[rc5] Overclocking (wasRe: [rc5] Another approach)

Richard Ebling rebling at xmission.com
Sun Jul 6 14:23:53 EDT 1997



On Sat, 5 Jul 1997, Del Conte wrote:
: I like your train of thought.  We need as many clients as possible.  As I
: was thinking about where we can get these clients from I thought of two
: different places/groups of people. [alt.2600 suggestion bobbitted]
: 
: Another group of computer people who are into speed are overclockers.
: These people run their cpu's at speeds higher than recommended (including
: me).  This means that their performance would be dramatically increased.
: The best place I know of is sysdoc.pair.com.  If we talked to the owner of
: this page he may help us out a bit.

	I have a concern about increasing the proportion of clients
running on overclocked machines; possibly due to my ignorance of the
overclocking experience.  

	My impression is that nominal chip/processor speeds are based
upon the speed at which that particular component is known to run
_reliably_, i.e., without errors.  And that practically any chip _can_
run at a faster speed (i.e., boot up, respond to instructions, output
results), but that there is a point (probably based on increasing
internal temperatures) at which errors start to occur.  These errors may
or may not be detectable by the user.  The computer itself can't tell
which numbers are accurate and which are bogus, and merrily rolls along,
like the original Pentinum chip with FDIV problems, until enough
problematic errors occur, that the machine crashes/turns pink/writes
Hamlet.  Overclockers tolerate this risk because the speed increase of
10+ % outweighs the negligible risk of a crash or undetected
errors (Screen goes gray? Reboot, BFD).

	However, in other contexts, accuracy and reliability of results
is important.  If I were in charge of an expensive, time-consuming
project, I would either use the most reliable equipment available to do
the processing--or use faster, less-reliable equipment to do the
processing TWICE (on the notion that squaring the small probability of
heat-related errors generates sufficient certainty).  Any numbers on
reliability of overclocked processors? Even a 1-in-a-trillion
probability of undetected errors could render uncertain a significant
number of potential keys. 

	- Richard "Let's go through 2^56 keys.  Twice!" Ebling


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