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| Thinkpad W541 | |
|---|---|
| Manufacturer | Lenovo |
| Code name | W541 |
| Release date | |
| Device type | Laptop |
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Potential pitfalls
- The motherboard will not turn on without the I/O SubCard connected. Actually it will turn on and then immediately assert -PWRSHUTDOWN, which will cause the first mosfet (Q9) to immediately go off. This is most likely because the subcard has a power switch or regulator on it that is turned on by the VCC5MUBAY_DRV signal, and then the EC expects VCC5MUBAY to go high, and when it doesn't see it go high, it assumes something is wrong and turns off. Temporarily shorting TP28(VCC5M_IO_PWR-) to TP29(VCC5MUBAY) allows the motherboard to turn on even without the I/O SubCard.
- When flashing the BIOS using a SOIC clip, the programmer device needs to strongly drive the HOLD# pin high. A 5.6kOhm pull-up was not strong enough. A dead short worked successfully.
- The 4MiB and 8MiB BIOS flash chips share MISO/MOSI/SCK lines. When programming them using a SOIC clip, it has been observed that often the CS# line of the other chip has a low enough voltage and that the other chip could be considered selected as well. This did not cause a reading/programming failure so far, but if any issues are observed in the future, then it may be worth forcing the CS# line of the other chip high.