identifying PC Simms

On 9/30/05, Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote: It's one of those things that has changed. Prior to around the Penitum introduction, the vast majority of PC's (and most serious machines) used parity by default. Parity could be switched off (usually by DIP switch or mobo jumper.) As memories got bigger, parity errors due to random events (cosmic ray, decay of radio active potassium in the chip ceramic) went from being a once a year thing, to being a once a day thing. Of course, the users whose computers crashed with a "parity error" message on the screen got annoyed and blamed the motherboard manufacturers. The manufacturers came up with two solutions. The first was ECC/EDAC support, which could correct most of the errors. The second (and cheaper) method was to not use parity at all. After all, 11% of parity errors aren't actually a problem in the RAM the computer sees. Of the rest, a significant fraction affect memory areas that won't be saved to disk. If you corrupt code in memory a program will probably crash (rather than the computer), at which point the code will be reloaded from memory. Other likely places for memory errors are big images. Chances are that the errors won't make to disk. I've often wondered if any operating systems wash their pages. Having the idle loop perform a quick checksum on pages that aren't dirty to see if they are intact (and reload them from disk if they aren't) would seem like a good idea on non-ECC systems. Eric