On Thursday, November 15, 2018, 12:49:56 PM PST, juan <[email protected]>
wrote:
On Wed, 14 Nov 2018 21:15:29 +0000 (UTC)
jim bell <[email protected]> wrote:
me >> IIRC you also worked for intel designing memory chips? Excuse my
rather naive question but...Did you see/hear at that time any hints that chips
were being tampered with or somehow backdooored because of 'national
security'?
>> I didn't design memory chips. I was a "product engineer" for a specific
>> self-refreshing dynamic RAM
> I guess I didn't recall correctly then =P . I must have assumed that
product engineer more or less meant designer.
A "design engineer" is a person who designs the circuitry. A "process
engineer" is a person who specializes in the chemistry, photolithography, ion
implantation, etching, and other steps involved in the creation of a processed
silicon wafer. The whole process is amazingly complicated.
When I worked for Intel (1980-1982), a typical silicon linewidth was 3 microns.
(3000 nanometers.) Recently I saw that Intel was using a 10 nanometer
process, 300x smaller in linear size, and (300x)**2 (90,000) smaller in area.
What's truly amazing is how they have come to be able to etch such small
feature-sizes on silicon. For a long time, they were using 193 (?) nanometer
UV light to do that, and yet they got feature-sizes below 50 nanometers. (using
a lot of photolithographic 'tricks' to do so!.) Now, I think they probably use
"EUV", short for "Extreme Ultraviolet", which amounts to soft-xrays, maybe at
about 10nm wavelength or even shorter.
https://en.wikipedia.org/wiki/Extreme_ultraviolet
https://en.wikipedia.org/wiki/Extreme_ultraviolet_lithography>> In fact, I was
the first person at Intel, and perhaps in the world, who saw the flash(es)
through the microscope of the as-being-blown fuses on these chips. Intel was
doing this redundancy before anyone else, I believe.
> Interesting. I thought that sort of patching was something relatively new
only done to the chips in sdcards and the like. I guess it's not new. ×
No, it's definitely not new! Although, it was somewhat hush-hush at the time.
Apparently the big chip-buyers might not have liked to hear of these 'repair'
techniques. They probably had these pictures in their minds of perfect chips
emerging efficiently from the production line. But, they also wanted to buy
cheaper chips, and it was hard to make a truly-defect-free chip when you're
trying to put 65,536 transistors into the array of a DRAM. The
more-sophisticated users no doubt were told of this technique, and they
probably gave extra care to testing incoming parts.
Hard-disk manufacturers probably characterize their platters in a similar way,
looking for weak areas that have trouble recording data.
Jim Bell
