🚀 go-pugleaf

>In article <3115B199.1572@azstarnet.com>, bill_h <bill_h@azstarnet.com> wrote:
>>
>>In the US you can call 800-726-7827 and ask about memory test products
>>from a company called RAMSTAR. Seems to me their standard DRAM tester
>>cost about $250 several years ago. I have one.
>>
>>Even more important would be to request copies of their 'Tech Reports'
>>on memory and speed. And misc other topics.
>>
>>In general, YOU CAN NOT TRUST THE SPEED NUMBERS PRINTED ON THE CHIPS.
>>
>>A manufacturer would USUALLY only run ONE production line at a time,
>>and produce ONE basic chip geometry. If you called him up to order
>>300,000 chips, and wanted 70ns, and he was running a 60ns basic part,
>>you'd get your chips, marked 70ns, and costing a little less than the
>>60ns part, BUT IT WOULD BE THE EXACT SAME PART. 
>>It cost too much, and was inefficient to run different product
>>versions. Usually they'd upgrade all lines to the same mask-set
>>revision level as soon as they could.
>>
Excuse me for butting in, but I have watched Micron make chips.  I
have friends who work on the line out at Micron, not 5 miles from my
house.  You seem to have the idea that a 70ns chip and a 60ns chip ARE
SUPPOSED to be different.  The chips all start out on the same wafer,
with the same die.  Speed of the chip is mostly affected by impurities
and imperfections in the individual "chips" that make up a wafer.  The
wafers are sawed up, the individual pieces are tested, packaged and
tested again, for reliablility and speed, then marked with a speed
rating.  They are tested various ways, including in an oven.  Every
chip is tested for speed, and given a rating of the fastest speed at
which it can reliably operate.

While I just gave an overly simplified description of the process, the
main point is this:

Two chips that are identical except for the speed rating ARE
"identical," except that one chip operates reliably at a faster speed.

As the life cycle of a particular process technology progresses, the
yield of good chips goes up, and the percentage of faster chips on a
particular wafer goes up, too.  People who buy in lots of 300,000
chips do it by contract, with prices set in advance.  The vendor has
plenty of time to select the appropriate speed chips.  (Unless he is
having trouble meeting demand, in which case he might substitute chips
rated faster than the contract specifies.)  The buyer isn't going to
care.

With used chips, things can change depending on the conditions under
which the chips are used.

Just my 50 cents worth.

Matt Bell

BTW, I do not work at Micron, and never have.