Greg A. Woods wrote:
| 
| [ On Sun, February 1, 1998 at 20:59:28 (-0500), David Jones wrote: ]
| > Subject: Re: VIA VP2 chipset
| >
| > Why do you need ECC?
| 
| The question is more like:  Why would you ever *not* want ECC?????
| 
| With memory densities as high as they are, and prices as low as they
| are, not using ECC, even in a clean-room environment, is, IMHO, insane.
| Soon a single alpha-particle might knock out many bits simultaneously
| instead of just one.

This is unlikely.

To guard against alpha particle upset, a modern DRAM cell today is designed
to have a capacitance of 25-30 fF.  This is regarded as the minimum required
to maintain alpha particle upset immunity.

Although the surface area of the DRAM cells is getting smaller, other things
are changing too.  Dielectric thickness is going down, thereby increasing
capacitance.  New dielectrics with higher dielectric constant are also
being developed.

The primary source of alpha particles in early DRAM chips was the package
itself - ceramic being worse than plastic.  New packaging technologies that
start with better materials reduce that source too.  It does not help your
alpha particle immunity if the chips are used in a "clean room".