On Thu, 27 Jul 2006 19:17:00 +0000 "Jeffrey D. Smith" <[EMAIL PROTECTED]> wrote:
:>From: "Edward Jaffe" <[EMAIL PROTECTED]> :>Sent: 7/27/2006 1:13 PM :>To: "[email protected]" <[email protected]> :>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. :>Alright, we agree to disagree on the interpretation. Anybody from IBM willing to give the official answer? -- Binyamin Dissen <[EMAIL PROTECTED]> http://www.dissensoftware.com Director, Dissen Software, Bar & Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. I very rarely bother responding to challenge/response systems, especially those from irresponsible companies. ---------------------------------------------------------------------- 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
