[CUBE] ECC when it come to memory

[Robert W. Bumala]

I believe you're thinking of EDAC (Error Detection and Correction).  We 
use that for RAM that's exposed to a high radiation environment, such as 
space.  Normal EEC RAM just has a parity bit, and most IBM Wintel 
machines use it.  Way back when about 5 BM (Before Macintosh), IBM 
decided that the DRAM memory needed a parity bit to detect errors.  It 
didn't fix errors, just crashed the machine with a parity error.  Apple 
figured that if the memory was bad it'd crash all by itself, they didn't 
need a parity bit.  This is why when you buy memory for a Mac, it has a 
missing chip, that's the parity bit.  It's fairly useless, but wintel 
machines still use it for some odd reason.  People in the IBM-like world 
jump through all kinds of hurdles to maintain compatibility with an old 
obsolete architecture.  That's why they lived with the dreaded 1 
megabyte limit for so long.
Bob.

Rick Rodman wrote:
> Actually, ECC usually uses about 5 additional bits per byte of memory.  
> A simple parity bit is insufficient.  This memory is, as was mentioned, 
> usually used only in servers.
> 
> On Sunday, August 17, 2003, at 01:26 PM, Alan Thompson wrote:
> 
>> ha haaa - now that i see your reply, i see that i'm not the only one 
>> that couldn't remember what the second c stands for :)
>>
>>
>> On Sunday, August 17, 2003, at 08:14 AM, Steve Goldstein wrote:
>>
>>> Error Correcting something-or-other [Code (?)]
>>>
>>
>>
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-- 
----------------------

Robert W. Bumala
Circuit Design Engineer Specialist
Lockheed Martin Advanced Technology Center

Lockheed Martin Space Systems Company
Org. L9-42  Bld. 255
3251 Hanover Street
Palo Alto, CA 94304-1191

Phone: (650) 354-5918
Fax:      (650) 424-3333
EMail: Robert.W.Bumala at lmco.com