PC World 1999 August/PCWorld_1999-08_cd.bin/doc/FAQ/txt/GCC-SIG11-FAQ

Text File | 1999-04-09 | 37KB | 690 lines

                     Signal 11 while compiling the kernel

   This FAQ describes what the possible causes are for an effect that
   bothers lots of people lately. Namely that a linux(*)-kernel (or any
   other large package for that matter) compile crashes with a "signal
   11". The cause can be software or (most likely) hardware. Read on to
   find out more.
   (*) Of course nothing is Linux specific. If your hardware is flaky,
   Linux, Windows 3.1, FreeBSD, Windows NT and NextStep will all crash.
   If you are not reading this at http://www.bitwizard.nl/sig11/, that's
   where you can find the most recent version.
   For those of you who prefer reading this in French, the French
   translation can be found at
   http://www.linux-france.com/article/sig11fr/.
   Email me at [e-mail] if you find any spelling errors,
   worthwhile additions or with an "it also happened to me" story. (Note
   that I reject some suggested additions on my belief that it is
   technical nonsense).
     _________________________________________________________________

The Sig11 FAQ

  QUESTION

   My kernel compile crashes with
      gcc: Internal compiler error: program cc1 got fatal signal 11

   What is wrong with the compiler? Which version of the compiler do I
   need? Is there something wrong with the kernel?

  ANSWER

   Most likely there is nothing wrong with your installation, your
   compiler or kernel. It very likely has something to do with your
   hardware. There are a variety of subsystems that can be wrong, and
   there is a variety of ways to fix it. Read on, and you'll find out
   more. There is one big exception to this "rule". Red Hat 5.0. There is
   more near the end.
     _________________________________________________________________

  QUESTION

   Ok it may not be the software, How do I know for sure?

  ANSWER

   First lets make sure it is the hardware that is causing your trouble.
   When the "make" stops, simply type "make" again. If it compiles a few
   more files before stopping, it must be hardware that is causing you
   troubles. If it immediately stops again (i.e. scans a few directories
   with "nothing to be done for xxxx" before bombing at exactly the same
   place), try
        dd if=/dev/HARD_DISK of=/dev/null bs=1024k count=MEGS

   Change HARD_DISK to "hda" to the name of your harddisk (e.g. hda or
   sda. Or use "df ."). Change the MEGS to the number of megabytes of
   main memory that you have. This will cause the first several megabytes
   of your harddisk to be read from disk, forcing the C source files and
   the gcc binary to be reread from disk the next time you run it. Now
   type make again. If it still stops in the same place I'm starting to
   wonder if you're reading the right FAQ, as it is starting to look like
   a software problem after all.... Take a peek at the "what are the
   other possibilities" question..... If without this "dd" command the
   compiler keeps on stopping at the same place, but moves to another
   place after you use the "dd" you definitely have a disk->ram transfer
   problem.

  QUESTION

   What does it really mean?

  ANSWER

   Well, the compiler accessed memory outside its memory range. If this
   happens on working hardware it's a programming error inside the
   compiler. That's why it says "internal compiler error". However when
   the hardware occasionally flips a bit, gcc uses so many pointers, that
   it is likely to end up accessing something outside of its addressing
   range. (random addresses are mostly outside your addressing range, as
   not very many people have a significant part of 4G as main memory...
   :-) It seems that nowadays, everybody with "signal 11" problems gets
   directed to this page. If you're developping your own software or have
   software that hasn't been debugged quite enough, "signal 11" (or
   segmentation fault) is still a strong hint that there is something
   wrong with the program. Only when you can cause a "known working"
   program like "gcc" to crash on a dataset (e.g. the Linux-kernel) that
   has also been well-tested, then it becomes a hint that there is
   something wrong with your hardware.
     _________________________________________________________________

  QUESTION

   Ok. I may have a hardware problem what is it?

