NetNews Usenet Archive 1992 #26/NN_1992_26.iso/spool/comp/sys/amiga/misc/16410

Internet Message Format | 1992-11-07 | 2.9 KB

Path: sparky!uunet!comp.vuw.ac.nz!amigans!acheron!alien
From: [e-mail] (Ross Smith)
Newsgroups: comp.sys.amiga.misc
Subject: Re:  Mike Sinz's tests? (was Re: Speeding up the A4000?)
Message-ID: <[e-mail]>
Date: 5 Nov 92 17:20:50 GMT+12
References: <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]>
Distribution: world
Organization: Wanganui Amigans, Wanganui, NZ
Lines: 51

In article <[e-mail]> [e-mail] (Jeff Easton) writes:
>In article <[e-mail]> [e-mail] (Ross Smith) writes:
>
>[ Running chips faster than they are rated]
>
>>Suppose a chip comes in, say, 25 MHz, 33 MHz, and 40 MHz versions. This
>>does *not* mean that the manufacturer actually makes three different chips.
>>They make *one* chip, designed for 40 MHz plus a margin. All chips are
>>tested at 40 MHz; those that pass are sold as 40 MHz chips, those that fail
>>are tested at 33 MHz ... and so on down the line. You end up with four
>>piles of chips :
>>
>>   (1) Passed 40 MHz test; sold as 40 MHz chips.
>>   (2) Failed 40, passed 33; sold as 33 MHz chips.
>>   (3) Failed 40 and 33, passed 25; sold as 25 MHz chips.
>>   (4) Failed 40, 33, and 25; chucked in the garbage disposal.
>>
>>The important point being that, if you buy a chip rated at 25 MHz, that means
>>that *that chip* (not just one of the same batch) has *already* failed at
>>least once at 33 MHz! Trusting it because "it seems to work OK for me..."
>>is *dumb*.
>
>  Which is a great assumption until the chip fab has tuned the process
>to a point that they are yeilding 40 Mhz parts all the time.  Then it
>becomes a marketing issue.
>
>  Say this month Motorola will sell the following breakdown of chips;
>
>       5000 40Mhz 68040's
>       10000 33Mhz 68040's
>       50000 25Mhz 68040's
>
>  The chip fab yeilds 100% good parts.  The process has been pretty good
>lately.  They know what breakdown they need, so they start testing and
>marking parts.  Once they've tested 5000 parts at 40 Mhz, they mark them
>and reload the tester with the 33 Mhz program.  They test 10000 more parts
>at 33 Mhz, mark them and reload the tester with the 25 Mhz program. etc.

In the real, competitive world of chip making, I doubt whether they would
really do this. When their manufacturing technology reaches the point where
the number failing at 33 MHz is sufficiently small, they don't sit on their
laurels -- they design a 50 MHz chip, split the resulting chips into 50,
40, and 33 MHz batches using the method I described, dump the surviving 25 MHz
chips at ridiculous prices, and life goes on.


--
...... Ross Smith (Wanganui, NZ) ...... [e-mail] ......
                  "Sir, trust me. My whole case hinges on
               proving you're a dork." (Kryten, "Red Dwarf")