From: "Dave Emery" <die@pig.die.com>
Date: Wed, 28 Dec 94 16:31:47 PST
To: ianf@sydney.sgi.com (Ian Farquhar)
Subject: Re: Are 2048-bit pgp keys really secure ?
In-Reply-To: <9412290859.ZM12937@wiley.sydney.sgi.com>
Message-ID: <9412290031.AA06235@pig.die.com>
MIME-Version: 1.0
Content-Type: text/plain



> 
> A somewhat disturbing trend has appeared in the low-end cost-sensitive PC
> SIMM market.  Some supposedly 9-bit SIMMs are actually 8-bit SIMMs plus
> a parity generator.  This means that the parity checking is essentially
> subverted, because the parity bit is generated from the stored contents
> of memory at read time, rather than the stored contents when it was
> written to.  As such, NO bit errors are detected.
> 
> These SIMMs are almost all being produced in Taiwan, and many have the
> parity generator marked so that the chip appears to be another DRAM.
> It is worth watching out for.
> 
> Why are they doing this?  Well, parity generators are much cheaper than
> the extra DRAM, and so the manufacturers are saving 15-20% on the production
> price.
> 
> 							Ian.
> 
	There is, or was a couple of years ago, another reason for this. 
One of the major SIMM patents is for SIMMs with parity and does not
apply to SIMMs without (a matter of how the claims were phrased), so
companies that don't want to pay royalties to Wang in the US (the owner
of MOST SIMM patents) have used this trick not primarily to cut product
cost but to aviod paying royalties (something like 5%).