  ANSWER

   If it happens to be the hardware it can be:
     * Main memory. Your main memory might be getting an occasional bit
       wrong. If this happens on the "writes", you won't see any parity
       errors. There are several ways to fix it:
          + The memory speed might be too slow. Increase the number of
            wait states in the BIOS.
            This could be caused by the AMIBIOSs autoconfig option: it
            may only know about 486s running upto 80 MHz, whereas you
            currently buy 100 MHz versions. -- Pat V.
          + The memory speed might be too slow. Get faster DRAM SIMMs.
            For example current ASUS motherboards require 60 ns DRAM if
            you have a 100, or 133 MHz processor (Take a look in your
            motherboard's manual). I've heard reports that 70 ns also
            works, reliability problems like random sig11's belong to the
            possibilities.... (I wouldn't take the risk) -- Andrew
            Eskilsson ([e-mail])
          + There is a bad chip on one of the SIMMs. If you own more than
            1 bank of memory you might be able to pull SIMMs and see if
            the problem goes away. Be careful for STATIC!!!
          + We handled a hard one here the last week. It turned out that
            ALL 4 16Mb SIMMs were broken in that they dropped a bit
            around once per hour. This was sufficient to crash the
            machine in about a day, or crash a kernel compile in about an
            hour. A new set of SIMMs works perfectly. It took a long
            while to diagnose this one, because all 4 of the SIMMs were
            affected equally, so leaving half of the memory out didn't
            change things.
            Mark Kettner ([e-mail]) reports that his
            system was capable of running my memory test for 2300 times
            faultlessly, but then detected around 10 errors. It then
            continued detecting no faults for a few hundred runs
            again..... In his case running kernel compiles was a much
            more efficient way of detecting the health of the system (in
            the most stable configuration the system could compile around
            14 kernels before going bzurk). His solution was to "trade
            in" the old memory for a so called "memory upgrade". The
            shopkeeper then "tests" in their memory tester, which OKs the
            memory. he then got a good discount on the new memory :-).
          + It seems that some 30-72 pin converters can cause memory
            errors. (It hasn't been proven whether the 4 SIMMS in the
            converter had gone bad, or if the SIMM converter was at
            fault. The SIMMS had been functioning perfectly for years
            before they were moved into the converter....) -- Naresh
            Sharma ([e-mail]). Paul Gortmaker
            ([e-mail]) adds that the SIMM converters
            should have at least 4 bypass capacitors to keep the power
            supply of the SIMMs clean.
          + If the refresh of the DRAM isn't functioning properly, the
            DRAMs will slowly lose their information. Some (486)
            motherboards stop refreshing correctly when you turn on
            "hidden refresh". There seems to be a program called "dram"
            around that can also mess up your refresh to cause sig11
            problems. -- Hank Barta ([e-mail]), Ron Tapia
            ([e-mail])
          + The number of waitstates could be too low. Increase the
            number of waiststates in the BIOS for a fix. The Intel
            Endeavour board doesn't allow you to increase the memory
            waitstates. This can supposedly be fixed by flashing a MR
            BIOS into the motherboard. -- David Halls
            ([e-mail])
     * Cache memory. Your cache memory might be getting an occasional bit
       wrong. Caches are usually not equipped with parity. You can
       diagnose that this is the case by turning off the cache in the
       BIOS. If the problem goes away it is probably the cache. There are
       several ways to fix it:
          + The cache memory speed might be too slow. Increase the number
            of wait states in the BIOS.
          + The cache memory speed might be too slow. Get faster SRAM
            chips.
          + There is a bad chip in your cache. It is unlikely that you
            can swap chips as easily as with SIMMs. Be careful for
            STATIC!!! -- Joseph Barone ([e-mail])
          + The cache might be set to "write back" while there is a bug
            in the write back implementation of your chipset. The
            motherboard where this happened was a "MV020 486VL3H" (with
            20M RAM) -- Scott Brumbaugh ([e-mail])
            (Mail address doesn't work. Scott: Get back at me with a
            valid return address)
          + The motherboard may require a jumper to switch between Cache
            On A Stick and the old-fashioned dip chip cache. (JP16 on Rev
            2.4 ASUS P/I-P55TP4XE motherboards)
     * Disk transfers. A block coming from disk might incur an occasional
       bit error.
          + If you have this problem, you are most likely to have to do
            the "dd" command to "move" the problem from one place to the
            next....
          + Some IDE harddisks cannot handle the "irq_unmasking" option.
            This may only show under load. And it could show as a sig11.
          + Do you have a kalok 31xx? Throw it in the garbage. (or sell
            it to a DOS user)
