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TP General - Mobile Flash-Cosmic Rays/Soft Fails mobile computers
Applicable to: World-Wide
Service Information:
The following are approved Questions & Answers from IBM Research on the subject. IBM will be publishing a sizeable research paper shortly on this emerging topic.
WHY IS THIS IMPORTANT?
Since we removed parity memory from our ThinkPads, some customers have been concerned over data integrity. THE GOOD NEWS - IBM Research has done the intial testing and WE DO NOT HAVE A PROBLEM! IBM Research is doing on-going testing as well.
We should be ready with Q's & A's should your customer inquire.
1. What are cosmic rays?
1a. Cosmic rays are nuclear particles from outer-space which constantly rain down onto earth. They mostly come from outside the solar system, originating from the birth of new stars. They are not infrequent - about two million pass through YOUR BODY every day! Cosmic rays were discovered by Hess in 1913, for which discovery he received the Nobel Prize.
2. What is a SOFT FAIL?
2a. The technical definition of a Soft Fail is the spontaneous non-reproducible change of information within a computer without any effect on the hardware. That means that there is no permanent damage to any part of the machine, only information stored in it has changed.
3. What causes Soft Fails?
3a. Soft fails are caused by electrical noise which reaches the computer memory circuits. Examples of sources of this noise might be static on the electrical power lines, radiation from lightning or local radiation from a sparking hair dryer. Cosmic rays do not cause soft fails directly, but interact with the materials of circuits to cause very small bursts of electrical charge which may upset the computer's circuits.
4. Are cosmic ray induced soft fails very common?
4a. A cosmic ray induced soft fail is not very common. A typical PC used 8 hours per day, might have one soft fail per year. However, there are various ways that such internal events disappear and never affect the user. A PC application may use only a small portion of the memory. If the soft fail occurs in a portion of memory which is written-over by an application, the soft fail disappears. And the most important reason that soft fails disappear is that whenever the PC is turned off, all of the memory is erased, including any soft fails.
5. Do soft fails affect mainframes where there are very big memories?
5a. Mainframes have very big memories, and the occurance of soft fails is more frequent than in PCs. However, the designers of mainframes are quite aware of the problem, and have spent great effort to be sure that whenever a soft fail occurs in memory, no matter what the source, it is detected and corrected. This adds to the expense of the computer system, but it is necessary to assure that any errors do not affect any of the user's programs. Every memory number is carefully checked before it is used to be sure that it is accurate and has not changed. This is done by a complicated program called "Error Checking and Correcting" which operates on every number used from the memory of a mainframe.
6. How were the effects of cosmic rays on computers discovered?
6a. The effects of any kind of radiation on electronics have tended to increase as the components of circuits have gotten smaller. It was not until the mid-1970's that circuits were small enough so that there could be any problem.
7. You have discussed soft fails as changing information in computer memories. Can cosmic rays affect logic also?
7a. Yes, any kind of electronic circuitry can be affected, but the possibility of affecting logic is much less than the effects on memory.
8. Do cosmic rays affect harddisk or floppy disk information?
8a. They are not affected by cosmic rays.
9. How do you protect computers from cosmic ray induced soft errors?
9a. Computer systems are protected from all kinds of possible errors by many complicated circuits. So if your systems is protected from noise, it is probably quite well protected from radiation induced errors.
10. Will Soft Errors interupt my computer? If it does, how long will it take to fix it? Will I loose my application which was running when the system crashed?
10a. Any error can interupt a computer system. It takes no longer to recover from a radiation induced soft fail, than from an interruption caused by a electrical storm.
11. Is it true that the probability of radiation induced soft errors can occur at higher altitudes?
11a. The increase in fail rate is only about 3X in Denver, which is the highest altitude city in North America. Also cosmic rays are attenuated by building materials, especially concrete. So if you are in an office building with several floors above you, the cosmic rays are greatly reduced.
12. I have a ThinkPad, and take many flights to Japan and Europe. Will I have any problems when I use my ThinkPad for business during these flights?
12a. Cosmic ray intensity increases with altitude, so the probability of a soft fail in a notebook computer is increased during airplane flights. A user would have to use a typical notebook computer continously on many long airline flights to have a significant chance of seeing one an error.
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General Information | |
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Date Created |
30-04-96 | |
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Last Updated |
26-01-99 | |
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Revision Date |
26-01-2000 | |
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IBM ThinkPad | |
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Product Family |
ThinkPad 300, ThinkPad 310, ThinkPad 315, ThinkPad 340, ThinkPad 345, ThinkPad 350, ThinkPad 355, ThinkPad 360, ThinkPad 365X/XD, ThinkPad 365C/CS, ThinkPad 365CD/CSD, ThinkPad 365E/ED, ThinkPad 370, ThinkPad 380, ThinkPad 380D, ThinkPad 380E, ThinkPad 380ED, ThinkPad 380XD, ThinkPad 380Z, ThinkPad 385D, ThinkPad 385E, ThinkPad 385ED, ThinkPad 385XD, ThinkPad 500, ThinkPad 510, ThinkPad 560, ThinkPad 560E, ThinkPad 560X, ThinkPad 560Z, ThinkPad 600, ThinkPad 600E, ThinkPad 700, ThinkPad 701, ThinkPad 710, ThinkPad 720, ThinkPad 730, ThinkPad 750, ThinkPad 755C/CS, ThinkPad 755CE/CSE, ThinkPad 755CX, ThinkPad 755CV, ThinkPad 755CD, ThinkPad 755CDV, ThinkPad 760C, ThinkPad 760E, ThinkPad 760CD, ThinkPad 760L/LD, ThinkPad 760ED, ThinkPad 760XD, ThinkPad 760EL/ELD, ThinkPad 760XL, ThinkPad 765L, ThinkPad 765D, ThinkPad 770, ThinkPad 770E/ED, ThinkPad 770X, ThinkPad 770Z | |
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Machine Type |
2615, 2600, 2610, 2620, 2618, 2619, 2625, 2624, 9545, 2635, 2636, 2603, 2604, 2640, 2641, 2645, 2646, 9552, 2630, 2523, 2524, 9546, 9547, 9548, 9549, 9544 | |
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