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From: perley@trub.steinmetz (Donald P Perley)
Newsgroups: comp.lsi,comp.arch
Subject: Re: predicted yield of BIG microprocessors
Message-ID: <13481@steinmetz.ge.com>
Date: 29 Mar 89 16:36:02 GMT
References: <15878@obiwan.mips.COM>
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Reply-To: perley@trub.steinmetz.ge.com (Donald P Perley)
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In article <15878@obiwan.mips.COM> mark@mips.COM (Mark G. Johnson) writes:
>
>
>	What yield is *NOT* good for, is estimating product cost.  It
>	only measures die cost.  To that you must add test cost(s),
>	burn-in cost, depreciation on the $100M fab, depreciation on
>	the array of $5M testers, package cost, QA and Reliability
>	screen costs, design cost, and so forth.  Particularly for
>	microprocessors, die cost is a *negligible* fraction of
>	selling price.

Many of the additions you list are dependant on the number of dice made,
but have to be ammortized over the number sold (the good ones), so 
yield is significant, at least far as fab line and tester ammortization
is concerned.

The cost of a good die includes what it cost to send its share of bad
ones throught the fab, and the bad ones still get tested.