On Oct 9, 2008, at 12:26 PM, Dan wrote:
> Because Apple doesn't use ECC,,, that means your > data in the older system was foo -- And you never knew it until the > crash hit! Apple used parity in its ill-fated Apple Network Server. With parity, a single-bit error can be detected, but not corrected. Parity was not mandated, however, and if "legacy" EDO/FPM was installed in ANY RAM position, parity was turned off for all of RAM. Apple later used ECC in its G5s. With many implementations of ECC, every single-bit error can be detected AND corrected, while every double-bit errors can be detected none of these can be corrected. With modern implementations of ECC, many double-bit errors can be both detected and corrected, while every single-bit errors can be both detected and corrected. With the most modern implementations of ECC, every double-bit error can be both detected and corrected. At the large mainframe manufacturer where I was formerly employed as an engineer, we developed and patented an ECC system which combined parity and ECC, thereby using fewer total detection and correction bits than was formerly required. This implementation utilized the fact, imposed upon it by the instruction architecture and the Principles of Operation, that results could be 8 bits, 16 bits or 32 bits (and addresses could be 24 bits), so that parity was required, anyway, to cover the 8-bit case, and one might as well intelligently combine parity and ECC. As a consequence, we were able to get ECC down to significantly fewer bits than our competitors. With our implementation, even so-called "intermediate" results were covered by at least parity, even with in the execution units themselves. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