          + SCSI? Termination? A short bus might still work (unreliably
            that is) with bad termination. A long bus might get errors
            anyway. Can you turn on parity on the host and the DISK?
     * Overclocking. Some vendors (or private people) think it is
       possible to overclock some CPUs. Some of them may work others
       don't. You might want to try turning off turbo (note that most
       pentium motherboards no longer support a non-turbo mode) and see
       if the problem goes away. Check the speed of your CPU compared
       (printed on it, carefully remove the fan if necessary) with what
       the motherboard jumpers or BIOS settings say.... It seems that
       even Intel may make mistakes in this area. I now have several
       reliable reports that official pentium would sig11 at their rated
       speed, but not at a lower speed. As for some speeds the
       motherboard is only stressed HARDER for a slower processor speed,
       (120 MHz-> motherboard runs at 60MHz, 100MHz-> motherboard runs at
       66MHz), I think it is unlikely that this has anything to do with
       the motherboard. Moreover a new 120MHz processor is now
       functioning correctly. -- Samuel Ramac ([e-mail]). This
       is not unique to Intel or any of its competitors.
     * CPU temperature. A high speed processor might overheat without the
       correct heat sink. This can also be caused by a failing fan. (My
       personal '486 has a fan that takes a few minutes to get up to
       speed. It probably will never really FAIL because it's now
       decommisioned :-). The CPU can become erratic if "pushed" by
       compiling a kernel. This problem becomes worse if you disable
       "HALT" on the LILO command line. Linux tries to power-down the CPU
       by executing the "halt" instruction when the system is idle. This
       preserves power, and therefore the CPU temperature drops when the
       system is idle. You therefore might not notice this problem when
       simply editing, and it might only surface after hours of CPU
       intensive jobs when the ambient temp is high. If you have a
       Pentium with Fdiv bug, it is advisable to trade it in at Intel.
       They will send you a new one that preconfigured with an official
       Intel-approved FAN. Also note that most normal glues are very bad
       thermal conductors. There is special thermal glue available that
       should be used when a fan needs to be glued to a CPU. -- Arno
       Griffioen ([e-mail]), -- W. Paul Mills ([e-mail]) --
       Alan Wind ([e-mail])
       Intel says that the allowable temperature ranges for the outside
       of your CPU is:
       0 to +85 C: Intel486 SX, Intel486 DX, IntelDX2, IntelDX4 processor
       0 to +95 C: IntelDX2, IntelDX4 OverDrive« processors
       0 to +80 C: 60 MHz Pentium« processor
       0 to +70 C: 66 to 166 MHz Pentium processor
       For information on how to measure this and some confirmation of
       what I say here, see:
       http://pentium.intel.com/procs/support/faqs/iarcfaq.htm
       (Especially questions Q5, Q6 and Q12. The document is getting
       slightly outdated, but it is still very accurate. It seems the
       questions move around a bit every now and then as well.)
     * CPU voltage. Some motherboards allow you to select the CPU
       voltage. Some motherboards badly document the jumper settings that
       manage this. It seems that a 5V processor might still work most of
       the time at 3.3 volts..... -- Karl Heyes ([e-mail])
     * RAM voltage. It seems that vendors are preparing for 3.3V RAM now.
       Most memory is still 5V. (but be careful.... 3.3v RAM will break
       at 5V.....)
     * Local bus overloading. At 25 MHz you're allowed to have 3
       VesaLocalBus (VLB) cards, At 33MHz only two, at 40MHz only one and
       guess what at 50MHz NONE! (i.e. you are allowed to run your system
       with a 50MHz local bus, but then you're not allowed to use any VLB
       cards). Some systems start acting flaky when you overload the VLB.
       Even when your VLB isn't overloaded (over the limits stated
       above), the system may lose a few nanoseconds of margin by adding
       an extra VLB card, so you might need to add a cache wait state or
       something after you've added a new VLB card.... -- Richard
       Postgate ([e-mail])
     * Power management. Some laptops (and nowadays also "green" pc's)
       have power management features. These might interfere with Linux.
       One feature might save a memory image to HD and restore the RAM
       when you press a key. This sounds like fun, but Linux device
       drivers don't expect that the hardware has been turned off between
       two acesses. Some may recover, but others not. Try turning it off,
       or enabeling "APM support" in your kernel. -- Elizabeth Ayer
       ([e-mail])
     * The CPU itself. Several people are reporting that they have found
       nothing to blame except the CPU. This could also have been an
       incompatibility between the CPU and the motherboard. A wave of
       reports concerning Intel CPUs has passed (Feb '97). A new wave of
       reports is coming in that are blaming Cyrix/IBM 6x86 CPUs.
       Although it could indeed be the CPU, it could also be that your
       motherboard is incompatible with your CPU. At least I've seen a
       motherboard manual mention that it isn't compatible with older
       6x86's. My own experience is that these devices aren't bad at all,
       and on a kernel compile I benchmarked a P166+ to be equivalent
       with a P155 (1.3 times faster than a P120).

