Dear all,
I’m using ML605 board and downloading PCIe demo ( Gen2, x4 ) .
It’s attached to windows XP 32bit PC at Slot x16 PCI Express . When I check the Configuration Space
the negotiated speed is only x1 but not x4 .
Do you know the reason ?
I asked PCISIG forum and they ask to check the mother board if
it can support x4 . But I don’t know how to check .
Beside, it’s ask to check if x4 is done but it changes to x1 for
saving power . But I don’t have Bus capture for PCIe . I don’t know how to check also.
Please, help me if any
Best Regards
HanNguyen
Am 19.06.2011 09:31, schrieb Nhat Han:
Dear all,
I’m using ML605 board and downloading PCIe demo ( Gen2, x4 ) .
It’s attached to windows XP 32bit PC at Slot x16 PCI Express . When I check the
Configuration Space
the negotiated speed is only x1 but not x4 .
Do you know the reason ?
>
The PCIe basic spec only requires that both extremes of a slot are supported,
intermediate combinations are optional. In your case that means only x1 and x16
must be supported.
If your test system is a PC (so-called PC form factor), it should adhere to the
PCI Express card electromechanical spec. This states that all intermediate
configurations except x2 and x12 must also be supported. x2 and x12 are optional
(See section 6.3)
Note this only applies to CEM compliant systems (e.g. PCs). I have no idea what
the ML605 board is. Is that a PC or is it an embedded board (e.g. not necessarily
CEM compliant). If it’s a PC and doesn’t support CEM up-plugging, try and get your
money back, it doesn’t meet the spec 
> I asked PCISIG forum and they ask to check the mother board if
> it can support x4 . But I don’t know how to check .
>
You can check this in bits 9:4 of the Link Status Register in the PCI Express
Register Capability structure (offset 0x12 from start of PCIe Capability
structure). You’ll need your chip-set documentation to see where the capability
structure is located in configuration space. Again, no idea what chipset is on the
ML605 board.
> Beside, it’s ask to check if x4 is done but it changes to x1 for
> saving power . But I don’t have Bus capture for PCIe . I don’t know how to check also.
>
If you suspect this, try turning off ASPM in the BIOS. Windows XP doesn’t use this
feature anyway.
Regards,
Charles