================================================= -----Original Message----- From: "Edward Jaffe" <[EMAIL PROTECTED]> Sent: 7/27/2006 1:13 PM To: "IBM-MAIN@BAMA.UA.EDU" <IBM-MAIN@BAMA.UA.EDU> Subject: Re: Doing a LM of two words on a double word bounday - is it serialized?
Jeffrey D. Smith wrote: > Just back-up a bit in the PoPs and read the "Block-Concurrent > References" paragraph. It all depends on the size of the block. > All CPU must be using the same block-size to ensure consistent > views. A full-word block is not the same as a double-word block. > The full-word store-type access is not necessarily "widened" to > a double-word access (or quad-word on Z machines). The CPU must > be using the same alignment and block width. The PoPs does not > say that different accesses to different block sizes is concurrent. > > The full-word store is not a double-word concurrent store. Therefore > the double-word fetch is not protected from inconsistent results. > The block sizes are different. The specification only applies to > the same block access (alignment and width). > Huh???! That paragraph in PoOps says: "When a fetch-type reference is specified to appear to be concurrent within a block, no store access to the block by another CPU is permitted during the time that bytes contained in the block are being fetched." This statement is simple, not complex. It says, without caveats or exceptional language of any kind, that the (entire) block is protected from being updated by other CPUs until the block-concurrent fetch is complete. It does not stipulate that another CPU's store access must be on the same block boundary/width in order to be delayed. -- Edward E Jaffe ================================================= Alright, we agree to disagree on the interpretation. Good luck. Jeffrey D. Smith Farsight Systems Corporation 24 BURLINGTON DR LONGMONT, CO 80501 303-774-9381 direct 303-709-8153 cell 303-484-6170 fax ---------------------------------------------------------------------- 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
