INFO WORLD, May 11, 1987 Page 5 Incompatibility of Disk Drives, Controller Puzzles Makers By Mark Brownstein A mysterious problem with combining either of two Seagate 20-megabyte hard disk drives with an Adaptec disk controller renders the combination unusable, according to Adaptec. The problems seem to be encountered when a Seagate 225 or 238R drive is paired with Adaptec's 2070 RLL controller, according to Russell Stern, Marketing Manager for Personal Computer Products at Adaptec. The control- ler is used to increase the capacity of the drive to 30 megabytes by using run length limited encoding. The problem was originally reported by users whose drives became unusable months after being set up to work with RLL controller cards, Stern said. Tovar, a value-added reseller in Laguna Hills, California, has experienced a 25-percent failure rate with the 238 drive and the control- ler, and a 20- to 25-percent failure rate when the 225 drive is paired with the card, according to Ken Hull, in-store representative. According to Stern, Adaptec has been working closely with Seagate to isolate the problems, but for the present no one is sure what that problem is. Neither company feels that the problem is related to its own products. Seagate has not certified the Seagate 225 drive to be compatible with RLL controllers, according to Al Shugart, chairman and chief executive officer of the company. But the 238R drive is certified, and was designed to be used with approved RLL controllers, of which the Adaptec 2070 is one, Shugart said. Tovar, which uses Adaptec controllers exclusively, has not experienced the failures when using non-Seagate drives with the controller, Hull said. But the Seagate drives also seem to work well with other RLL control- lers, said Paul Mace, president of Paul Mace Software, which sells a utility to evaluate hard disk performance. "We've heard of the problem only when the drive is used with an Adaptec controller, not an OMTI or a Western Digital," he said.