     The Memory hole. Many modern motherboards allow you to use old ISA
   video cards with one or two megabytes of linear frame buffer. To
   achieve this, they have to map out the memory just below 16Mb. Nobody
   actually ever used this feature, but if you turn the memory hole (or
   LFB support in some BIOSes) on, your machine will certainly be
   flaky..... -- Paul Connolly ([e-mail])
     _________________________________________________________________

  QUESTION

   RAM timing problems? I fiddled with the bios settings more than a
   month ago. I've compiled numerous kernels in the mean time and nothing
   went wrong. It can't be the RAM timing. Right?

  ANSWER

   Wrong. Do you think that the RAM manufacturers have a machine that
   makes 60ns RAMs and another one that makes 70ns RAMs? Off course not!
   They make a bunch, and then test them. Some meet the specs for 60 ns,
   others don't. Those might be 61 ns if the manufacturer would have to
   put a number to it. In that case it is quite likely that it works in
   your computer when for example the temperature is below 40 degrees
   centigrade (chips become slower when the temp rises. That's why some
   supercomputers need so much cooling).

   However "the coming of summer" or a long compile job may push the
   temperature inside your computer over the "limit". -- Philippe Troin
   ([e-mail])
     _________________________________________________________________

  QUESTION

   I got suckered into not buying ECC memory because it was slightly
   cheaper. I feel like a fool. I should have bought the more expensive
   ECC memory. Right?

  ANSWER

   Buying the more expensive ECC memory and motherboards protects you
   against a certain type of errors: Those that occur randomly by passing
   alpha particles.
   Because most people can reproduce "signal 11" problems within half an
   hour using "gcc" but cannot reproduce them by memory testing for hours
   in a row, that proves to me that it is not simply a random alpha
   particle flipping a bit. That would get noticed by the memory test
   too. This means that something else is going on. I have the impression
   that most sig11 problems are caused by timing errors on the CPU <->
   cache <-> memory path. ECC on your main memory doesn't help you in
   that case. When should you buy ECC? a) When you feel you need it. b)
   When you have LOTS of RAM. (Why not a cut-off number? Because the
   cut-off changes with time, just like "LOTS".) Some people feel very
   strong about everybody using ECC memory. I refer them to reason "a)".
     _________________________________________________________________

  QUESTION

   Memory problems? My BIOS tests my memory and tells me its ok. I have
   this fancy DOS program that tells me my memory is OK. Can't be memory
   right?

