Tim May's Passing Confirmed
John Young
jya at pipeline.com
Mon Dec 17 03:54:55 PST 2018
Another excellent, informative post. Thanks
twice, Jim, a swell way to honor Tim and others
who have made substantial gifts here and
elsewhere, now diminished by dreck-diseased SM
and corrupted by thieving ads, rants, trollings, biases, bots, Trumps. John
At 08:29 PM 12/16/2018, jim bell wrote:
>Maybe I should risk adding something about soft
>errors, which has some current relevance.
>Another way that the problem with
>alpha-particle-induced soft errors was by
>changing the semiconductor process for DRAMs
>from NMOS to CMOS. See the diagram for an NMOS
>DRAM
>cell.
><https://en.wikipedia.org/wiki/Dynamic_random-access_memory>https://en.wikipedia.org/wiki/Dynamic_random-access_memory
>
>
>
> An inherent part of the CMOS process is
> having a layer of opposite polarity just below
> the active components. When an alpha particle
> strikes the substrate of an NMOS chip, the
> resulting cloud of electrons get swept into the
> bit-cells. In a CMOS DRAM, the cloud of
> electrons is driven away from the bit cells,
> generally immunizing them against such
> upsets. So, my understanding is that
> alpha-induced soft-errors are generally no longer a threat.
>
>The current relevance is that: While there
>hasn't been a reference to it recently on the
>Cypherpunks list, there is a technique called
>"row-hammer",
><https://en.wikipedia.org/wiki/Row_hammer>https://en.wikipedia.org/wiki/Row_hammer
>which intends to take advantage of a slight
>weakness in some DRAMs such that repeatedly
>accessing rows physically near a desired row
>might cause bits in that nearby row to 'flip',
>or change state. While I don't claim to
>understand the details in the software, if this
>'works' software running in a microcomputer can
>spy on what other software processes are doing,
>when there should be no such ability.
>
>
>This is a tricky weakness. Ideally, you should
>be able to buy DRAMs which are entirely
>protected against 'row-hammer', but it's not
>easily known what designs (manufacturer's
>products) are weak. One possible protection, I
>think, is if computers have parity-bits
>available, and automatically checked, when DRAM
>computer memories are accessed. Parity DRAM
>memory used to be common, decades ago, but not
>so much anymore. This, I think, is a major mistake.
>
>See the Row Hammer article, under the section "Mitigation".
>
>"Since the release of
><https://en.wikipedia.org/wiki/Ivy_Bridge_(microarchitecture)>Ivy
>Bridge
><https://en.wikipedia.org/wiki/Microarchitecture>microarchitecture,
><https://en.wikipedia.org/wiki/Intel>Intel
><https://en.wikipedia.org/wiki/Xeon>Xeon
>processors support the so-called pseudo target
>row refresh (pTRR) that can be used in
>combination with pTRR-compliant DDR3
><https://en.wikipedia.org/wiki/Dual_in-line_memory_module>dual
>in-line memory modules (DIMMs) to mitigate the
>row hammer effect by automatically refreshing
>possible victim rows, with no negative impact on
>performance or power consumption. When used with
>DIMMs that are not pTRR-compliant, these Xeon
>processors by default fall back on performing
>DRAM refreshes at twice the usual frequency,
>which results in slightly higher memory access
>latency and may reduce the memory bandwidth by
>up to
>24%.<https://en.wikipedia.org/wiki/Row_hammer#cite_note-intel-d2s2e4-9>[9]"
>[end of partial quote]
>
>
> Jim Bell
>
>
>
>
>On Saturday, December 15, 2018, 1:19:08 PM PST,
>John Young <jya at pipeline.com> wrote:
>
>
>Excllent post, Jim, thanks.
>
>At 02:47 PM 12/15/2018, you wrote:
> >Tim May was very well-known in the 1979-era for his discovery that
> >alpha particles (helium nuclei) caused data-read errors in
> >then-current technology DRAMs.
