Re: Wow! Is memory ever cheap!

[H. Peter Anvin]

Larry McVoy wrote:
> > >
> > > On the other hand, if your apps don't have built in integrity checks then
> > > ECC is pretty much a requirement.
> >
> > Isn't this pretty much saying "if you're willing to dedicate your
> > system to running nothing but Bitkeeper, you can run it really fast?"
> 
> A) Fast has nothing to do with it, ECC runs at the same speed as non-ECC;

"It" meaning BitKeeper.

> B) As I said above, "if your apps don't have built in integrity checks then
>    ECC is pretty much a requirement";
> C) As I said above, we use our systems for BK development, so this choice
>    makes sense for us.
> 
> I think the point you are really missing is that it is not an either/or
> choice.  All you really need in practice is one application which is
> both heavily used and has integrity checks.  It could be BitKeeper or
> something else, all that matters is that it will detect memory problems.

This is not true in my experience.  YES, it will detect bad memory
configurations, but with over 2^34 memory cells to worry about -- each of
them carrying a charge of a few dozen electrons only -- you WILL have
random failures, especially if the memory is allowed to remain stale for
extended periods of time, as is very likely in a configuration like this
(think disk cache.)

Bad memory configurations is bad.  However, good memory configurations
are not necessarily perfect.

	-hpa

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