  ANSWER

   Wrong. The memory test in the BIOS is utterly useless. It may even
   occasionally OK more memory than really is available, let alone test
   whether it is good or not.
   A friend of mine used to have a 640k PC (yeah, this was a long time
   ago) which had a single 64kbit chip instead of a 256kbit chip in the
   second 256k bank. This means that he effectively had 320k working
   memory. Sometimes the BIOS would test 384k as "OK". Anyway, only
   certain applications would fail. It was very hard to diagnose the
   actual problem....
   Most memory problems only occur under special circumstances. Those
   circumstances are hardly ever known. gcc Seems to exercise them. Some
   memory tests, especially BIOS memory tests, don't. I'm no longer
   working on creating a floppy with a linux kernel and a good memory
   tester on it. Forget about bugging me about it......
   The reason is that a memory test causes the CPU to execute just a few
   instructions, and the memory access patterns tend to be very regular.
   Under these circumstances only a very small subset of the memories
   breaks down. If you're studying Electrical Engineering and are
   interested in memory testing, a masters thesis could be to figure out
   what's going on. There are computer manufacturers that would want to
   sponsor such a project with some hardware that clients claim to be
   unreliable, but doesn't fail the production tests......
     _________________________________________________________________

  QUESTION

   Does it only happen when I compile a kernel?

  ANSWER

   Nope. There is no way your hardware can know that you are compiling a
   kernel. It just so happens that a kernel compile is very tough on your
   hardware, so it just happens a lot when you are compiling a kernel.
     * People have seen "random" crashes for example while installing
       using the slackware installation script.... -- [e-mail]
     * Others get "general protection errors" from the kernel (with the
       crashdump). These are usually in /var/adm/messages. --
       [e-mail]
     _________________________________________________________________

  QUESTION

   Nothing crashes on NT, Windows 95, OS/2 or DOS. It must be something
   Linux specific.

  ANSWER

   First of all, Linux stresses your hardware more than all of the above.
   Some OSes like the Microsoft ones named above crash in unpredictable
   ways anyway. Nobody is going to call Microsoft and say "hey, my
   windows box crashed today". If you do anyway, they will tell you that
   you, the user, made an error (see the interview with Bill Gates in a
   German magazine....) and that since it works now, you should shut up.
   Those OSes are also somewhat more "predictable" than Linux. This means
   that Excel might always be loaded in the exact same memory area.
   Therefore when the bit-error occurs, it is always excel that gets it.
   Excel will crash. Or excel will crash another application. Anyway, it
   will seem to be a single application that fails, and not related to
   memory.
   What I am sure of is that a cleanly installed Linux system should be
   able to compile the kernel without any errors. Certainly no sig-11
   ones. (** Exception: Red Hat 5.0 with a Cyrix processor. See
   elsewhere. **)
   Really Linux and gcc stress your hardware more than other OSes. If you
   need a non-linux thingy that stresses your hardware to the point of
   crashing, you can try winstone. -- Jonathan Bright
   ([e-mail])
     _________________________________________________________________

  QUESTION

   Is it always signal 11?

  ANSWER

   Nope. Other signals like four, six and seven also occur occasionally.
   Signal 11 is most common though.

   As long as memory is getting corrupted, anything can happen. I'd
   expect bad binaries to occur much more often than they really do.
   Anyway, it seems that the odds are heavily biased towards gcc getting
   a signal 11. Also seen:
     * free_one_pmd: bad directory entry 00000008
     * EXT2-fs warning (device 08:14): ext_2_free_blocks bit already
       cleared for block 127916
     * Internal error: bad swap device
     * Trying to free nonexistent swap-page
     * kfree of non-kmalloced memory ...
     * scsi0: REQ before WAIT DISCONNECT IID
     * Unable to handle kernel NULL pointer dereference at virtual
       address c0000004
     * put_page: page already exists 00000046
       invalid operand: 0000
     * Whee.. inode changed from under us. Tell Linus
     * crc error -- System halted (During the uncompress of the Linux
       kernel)
     * Segmentation fault
     * "unable to resolve symbol"
     * make [1]: *** [sub_dirs] Error 139
       make: *** [linuxsubdirs] Error 1
     * The X Window system can terminate with a "caught signal xx"

   The first few ones are cases where the kernel "suspects" a
   kernel-programming-error that is actually caused by the bad memory.
   The last few point to application programs that end up with the
   trouble.

