Edin,
I think you've got that about right.
There are EDA tools that can analyze serial links for compliance with
applicable protocols, and some can handle the case you're describing, where
you're only designing part of the link and need a model supplied for the rest.
PCIe-3 is an end-end spec, so you need to model and analyze a complete link.
If it were me, I'd start with PCIe-3 Compliance Analysis, since that's fast,
easy and predictable. I *might* run an IBIS-AMI simulation if I thought the
margins were tight, but since the design is an add-in card and you don't know
much about the motherboard other than the loss target, I'd probably just stick
with Compliance. IBIS-AMI models are meant to represent specific components
and equalization settings, and if you don't know what the motherboard component
will be - it's just conjecture.
Todd.
Todd Westerhoff
High-Speed Design Product Marketing | Electronic Board Systems (EBS)
Siemens EDA
300 Nickerson Rd, Marlboro, MA 01752
todd.westerhoff@xxxxxxxxxxx | office: 508-303-5821 | cell: 978-846-0203
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf Of
Edin Bazo
Sent: Sunday, May 23, 2021 12:44 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] PCIe simulation between an off-the-shelf motherboard and
custom PCIe card with custom riser card
Hi All,
I am going to design a custom PCIe gen3 card and a riser card for this PCIe
card.
The custom PCIe gen3 card (A) will be plugged into a custom riser card (B) and
then plug this riser card into a PCIe slot of an off-the-shelf motherboard (M).
From what I understand, the budget of the insertion loss (IL) of PCIe is 22dB
for Gen3, 6.5dB for a standard Add-in Card (AIC).
An off-the-shelf motherboard supports a standard AIC, so the worst-case
scenario IL for an off-the-shelf motherboard would be 15.5dB include PCB of
motherboard and CPU package, PCIe connector.
Am I understanding this correctly?
Since I don't have the motherboard model of an off-the-shelf motherboard, I
would need to create a model (S-parameter) of an off-the-shelf motherboard for
simulation with the custom PCIe card and custom riser card that I am going to
design.
There would be two options that I am considering as below:
1) Create an S-parameter for a motherboard with IL=15.5dB and simulate with the
custom PCIe card + custom riser card.
I need to make sure the IL of custom PCIe card + custom riser card < 6.5dB.
I'm considering this is a worst-case scenario and my custom PCIe card + custom
riser card should work with any motherboard in the market.
2) Create an S-parameter for the motherboard where the IL of the motherboard +
IL of my custom riser card = 15.5dB.
In this case, the IL of the motherboard will be less than 15.5dB and I have to
find an off-the-shelf motherboard that has IL <= 15.5dB - IL of my custom riser
card.
I think it is very difficult to find this motherboard since it is not easy to
get the IL of the motherboard from the vendor.
If you would simulate the above PCIe link, which option would make sense?
I appreciate your advice!
Thanks,
Edin Bazo
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