[email protected] (R.S.) writes: > Yes and no. > It depends on definition of "real CKD device". > Actually 3390 and 3380 were FBA under the cover. The "data cells" (32 > or 34 bytes) were the fixed size sectors. Indeed, the device was not > emulated - physical disc was presented as single I/O device, but the > elecronics hidden the cells from MVS view. > > AFAIK the last "fully real" CKD device was 3350 (1975 GA).
re: http://www.garlic.com/~lynn/2012b.html#58 Why can't the track format be changed? 3380/3390 were the low-level emulation on kind of FBA. One of the things was that 3380 was the high-end datacenter disks and the only mid-range disks were FBA. In the 3380/3370 time-frame there was huge explosion in new 4300 sales going into non-datacenter environments ... which MVS was precluded from because of lack of FBA support. Eventually, trying to provide MVS with an entry into that market ... 3375 was created ... that was a 3370 under the covers. The other problem was that many of these environments were getting close to set-it and forget it ... requiring very little care&feeding ... which tended to also preclude MVS. misc. past posts mentioning CKD, multi-track seek, FBA, etc http://www.garlic.com/~lynn/submain.html#dasd misc. old email mentioning 4300s ... some of which involve 3380/3370 http://www.garlic.com/~lynn/lhwemail.html#43xx past posts about them letting me play disk engineer in bldgs. 14&15 http://www.garlic.com/~lynn/subtopic.html#disk -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
