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Visitor
Visitor
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Registered: ‎05-31-2020

checking the number of BRAM of pynq-z2 board for pragma hls loop unrolling

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Hi,

According to the following:

https://forums.xilinx.com/t5/High-Level-Synthesis-HLS/What-is-the-difference-between-unroll-and-pipeline/m-p/886038

 

it said 

Unrolling a loop with factor="N" means that HLS should create N copies of the processing hardware and run them in parallel. This has the advantage that it is possible to finish lots of iterations in every single clock cycle - I've had a block that did 54 iterations of a loop in one cycle. The disadvantage is that it takes a lot of hardware. If you're going to process 30 elements from an array at once, you need to be able to read 30 elements at once. Since Xilinx block RAMs have a maximum of two ports, this implies that you're going to need at least 15 block RAMs in parallel. If you don't have that, then HLS will construct a huge state machine so that your processing hardware gets sequential access to the RAM, which essentially drops you back to the un-unrolled performance while using 30 times as much hardware. As a result, unrolling only makes sense when you have (or can make) data structures that work with it. Other key requirements are that the extra hardware it generates (N sets of the processing hardware) is justified by the performance gain.

this above sounds like FPGA boards have a number of block rams.

however, when I tried to find the number of BRAM of pynq-z2 board, according to this link: http://www.tul.com.tw/ProductsPYNQ-Z2.html

it only tells that pynq-z2 has 630 KB of block ram

Are there multiple BRAM? how can I check whether a FPGA board has multiple BRAMs?

and can I exploit it for loop unrolling by using factor N as many BRAMs as possible?

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Voyager
Voyager
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Registered: ‎06-20-2012

Read the datasheet of ZYNQ XC7Z020-1CLG400C.

https://www.xilinx.com/support/documentation/data_sheets/ds190-Zynq-7000-Overview.pdf 

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Voyager
Voyager
278 Views
Registered: ‎06-20-2012

Read the datasheet of ZYNQ XC7Z020-1CLG400C.

https://www.xilinx.com/support/documentation/data_sheets/ds190-Zynq-7000-Overview.pdf 

== If this was helpful, please feel free to give Kudos, and close if it answers your question ==

View solution in original post