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Frodo Looijaard
b8ea339ede
git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@218 7894878c-1315-0410-8ee3-d5d059ff63e0
30 lines
1.5 KiB
Plaintext
30 lines
1.5 KiB
Plaintext
The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of
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functionality. Among other things, it implements the PCI bus. One of its
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minor functions is implementing a System Management Bus. This is a true
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SMBus - you can not access it on I2C levels. The good news is that it
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natively understands SMBus commands and you do not have to worry about
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timing problems. The bad news is that non-SMBus devices connected to it
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can confuse it mightily. Yes, this is known to happen...
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Cat /proc/pci, and see whether it contains an entry like this:
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Bus 0, device 1, function 3:
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Bridge: Intel 82371AB PIIX4 ACPI (rev 1).
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Medium devsel. Fast back-to-back capable.
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Bus and device numbers may differ, but the function number must be identical
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(like many PCI devices, the PIIX4 incorporates a number of different
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'functions', which can be considered as separate devices). If you find such
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an entry, you have a PIIX4 SMBus controller.
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On some computers (most notably, some Dells), the SMBus is disabled by
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default. If you compile the i2c-piix4 module with '-DFORCE_PIIX4_ENABLE',
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it will try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not
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set up a correct address for this module, you could get in big trouble
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(read: crashes, data corruption, etc.). Try this only as a last resort
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(try BIOS updates first, for example), and backup first!
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The PIIX4E is just an new version of the PIIX4; it is supported as well. The
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PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use this
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driver on those mainboards.
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