CompuServe Messages

The Seagate 225 is a 20 MEG MFM (non-RLL) HD. The Seagate 238 is the RLL version of the above. The Okidata 526 is the equivalent of the Seagate 238 with 10% more disk Capacity. (By the way, the Oki is faster than the Seagate. Both are 65 msec. drives, but the Oki seems to have better electroincs to move the data faster into the Adaptec.) General info: MFM refers to a method of putting data on a HD. RLL is a different method that packs approx 1.5 times as much data on the same HD (ie. a 20 meg drive becomes a 30 meg with RLL encoding). Most drives will work as RLL even though they are not `certified' as RLL drives, but using drives that way will cause a lot of data-loss later on because the media (disk surface) simply is not good enough. Seagate, for example, tests most all of their 20 meg drives for RLL, those that pass become Seagate 238's those that don't wind up as Seagate 225's. RLL encoding requires that the media be able to store 1.5 times the data normally stored, and (just as importantly) that the electronics in the drive be able to pass the data at 1.5 times the normal speed. All in all this is a very demanding requirement.