In a message dated 8/6/2005 9:35:55 P.M. Central Daylight Time, [EMAIL PROTECTED] writes: >real CKD DASD haven't been available for decades...
IBM stopped manufacturing 3390 disks about five years ago, I believe, which was much more recent than decades. The 3390 disk is a CKD DASD. What is written on disk tracks is CKD - Count, Key, Data. The E (Extended) part of ECKD had nothing to do with what was written on the tracks, and was a set of new commands for communicating the description of CKD blocks on the tracks to the control unit. All new control units since the early 1980s have been ECKD control units, but the disk devices themselves were always CKD until IBM stopped making 3390s. Now all real disks are Fixed Block Architecture (FBA) and control units map CKD into FBA for writes and FBA back into CKD for read operations. Bill Fairchild ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
