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 
>    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 
>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 
>processors support the so-called pseudo target 
>row refresh (pTRR) that can be used in 
>combination with pTRR-compliant DDR3 
>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 
>[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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