   -- S.G.de Marinis ([e-mail])
   -- Dirk Nachtmann ([e-mail])
     _________________________________________________________________

  QUESTION

   What do I do?

  ANSWER

   Here are some things to try when you want to find out what is wrong...
   note: Some of these will significantly slow your computer down. These
   things are intended to get your computer to function properly and
   allow you to narrow down what's wrong with it. With this information
   you can for example try to get the faulty component replaced by your
   vendor.
     * Jumper the motherboard for lower CPU and bus speed.
     * Go into the BIOS and tell it "Load BIOS defaults". Make sure you
       write the disk drive settings down beforehand.
     * Disable the cache (BIOS) (or pull it out if it's on a "stick").
     * boot kernel with "linux mem=4M" (disables memory above 4Mb).
     * Try taking out half the memory. Try both halves in turn.
     * Fiddle with settings of the refresh (BIOS)
     * Try borrowing memory from someone else. Preferably this should be
       memory that runs Linux flawlessly in the other machine...
       (Sillicon graphics Indy machines are also nice targets to borrow
       memory from)
     * If you want to verify if a solution really works try the
       following:
    tcsh
    cd /usr/src/linux
    make zImage
    foreach i (0 1 2 3 4 5 6 7 8 9)
      foreach j (0 1 2 3 4 5 6 7 8 9)
        make clean;make zImage > log."$i"$j
      end
    end
       All the resulting logfiles should be the same. (The first "make
       zImage" makes sure that the dependencies are already
       generated.....) This takes around 24 hours on a 100MHz pentium
       with 16Mb of memory. (and about 3 months on a 386 with 4Mb :-).

   The hardest part is that most people will be able to do all of the
   above except borrowing memory from someone else, and it doesn't make a
   difference. This makes it likely that it really is the RAM. Currently
   RAM is the most pricy part of a PC, so you rather not have this
   conclusion, but I'm sorry, I get lots of reactions that in the end
   turn out to be the RAM. However don't despair just yet: your RAM may
   not be completely wasted: you can always try to trade it in for
   different or more RAM.
     _________________________________________________________________

  QUESTION

   I had my RAMs tested in a RAM-tester device, and they are OK. Can't be
   the RAM right?

  ANSWER

   Wrong. It seems that the errors that are currently occuring in RAMS
   are not detectable by RAM-testers. It might be that your motherboard
   is accessing the RAMs in dubious ways or otherwise messing up the RAM
   while it is in YOUR computer. The advantage is that you can sell your
   RAM to someone who still has confidence in his RAM-tester......
     _________________________________________________________________

  QUESTION

   What are other possibilities?

