From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Mohammad Khan Sent: Friday, March 27, 2009 9:07 AM To: [email protected] Subject: Re: "A foolish consistancy" or "3390 cyl/track architecture"
>Please forgive my ignorance but how does robbing Hs to pay Cs increase the total addressable storage ? Unless off course those Hs were for show only. Mohammad Those Hs were for show only. The Hs that are now robbed used to be unused and always had to contain zero. For at least the last 25 years, all new DASDs from IBM have had 15 tracks per cylinder. Long, long ago there were some DASDs with more or fewer, but now the number seems fixed for all time at 15. Thus there are 12 bits (3 Hs) that are available for use for some other purpose, assuming that microcode and software can tell when the Hs bits really mean high-order cylinder numbers and when they don't. Bill Fairchild Rocket Software ---------------------------------------------------------------------- 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
