Path: utzoo!attcan!uunet!lll-winken!lll-lcc!pyramid!amdcad!rpw3
From: rpw3@amdcad.AMD.COM (Rob Warnock)
Newsgroups: comp.arch
Subject: Re: CAM hits the market
Message-ID: <23791@amdcad.AMD.COM>
Date: 16 Dec 88 07:19:25 GMT
References: <9809@obiwan.mips.COM>
Reply-To: rpw3@amdcad.UUCP (Rob Warnock)
Organization: [Consultant] San Mateo, CA
Lines: 20

Based on the announced characteristics, I suspect the Am99C10 CAM is intended
for applications like MAC-level bridges (note the "selectable 16- or 48-bit").
For that application, 100ns is fine -- even for FDDI. Even with clever hashing,
or tree-structured direct-mapping, it'll take a fast node CPU several
microseconds to do the same thing.

But 256 words is marginal. For bridging apps, you basically need a big enough
CAM in each bridge to hold all the source addresses you may ever see on either
side of the bridge -- that is, the number of hosts on your net -- which is why
I said 256 is marginal. But you can cascade them to expand the size. (The chip
is said to include cascade controls.)

So the Am99C10 probably has a place in the world.

Rob Warnock
Systems Architecture Consultant

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