  ANSWER

   Others have noted the following possibilities:
     * Red Hat 5.0 crashes for some people while installing. Others are
       only running into problems when compiling the kernel. It seems
       that the gcc that comes with Red Hat 5.0 is odd in the respect
       that it crashes on Cyrix processors when compiling the kernel.
       This is VERY odd. I would think that the only way that this can be
       the case is whent he Cyrix has a bug that has gone undetected all
       this time, and reliably gets triggered when THAT gcc compiles the
       Linux kernel. Anyway, if you just want compile a kernel, you
       should get
       ftp://ftp.redhat.com/home/wanger/gcc/gcc-2.7.2.3-9.i386.rpm . (I
       had to change the URL twice in a week. If it changes again, you'll
       just have to click your way to the errata at starting at
       http://www.redhat.com/) I don't know of a workaround if your
       system crashes while installing, except for installing a minimal
       base and then adding packages using 'glint' or 'rpm'.
     * Compiling a 2.0.x kernel with a 2.8.x gcc or any egcs doesn't
       work. There are a few bugs in the kernel that don't show up
       because gcc 2.7.x does a lowsy job optimizing it. gcc 2.8.x and
       egcs just dump some of the code because we didn't tell it not to.
       Anyway, you usually get a kernel that seems to work but has funny
       bugs. For example X may crash with a signal 11. Oh, and before you
       ask, no it's not going to be fixed. Don't bother Alan or Linus
       about this OK? -- Hans Peter Verne ([e-mail])
     * The pentium-optimizing-gcc (the one with the version number ending
       in "p") fails with the default options on certain source files
       like floppy.c in the kernel. The "triggers" are in the kernel,
       libc and in gcc itself. This is easily diagnosed as "not a
       hardware problem" because it always happens in the same place. You
       can either disable some optimizations (try -fno-unroll-loops
       first) or use another gcc. -- Evan Cheng ([e-mail])
       (In other words: gcc 2.7.2p crashes with sig11 on floppy.c .
       Workaround-1: Use plain gcc. Workaround-2: Manually compile
       floppy.c with "-O" instead of "-O2". )
     * A badly misconfigured gcc -- some parts from one version, some
       from another. After a few weeks I ended up re-installing from
       scratch to get everything right. -- Richard H. Derr III
       ([e-mail]).
     * Gcc or the resulting application may terminate with sig11 when a
       program is linked against the SCO libraries (which come with
       iBCS). This occurs on some applications that have -L/lib in their
       LDFLAGS....
     * When compiling a kernel with an ELF compiler, but configured for
       a.out (or the other way around, I forgot) you will get a signal 11
       on the first call to "ld". This is easily identified as a software
       problem, as it always occurs on the FIRST call to "ld" during the
       build. -- REW
     * An Ethernet card together with a badly configured PCI BIOS. If
       your (ISA) Ethernet card has an aperture on the ISA bus, you might
       need to configure it somewhere in the BIOS setup screens.
       Otherwise the hardware would look on the PCI bus for the shared
       memory area. As the ISA card can't react to the requests on the
       PCI bus, you are reading empty "air". This can result in
       segmentation faults and kernel crashes. -- REW
     * Corrupted swap partition. Tony Nugent ([e-mail])
       reports he used to have this problem and solved it by an mkswap on
       his swap partition. (Don't forget to type "sync" before doing
       anything else after an mkswap. -- Louis J. LaBash Jr.
       ([e-mail]))
     * NE2000 card. Some cheap Ne2000 cards might mess up the system. --
       Danny ter Haar ([e-mail]) I personally might have had
       similar problems, as my mail server crashed hard every now and
       then (once a day). It now seems that 1.2.13 and lots of the 1.3.x
       kernels have this bug. I haven't seen it in 1.3.48. Probably got
       fixed somewhere in the meantime.... -- REW
     * Power supply? No I don't think so. A modern heavy system with two
       or three harddisk, both SCSI and IDE will not exceed 120 Watts or
       so. If you have loads of old harddisks and old expansion cards the
       power requirements will be higher, but still it is very hard to
       reach the limits of the power supply. Of course some people manage
       to find loads of old full-size harddisks and install them into
       their big-tower. You can indeed overload a powersupply that way.
       -- Greg Nicholson ([e-mail]) A faulty power supply CAN
       of course deliver marginal power, which causes all of the
       malfunctioning that you read about in this file.... -- Thorsten
       Kuehnemann ([e-mail])
     * An inconsistent ext2fs. Some circumstances can cause the kernel
       code of the ext2 file system to result in Signal 11 for Gcc. --
       Morten Welinder ([e-mail])
     * CMOS battery. Even if you set the BIOS as you want it, it could be
       changing back to "bad" settings under your nose if the CMOS
       battery is bad. -- Heonmin Lim ([e-mail])
     * No or too little swap space. Gcc doesn't gracefully handle the
       "out of memory" condition. -- Paul Brannan ([e-mail])
     * Incompatible libraries. When you have a symlink from "libc.so.5"
       pointing to "libc.so.6", some applications will bomb with sig11.
       -- Piete Brooks ([e-mail]).
     _________________________________________________________________

  QUESTION

   I don't believe this. To whom has this happened?

