Re: How does PCIe appear to the host?

[mlelstv%serpens.de@localhost (Michael van Elst)]

mouse%Rodents-Montreal.ORG@localhost (Mouse) writes:

>I note a possible conflict between the "x1" and the presence of a x16
>slot; that 1 is coming from the PCIE_LCAP_MAX_WIDTH bits in PCIE_LCAP,
>which makes me wonder whether something needs configuring to run the
>x16 slot at more than x1.  The card does say it needs a x4 or higher
>slot to work, so if the x16 slot is running x1 (is that even possible?)
>that might be responsible.

If the card requires x4 and you only have x1 it will not work.

PCIe cards generally are supposed to also run with fewer lanes, but
some older or more esoteric cards will not negotiate this.


>One of these machines is an ASRock Q1900M.  It has only two SATA ports
>onboard; it has two PCIe x1 slots and a PCIe x16 slot.  I just today
>picked up a 5-port PCIe SATA card and tried it.

The J1900 SoC on that board only provides 4 PCIe lanes.

While the SoC does also support x4 and x2 configurations, your
board is limited to the three slots with one lane each, and
the fourth lane is used for the RTL8111 ethernet chip.

I use a

ahcisata2 at pci2 dev 0 function 0: Marvell 88SE9215 SATA Controller (rev. 0x11)

card in a x16 slot with also only one lane. It provides 4 SATA ports.
The 88SE9215 is a ahcisata compatible controller (unlike older Marvell
chips that require their own driver and have some problems).

I also have a

jmide0 at pci1 dev 0 function 0: JMicron Technology JMB363 SATA/PATA Controller (rev. 0x03)

similar in a x4 slot with only one lane. It provides two SATA ports
and a PATA port that I use for an old DVD writer.