Q & A – PLL IC (Clock Generator)

This document provides some frequently asked questions about Sandra. Please read the Help File as well!

Q: Does Sandra support the clock generator of my mainboard?
The clock generator is supported only if the following are true:

  1. The mainboard is known, thus the PLL IC is known or PLL IC can be auto-detected.
  2. The mainboard SMBus/i2c controller is detected and enabled.
  3. The PLL IC is actually connected to the SMBus/i2c bus.
  4. The PLL IC supports read-back.
  5. The PLL IC is supported. See the Compatibility Document for the list of supported chips.

Q: PLL IC detection locks up my computer completly! Why and how do I fix it?
Your PLL IC is write-only. See Chipset Q & A for more information.

Q: Why doesn’t Sandra detect PLL ICs natively?
Only the very latest PLL IC chips can be autodetected. The older ones cannot – most cannot be detected at all!

Q: Sandra detects my PLL IC incorrectly!
Go to module Options and turn Auto Detect PLL IC off. If this does not help, contact us.

Q: Why does Sandra support so few clock generators?
The reasons are quite a few:

  • Only modern clock generators (since around 1997) are software programmable.
  • Most clock generators are write-only (e.g. the entire IC-Works line). This means that the bus speed can be changed but it cannot be detected. This is not a problem for programs like SoftFSB but it is critical for Sandra.

Q: Sandra does not detect the PLL IC of my mainboard!
PLL ICs (unlike other SMBus/i2c devices) cannot be detected. This is because there are no ID registers and most are write-only. One of the few possible ways is to do it by mainboard type. If Sandra does not know what your board uses, have a look and let us know.

Q: Sandra does detect the PLL IC type but cannot find it.
There are various reasons why this can happen:

  • Sandra does not detect the SMBus/i2c controller or the controller has locked.
  • The PLL IC is not at its known address or it is write-only.
  • The PLL IC has locked.

Q: Sandra does detect the PLL IC and reads it fine, but I get no useful information.
If the speed selected is by hardware then no useful information can be inferred. Only if the chip is software programmed useful information can be read back.

Q: How can I modify the FSB by software?
Sandra is an analyser not a PLL IC programmer. You can use programs like SoftFSB to program the PLL IC.


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