> >
> >(An article from the last year or two incorrectly stated that we
> >met; I think that was simply a misinterpretation of the fact that I
> >also worked for Intel during 1980-82. But, I worked in Oregon,
> >Aloha-3 specifically; I believe May worked in Santa Clara. I never
> >visited any Intel locations outside Oregon; I do not recall that Tim
> >May ever visited Oregon.)
> >
> >One of the very minor things I did while working at Intel involved
> >Kapton (polyimide) 'shims' that were being experimented with to
> >protect against such errors caused by alpha particles. A
> >rectangular sheet of very thin plastic was attached over the DRAM
> >chip. Due to the very-low penetration characteristic of alphas,
> >this was plenty to stop them from striking the surface of the
> >chip. As part of the development and evaluation process, it was
> >occasionally necessary to remove those shims from assembled devices.
> >Peeling them off frequently destroyed the chip: I used a tiny part
> >of my Chemistry knowledge to recommend the use of the solvent, DMF
> >(dimethyl formamide) to assist in this removal process, in a way
> >which did not risk damage to the chip itself.
> >
> >The reason Intel had the problem of alpha particles was its heavy
> >use of "cerdip" packages.
> ><<http://eesemi.com/cerdip.htm>http://eesemi.co
> m/cerdip.htm>http://eesemi.com/cerdip.htm (short
> >for "ceramic dual inline package") Cerdip looks vaguely like an
> >Oreo cookie, with two ceramic plates attached with a glass
> >'glue'. That ceramic had tiny amounts of radioactive elements in
> >it; not a lot, but it didn't take much to produce a significant
> >amount of alphas. Cerdip was used because it achieved a hermetic
> >seal, but it was cheaper than a different kind of ceramic
> >packaging.
> ><<http://www.globalchipmaterials.com/visitors/p
> roducts_visitors.htm>http://www.globalchipmaterials.com/visitors/products_visitors.htm>http://www.globalchipmaterials.com/visitors/products_visitors.htm
>
> >
> >
> >Had they packaged their DRAMs in plastic, that would have been a
> >vast improvement, actually virtually eliminating the
> >problem: Production of plastics go through chemical processes where
> >their components (monomers) are distilled, and so they contain
> >virtually no radioactive atoms. But they couldn't immediately shift
> >to using plastic packaging, because such packages were not
> >hermetically sealed: Packaged in plastic, water from the
> >environment eventually found its way to the chip itself. The
> >problem with that is that this water slowly reacted with one
> >component of the glass, phosphorus-containing 'pyroglass'. (a
> >related material was 'pyrox') These phosphorus glasses slowly
> >reacted with that moisture to generate phosphoric acid, and in turn
> >that slowly corroded the very thin aluminum conductors making up
> >interconnects in that chip.
> >
> >Fixing the problem caused by alpha particles eventually required
> >changing the chip process so that it didn't require hermetic
> >packaging, making plastic packaging workable.
> >
> > Jim Bell
> >
> >
> >
> >
> >
> >On Saturday, December 15, 2018, 10:44:21 AM PST, John Young
> ><<mailto:jya at pipeline.com>jya at pipeline.com> wrote:
> >
> >
> >This confirms Tim May's passing, by long-time cpunk, Lucky Green
> >
> >Dear Friends, It is with sadness that news reaches me of the passing
> >of my dear friend Tim May - Cypherpunks co-Founder, Discoverer of
> >Radiation-Induced Single Even Upsets in Integrated Circuits, and
> >Uncompromising Firearms Proponent: Tweet:
> ><<https://twitter.com/luckygreen/status/1073925
> 779304693760>https://twitter.com/luckygreen/status/1073925779304693760>https://twitter.com/luckygreen/status/1073925779304693760
>
> >Obit:
> ><<https://www.facebook.com/lucky.green.73/posts
> /10155498914786706>https://www.facebook.com/lucky.green.73/posts/10155498914786706>https://www.facebook.com/lucky.green.73/posts/10155498914786706
>
> >Ad
> >Astra, Tim! --Lucky
> >
>
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