PCI-E Vendor Defined Messages

[Colin Hankins]

Does Windows support PCI Express Vendor Defined Messages? If so, what is the
mechanism for sending vendor defined messages in the ddk?

[Tim Roberts]

Post by Colin Hankins
Does Windows support PCI Express Vendor Defined Messages? If so, what is the
mechanism for sending vendor defined messages in the ddk?

No. Vendor-defined messages are a more-or-less useless part of the spec,
designed for things like bus extenders where the two ends need to
communicate with each other.

There's really no problem you can't solve using normal cycles.

[Colin Hankins]

That is disappointing. I thought it would come in usefull, from the host
system point of view, to send one message simultaneously (since the Vendor
Defined Messages allows for broadcast type routing) from the the host to
multiple cards in the PCI-E fabric. Yes, I can accomplish the same thing
with individual writes to each board, but one message would have been much
cooler and less bandwidth.

Thanks for the reply.

Post by Tim Roberts

Post by Colin Hankins
Does Windows support PCI Express Vendor Defined Messages? If so, what is the
mechanism for sending vendor defined messages in the ddk?

No. Vendor-defined messages are a more-or-less useless part of the spec,
designed for things like bus extenders where the two ends need to
communicate with each other.
There's really no problem you can't solve using normal cycles.
--
Providenza & Boekelheide, Inc.

[Tim Roberts]

Post by Colin Hankins
That is disappointing. I thought it would come in usefull, from the host
system point of view, to send one message simultaneously (since the Vendor
Defined Messages allows for broadcast type routing) from the the host to
multiple cards in the PCI-E fabric. Yes, I can accomplish the same thing
with individual writes to each board, but one message would have been much
cooler and less bandwidth.

It's more complicated than that. Remember that the processor doesn't
really speak PCIExpress directly. There is a translation, in the south
bridge. To do anything other than PCI-type transactions, you have to talk
directly to the root complex. There are multiple roots in the typical PC,
and there's no standard method for addressing them, so whatever you did
would only work on a few architectures.

The sad fact is that anything in PCIExpress that is not PCI-compatible is
never going to get widespread adoption. That includes isochronous and
virtual channels.

[Colin Hankins]

If I recall correctly, some of the Intel north bridge to south bridge
connections are very PCI-E like. In that they do have Vendor Defined
Messaging and Virtual Channels to support QOS and Isochronous transfers. I
assumed they would also extend this out the the actual PCI-E ports. Oh well.

Would you happen to know of any "high-end" systems that incorpoate root
complex chipsets that support full PCI-E specification (if there is such a
device)?

Again, thanks for the replies.

Post by Tim Roberts

Post by Colin Hankins
That is disappointing. I thought it would come in usefull, from the host
system point of view, to send one message simultaneously (since the Vendor
Defined Messages allows for broadcast type routing) from the the host to
multiple cards in the PCI-E fabric. Yes, I can accomplish the same thing
with individual writes to each board, but one message would have been much
cooler and less bandwidth.

It's more complicated than that. Remember that the processor doesn't
really speak PCIExpress directly. There is a translation, in the south
bridge. To do anything other than PCI-type transactions, you have to talk
directly to the root complex. There are multiple roots in the typical PC,
and there's no standard method for addressing them, so whatever you did
would only work on a few architectures.
The sad fact is that anything in PCIExpress that is not PCI-compatible is
never going to get widespread adoption. That includes isochronous and
virtual channels.
--
Providenza & Boekelheide, Inc.

[Tim Roberts]

Post by Colin Hankins
If I recall correctly, some of the Intel north bridge to south bridge
connections are very PCI-E like. In that they do have Vendor Defined
Messaging and Virtual Channels to support QOS and Isochronous transfers. I
assumed they would also extend this out the the actual PCI-E ports. Oh well.
Would you happen to know of any "high-end" systems that incorpoate root
complex chipsets that support full PCI-E specification (if there is such a
device)?

There aren't very many chipset makers. It shouldn't be too hard to check
them.

However, again I ask: what's the point? Your code is only going to work on
that chipset, and possibly even one version of that chipset. And, in the
end, you're talking about an utter micro-optimization. You're going to
invest days of effort in chasing down the mechanism and the possible
applicable chipsets, for the sake of saving a handful of nanoseconds.

It just doesn't make sense to me.

[m***@gmail.com]

Hi,

I have the same question now. Hope some support would have come atleast by now. Please let me know how can I send a VDM packet(MsgD) in application/driver to a PCIe device.

Thanks and regards,
Muthu