John, Apologies, I keep on forgetting that the '8' just signals the above the line, you and Tom and all the others are quite correct with the x'7fffffff', I have it now... it is a pitty that IBM did not use the lowest bit to signal the line... x'00000001' for 24-bit and x'00000002' for 32-bit, it would have meant less wastage. Because you would have lost the first few addresses... Wonder what the affect of that would have been on all the programs that that branch to x'0' when they go hey-wire...
One more question, does this apply to real storage too, or has IBM found a different way of managing this? Regards Herbie -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Chase, John Sent: 07 November 2007 17:56 To: [email protected] Subject: Re: CSA 'above the bar' > -----Original Message----- > From: IBM Mainframe Discussion List On Behalf Of Van Dalsen, Herbie > > John, > > That makes no sense to me... I thought that a 31-bit program > could address x'00000000' -> 'x'0FFFFFFF' below the line, and > the same above the line. I.O.W. it could go up to x'8FFFFFFF' > which means x'0FFFFFFF' > above ? This means that the hole is from x'00000000 90000000' -> ? A 31-bit program can address from x'00000000' through x'7FFFFFFF'. Expressed in 64-bit addressing, that range is from x'00000000_00000000' through x'00000000_7FFFFFFF'. IOW, for a 31-bit program, the "high halves" of the 64-bit registers do not exist; they may actually contain "anything" and they will be ignored by 31-bit (and 24-bit) programs. A 64-bit program (amode 64) can address exactly the same range, in the same way, except that the "high halves" of the 64-bit registers MUST contain all binary zeroes. IN ADDITION, an amode 64 program can address from x'00000001_00000000' through x'FFFFFFFF_FFFFFFFF'. NO PROGRAM is allowed to address the space from x'00000000_80000000' through x'00000000_FFFFFFFF', which is the "bar", the "hole", or whatever other name seems appropriate. See previous posts from Ed Jaffe, Peter Relson and Chris Craddock for why that is a "good idea". -jc- ---------------------------------------------------------------------- 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 Elavon Financial Services Limited Registered in Ireland: Number 418442 Registered Office: Block E, 1st Floor, Cherrywood Business Park, Loughlinstown, Co. Dublin, Ireland Directors: Robert Abele (USA), John Collins, Terrance Dolan (USA), Pamela Joseph (USA), Declan Lynch, John McNally, Malcolm Towlson Elavon Financial Services Limited, trading as Elavon, is regulated by the Financial Regulator ---------------------------------------------------------------------- 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
