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

Austin T. austhomp at iastate.edu
Sun Jul 6 19:59:36 EDT 1997


At 01:23 PM 7/6/97 -0600, you wrote:
>
<snip>
>	I have a concern about increasing the proportion of clients
>running on overclocked machines; possibly due to my ignorance of the
>overclocking experience.  
<snip>
>	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
>

That is a very honest concern, and in fact what you are supposed to do,
according to Tom's Hardware Page, is to run rigorous tests on it to see if
it is stable.  This includes many benchmark/testing programs such as
winstone 97.  Depending on what you are doing, you can be as rigorous as
you want, it's basically "burning in" you computer again to find any
problems.  Also, Windows 95 itself is a pretty good detector for these
errors, while you may play in Dos and Dos games at really high speeds,
Windows might not so eliquently tell you that it just isn't going to happen.  

Personally, I have had no errors besides one I accidentally caused myself
since I overclocked my cpu.  I tried a few other combinations, and my 133
running at 150 and 166 were quite stable too.  For kicks I tried 225 (3 *
75), and no go, so I upped the voltage from STD to VRE (I think that's
it...) and it worked, but my video card didn't want to run at the higher
PCI bus speed.  That's another potential problem with overclocking, cards
not up to the more performance.  Also the memory must be up to it too,
since if it is, it runs faster (well, when you up the bus speed that is).

Right now I'm contemplating whether 187.5 is too much for my 133 right
now..it's just a little hotter than 166, and 150 is barely noticable as per
change in temp.  

I read somewhere (I might still have the book) that Intel (allegedly) makes
all the classic pentiums from one dye (sp?) and then tests them, marking
each one with the speed it is capable of.  Well, it goes on to point out
that, if there is more demand for slower chips and the supply of slower
chips runs out, they will just mark higher performing chips as that slower
speed, therefore never executing at full potential.  This is why not every
cpu can successfully be overclocked, some are really only capable of that
speed, and some are better, but there happened to be more demand for that
slower speed.

Well, I hope that I wasn't too far off of the truth and that this might
give a little more info about overclocking and it's use in reliable
computing.  If any one else has more to add, I'd love to hear your
opinions/ideas/pointing-out-my-errors.

Austin


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Austin Thompson     <austhomp at iastate.edu>  \
                                            |
http://www.public.iastate.edu/~austhomp/    /
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