Embedded Controller Chips
Contents
| This page is a stub |
|---|
|
You can help ThinkWiki by expanding it. |
The ThinkPad Embedded Controller
This page contains information about Embedded Controller chips found in ThinkPads.
- Apparently used on all ThinkPads since the A30, T23, R40, X20.
- Unknown chips without field-upgradeable firmware
- Used on older ThinkPads, including the model 570, and maybe even earlier models.
Firmware issues
Various bugs have been observed in the various ThinkPad EC firmwares. Most of them were fixed in later revisions, but a few are either very dangerous and driver writers need to always work around them, or have never been fixed. One must keep in mind that many of the bugs fixed by IBM or Lenovo could cause serious problems, but might never be noticed by driver developers, because they usually keep their ThinkPads up-to-date. People that don't keep their ThinkPad firmware up-to-date are excellent guinea pigs...
Bug: Advanced battery query causes EC hang
- Severity: critical
- Fix: available from IBM, but not for all affected models
- Information: thread in linux-thinkpad ML
- Models affected:
- T40, T40p, T41, T41p, T42, T42p: all models affected, no fix available
- T43 26xx, T43p: fixed on firmware 1YHT28WW (1.05) and newer
- T43 18xx, R52: likely buggy, unknown status (might be fixed in latest firmwares)
- other ThinkPads featuring advanced battery queries: unknown status; every model supported by tp_smapi advanced battery information is a candidate for this bug
The EC LPC3B advanced battery query function 0x0B (only used by tp_smapi) has a hideous bug that causes the EC to misbehave and crash (usually hanging the entire ThinkPad). This function must never be called on a buggy firmware.
Bug: Fan control loop status is not initialized
- Severity: low
- Fix: unknown status at this time
- Information: thinkpads.com fan control programs forum, linux-thinkpad ML thread
- Models affected:
The EC does not correctly initializes its 0x2f (fan control) register, so ibm-acpi cannot determine the correct status of the fan control until something writes to the fan control register for the first time.
Bug: Fan control loop pulses the fan in an annoying pattern
- Severity: low
- Fix: available from IBM, but incorrectly fixed on some models. Unofficial fix available for firmware hackers.
- Workaround: A software workaround is available using an ACPI fan control script, but this overrides the embedded controller's fan control algorithm.
- Information: thinkpads.com forum thread, thinkpads.com forum thread, Problem with fan noise
- Models affected:
The fan control loop will vary the fan speed quite a lot, in a very annoying pattern. The broken fix on the T43 firmware causes annoying pulses every 30s.
Bug: Tachometer registers not invalidated in disengaged mode
- Severity: low
- Fix: none available
- Models affected:
- Nearly all ThinkPad models
When the fan control loop is placed in disengaged mode (bit 6 of EC register 0x2f is set) where no tachometer readings take place, the EC does not set the tachometer registers (0x84, 0x85) to 0xFF to signal an invalid reading. Instead, the registers are simply not updated anymore and retain the last tachometer reading that took place.
