11-18-2019, 09:22 PM
http://files.pine64.org/doc/rockpro64/ro...21-SCH.pdf
"PCIe x4"-page 27
Please refer to the above page
What we want to pay attention to is the series of parts attached to the signal "PCIE_RX3P / PCIE_RX3P".
(These parts are not a typographical mistake in the circuit diagram. These parts are actually mounted.)
----
I would like to ask someone with hardware experience.
Is it allowed to add such parts to high-speed signal lines that require strict impedance matching?
In the first place, what is the significance of adding these parts?
If such a component is added to a high-speed signal line such as "PCIEx"
The signal amplitude that passes is greatly reduced, and it can be presumed that the eye pattern at the receiving end will be severe.
And all cards of type "x4" are actually affected.
For example, "nvme", but it goes without saying that the impact is not limited to this.
I own 3 "rockpro64" units. (2 units are unstable or limited)
And I actually removed the parts described above for these.
The result is as expected,
It was confirmed that all three units were operating stably, including two units that were originally unstable (crash or limited-Link).
---
Another product, for example:
"pinebookpro_v2.1_mainboard_schematic.pdf"
Does not include the parts described above.
And it is the same for other manufacturers.
From this, it is clear that these additional parts are not due to restrictions in "RK3399".
I think it is a complete mistake in circuit design.
Perhaps they forgot to remove the parts that were added for operation verification at the prototype stage.
"PCIe x4"-page 27
Please refer to the above page
What we want to pay attention to is the series of parts attached to the signal "PCIE_RX3P / PCIE_RX3P".
(These parts are not a typographical mistake in the circuit diagram. These parts are actually mounted.)
----
I would like to ask someone with hardware experience.
Is it allowed to add such parts to high-speed signal lines that require strict impedance matching?
In the first place, what is the significance of adding these parts?
If such a component is added to a high-speed signal line such as "PCIEx"
The signal amplitude that passes is greatly reduced, and it can be presumed that the eye pattern at the receiving end will be severe.
And all cards of type "x4" are actually affected.
For example, "nvme", but it goes without saying that the impact is not limited to this.
I own 3 "rockpro64" units. (2 units are unstable or limited)
And I actually removed the parts described above for these.
The result is as expected,
It was confirmed that all three units were operating stably, including two units that were originally unstable (crash or limited-Link).
---
Another product, for example:
"pinebookpro_v2.1_mainboard_schematic.pdf"
Does not include the parts described above.
And it is the same for other manufacturers.
From this, it is clear that these additional parts are not due to restrictions in "RK3399".
I think it is a complete mistake in circuit design.
Perhaps they forgot to remove the parts that were added for operation verification at the prototype stage.