SDB:General Hardware Problems
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One or more of the following phenomena occur:
- Timing problems when accessing the CD-ROM (halt, long delays, bus errors, segmentation faults)
- Kernel generation (or compilation of other programs) aborts with signal 11
- Kernel generation (or compilation of other programs) aborts with signal 7
- Incorrect file contents
- Memory access errors
- Graphics are not displayed correctly
- crc errors when accessing the floppy disk drive
- Crashes or halts during boot
- Errors when creating a file system (mke2fs reports errors)
These strange phenomenona are most probably due to faulty or incorrectly configured hardware. The reason for this is that many motherboards apparently have timing problems. These timing problems become visible through bus errors (CPU-memory-PCI-ISA).
Even if the system is stable under DOS or Windows, for example, this does not matter in regards to the stability of the hardware and its configuration. The hardware manages to work with the slow segmented memory access of a CPU working in 16-bit realmode (under DOS, Windows). As soon as the memory is accessed in linear mode with 32-bit bursts, errors can occur. A further cause can be a badly cooled CPU or too slow or faulty (heat-sensitive) RAM modules.
The real cause is faulty hardware, not the operating system, like Linux. Linux requires more hardware stability than some other operating systems do. On the one hand, this provides increased performance. On the other hand, it can lead to the above-mentioned problems on some systems. In contrast to other operating systems, Linux assumes that the hardware works properly and is stable. If this is not the case, Linux stops working.
An operating system that still runs with faulty or potentially faulty hardware represents a severe security risk.
There are numerous parameters and conditions that can be changed to isolate the faulty equipment.
- Switch off the internal and external cache using the BIOS setup.
- Avoid overclocking of all kinds (CPU, system bus, graphics card)
- Reduce the bus clock (VLB maximum 40MHz, PCI bus according to the specification, maximum 66 MHz ext. processor clock): use BIOS setup or jumpers on the motherboard.
- Add waitstates: use BIOS setup
- Check if the BIOS option 15-16M Memory Hole is active. If so, deactivate this option.
Make sure the BIOS option PnP OS is set to 'No'. On some systems, this option might be called Installed OS and should be set to 'Other'. See SDB:Problems Caused by the BIOS Option "PnP OS"
- In (Advanced) Chipset Setup, if available, set
CAS before RAS: use BIOS setup
- Test the memory:
To check your RAM, use memtest86 or follow the instructions in SDB:Checking System Stability
- There will always be problems where modules of different kinds are used together.
- When using a PCI bus with 66 MHz, the DRAM modules must be specified with 60ns or less (no overtiming).
- Check the fittings of the RAM modules. They must fit exactly and must not be loose or tilt. Remove the modules from the board and put them back in (check for corroded contacts).
- Change the order of the modules in the memory banks.
- Check if the CPU fan works and whether it really fits exactly on the CPU (if necessary, use heat transfer paste).
- Switch off Power Management (APM). This was noticed several times as a source of errors, particularly in conjunction with the 2940: use the BIOS setup.
- Some Pentium clones cause problems if the kernel or the compiler were optimized for the Pentium, but a K6 or a Cyrix 6x86 is used instead. On such a system, optimize the kernel and the programs for a 486 at the maximum. If might even be necessary to fall back to 386 optimization.
- Check all general BIOS settings. If necessary, revert to the (rather conservative) BIOS defaults.
- If the PC BIOS is buggy, the only solution is a BIOS update. Ask your local dealer or the manufacturer of the motherboard.
- The power supply does not provide enough electricity or the voltage fluctuates: Try switching off some other appliances.
For More Information:
- The SIG11 problem: http://www.bitwizard.nl/sig11