Re: Computer Flake Outs (was: Re: On Overclocking - READ THIS!)

Rodney R. Korte (rrk102@psu.edu)
Wed, 07 May 97 09:26:57 -0400


On Wed, 7 May 1997 00:58:58 -0400 (EDT), Justin Dolske wrote:

>On Tue, 6 May 1997, Rodney R. Korte wrote:
>
>> It claimed something like one one-bit error every 4-6 months for
>> the average Pentium-class computer with 32MB
>[...]
>> The memory footprint of DESCHAL5 on my machine is about 1/2 MB,
>> so I could expect an error in memory in which the DESCHAL code
>> resides about once in 3 years.
>
>Hmm, don't think so. If you assume a 1 bit error in a 32meg core every 4
>months, you should expect a 1 bit error in any particular .5meg region
>every 21 years (it's 1/64th the size). With 6000 clients, this would
>correspond to a single bit error every 3 or 4 days.

Yes, you are correct. I was working off powers of 2. It was late. ;-)

>I've no idea how useful this number really is. You've also got to factor
>in the probability of it being detected (by parity or the program
>crashing), and the probability that it won't affect the actual
>calculation (ie, an error in non-essential code, an unused bit on the

Yup, I mentioed that.

>stack, etc). Then there's the issue of cache. If most of the code is
>sitting in cache, you'd have to figure error rates for it (which are
>probably different, due to SRAM vs DRAM), and the probability that the
>error will affect stale or expired cache entries.

Again, all true, and that's why it was a rough calc. However, I
don't think the cache would have and impact on the memory- it's
still memory and most folks have 256k or 512k.

>> Fortunately, I have parity memory
>
>Are you sure it's real parity? For awhile, memory with pseudo-parity was
>being sold, where the "parity" bit was generated on the SIMM to correspond
>to what the DRAMs currently held when accessed, so there was really no
>error correction. :-)

It's real. I don't go for cheap HW. And that's also why I don't
have HW problems like most folks.

Rod

--
Rodney R. Korte                   OS/2. Operate at a higher level.
korte@sabine.acs.psu.edu    ---> MIME, PGP (finger for key) welcome.
http://sharkbait.arl.psu.edu/

Crack DES NOW! http://www.frii.com/~rcv/deschall.htm