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xifengw
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Registered: ‎04-10-2019

Using 8H Stack HBM

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Hello,

I have some questions about using HBM. I want to choose the two stack HBM. The VIVADO version is 2019.1  It can be seen from the manual that the selection of HBM should be 34 address bits wide at 8H, but it is only 33 bits wide in actual use, which makes me unable to assign the port address of HBM correctly. Is the manual version not updated yet?

In addition, an HBM pseudo-channel should be 256M, but the manual says "8H Stack[28:5] are used to access the actual HBM memory", which means a pseudo-channel is 512MB.

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necare81
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Registered: ‎03-31-2016

A VU37P does NOT have an option for an 8H stack.  You can choose to use either one or two separate 4H stacks in that device.  You CANNOT do 8GB in a single stack with that device.

The documentation you are looking at also covers the real 8H stack in the VU47P and VU45P devices which have 2 separate 8H stacks giving a total of 16GB of memoy.

You can get 8GB of memory two ways, which one applies to  you depends on which device you have, and the address mapping depends on which way you chose

a VU47P will do 8GB as a single 8H stack.

Your VU37P will do 8GB as two 4H stacks.

VU37P  8GB != 8H stack.

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rpr
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Registered: ‎11-09-2017

Hi @xifengw 

Your understanding is correct, HBM GUI address map appearing as 27 downto 5 but it should be 28 downto 5.

IP outputs are good i.e., source code is good however GUI is showing as 27 downto 5. Issue get fix in vivado 2020.1

Regards
Pratap

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xifengw
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Registered: ‎04-10-2019
I now understand that the GUI made the mistake of displaying a 34bit as a 33bit.But maybe I haven't made myself clear.I think there are also errors in the manual description.

If I choose 8H stack, HBM will have 32 AXI ports,it should be 32 downto 28, and each AXI will access 256MB below.But according to the documentation, HBM will have 16 AXI, each accessing 512MB.

I want to know the correct understanding.
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rpr
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Registered: ‎11-09-2017

Hi @xifengw 

Let me clarify, xilinx provides two types of memory stacks 8GB and 16GB.

Total available 8GB, selection is available 4GB left, 4 GB right or total available memory 8 GB - example XCVU37p.

similarly for16GB also selection is available 8GB left, 8 GB right or total available memory 16 GB - example XCVU47p.

Both 8GB and 16 GB have 16 memory controllers and two AXI ports per memory controller. Each AXI port has fixed address map of 2 Gb (4H Stack) or 4 Gb (8H Stack)

Regards
Pratap

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xifengw
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I don't think so. I'm using XCVU37p, the maximum memory is 8GB. If I pick one stack, there are only 8 memory controllers, compared to 16 memory controllers when I use 8H stack.

With 8H STACK there are 32 AXI ports, so each is 8GB/32=2Gb = 256MB.

微信图片_20200529230445.png
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necare81
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Registered: ‎03-31-2016

A VU37P does NOT have an option for an 8H stack.  You can choose to use either one or two separate 4H stacks in that device.  You CANNOT do 8GB in a single stack with that device.

The documentation you are looking at also covers the real 8H stack in the VU47P and VU45P devices which have 2 separate 8H stacks giving a total of 16GB of memoy.

You can get 8GB of memory two ways, which one applies to  you depends on which device you have, and the address mapping depends on which way you chose

a VU47P will do 8GB as a single 8H stack.

Your VU37P will do 8GB as two 4H stacks.

VU37P  8GB != 8H stack.

View solution in original post

xifengw
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Registered: ‎04-10-2019

Thank you very much for solving my question.

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