.7MB or 16.45MB||Heads||2 or 4|
|AT drive type||2||Form||3.5" half-height|