  ANSWER

   Well for one it happened to me personally. But you don't have to
   believe me. It also happened to:
     * Johnny Stephens ([e-mail])
     * Dejan Ilic ([e-mail])
     * Rick Tessner ([e-mail])
     * David Fox ([e-mail])
     * Darren White ([e-mail]) (L2 cache)
     * Patrick J. Volkerding ([e-mail])
     * Jeff Coy Jr. ([e-mail]) (Temp problems)
     * Michael Blandford ([e-mail]) (Temp problems: CPU fan
       failed)
     * Alex Butcher ([e-mail]) (Memory waitstates)
     * Richard Postgate ([e-mail]) (VLB loading)
     * Bert Meijs ([e-mail]) (bad SIMMs)
     * J. Van Stonecypher ([e-mail])
     * Mark Kettner ([e-mail]) (bad SIMMs)
     * Naresh Sharma ([e-mail]) (30->72 converter)
     * Rick Lim ([e-mail]) (Bad cache)
     * Scott Brumbaugh ([e-mail])
     * Paul Gortmaker ([e-mail])
     * Mike Tayter ([e-mail]) (Something with the
       cache)
     * Benni ??? ([e-mail]) (VLB Overloading)
     * Oliver Schoett ([e-mail]) (Cache jumper)
     * Morten Welinder ([e-mail])
     * Warwick Harvey ([e-mail]) (bit error in cache)
     * Hank Barta ([e-mail])
     * Jeffrey J. Radice ([e-mail]) (Ram voltage)
     * Samuel Ramac ([e-mail]) (CPU tops out)
     * Andrew Eskilsson ([e-mail]) (DRAM speed)
     * W. Paul Mills ([e-mail]) (CPU fan disconnected from CPU)
     * Joseph Barone ([e-mail]) (Bad cache)
     * Philippe Troin ([e-mail]) (delayed RAM timing
       trouble)
     * Koen D'Hondt ([e-mail]) (more kernel error
       messages)
     * Bill Faust ([e-mail]) (cache problem)
     * Tim Middlekoop ([e-mail]) (CPU temp: fan
       installed)
     * Andrew R. Cook ([e-mail]) (bad cache)
     * Allan Wind ([e-mail]) (P66 overheating)
     * Michael Tuschik ([e-mail]) (gcc2.7.2p victim)
     * R.C.H. Li ([e-mail]) (Overclocking: ok for months...)
     * Florin ([e-mail]) (Overclocked CPU by vendor)
     * Dale J March ([e-mail]) (CPU overheating on laptop)
     * Markus Schulte ([e-mail]) (Bad RAM)
     * Mark Davis ([e-mail]) (Bad P120?)
     * Josep Lladonosa i Capell ([e-mail]) (PCI options
       overoptimization)
     * Emilio Federici ([e-mail]) (P120 overheating)
     * Conor McCarthy ([e-mail]) (Bad SIMM)
     * Matthias Petofalvi ([e-mail]) ("Simmverter" problem)
     * Jonathan Christopher Mckinney ([e-mail]) (gcc2.7.2p victim)
     * Greg Nicholson ([e-mail]) (many old disks)
     * Ismo Peltonen ([e-mail]) (irq_unmasking)
     * Daniel Pancamo ([e-mail]) (70ns instead of 60 ns RAM)
     * David Halls ([e-mail])
     * Mark Zusman ([e-mail]) (Bad motherboard)
     * Elizabeth Ayer ([e-mail]) (Power management features)
     * Thorsten Kuehnemann ([e-mail])
     *
     * (Email me with your story, you might get to be mentioned here...
       :-) ---- Update: I like to hear what happened to you. This will
       allow me to guess what happens most, and keep this file as
       accurate as possible. However I now have around 500 different
       Email addresses of people who've had sig-11 problems. I don't
       think that it is useful to keep on adding "random" people's names
       on this list. What do YOU think?
     _________________________________________________________________

   I'm interested in new stories. If you have a problem and are unsure
   about what it is, it may help to Email me at [e-mail] .
   My curiosity will usually drive me to answering your questions until
   you find what the problem is..... (on the other hand, I do get pissed
   when your problem is clearly described above :-)
     _________________________________________________________________

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     _________________________________________________________________