On 11/28/2012 12:39 PM, John Gilmore wrote:
I must, however, add that "unpredictable" is sometimes in some IBM publications used as a polite euphemism for "It's too complicated to explain here, and you wouldn't understand anyway".
Sometimes they do that because they get pressured to retrofit a cool new instruction back to an older model and there is no way to make the older model work "correctly". For example, it used to be undefined which space instructions were fetched from while in cross-memory mode. The logical choice was "primary" (and the hardware designers knew that) but they were unable to make it work on the older processor to which the function was being retrofit. We (software developers) suffered for at least a decade with that ugly restriction.
-- Edward E Jaffe Phoenix Software International, Inc 831 Parkview Drive North El Segundo, CA 90245 http://www.phoenixsoftware.com/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
