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Participant tmonaghan84
Participant
371 Views
Registered: ‎04-19-2018

PEtalinux DDR speed ZCU104

Hi

 

I am using a ZCU104 with PetaLinux 2018.2 and am seeing relatively slow DDR speeds.

 

On paper the DDR speed of the ZCU104 board is (DDR4-2400 64bit wide);

2 * 1200Mhz * 64bit = 153,600 MB/s = 150GB/s

 

Yet in PetaLinux using dd to copy to/from dev/zero I am getting;

Dev Zero -> Ram (write)

root@xilinx-zcu104-2018_2:/dev# time -p dd if=/dev/zero of=/tmp/testfile bs=256M count=2

2+0 records in

2+0 records out

real 1.18

user 0.00

sys 1.17

512 in 1.17s = ~437MB/s

(437MB / 150GB = 0.2% Efficiency)

 

RAM -> Dev Null (read)

root@xilinx-zcu104-2018_2:/dev# time -p dd if=/tmp/testfile of=/dev/null bs=256M count=2

2+0 records in

2+0 records out

real 0.62

user 0.00

sys 0.61

512MB in .62 = ~826MB/s

(826MB / 150GB = 0.53% Efficiency)

 

I am just wondering if these speeds are in the ball park of what we should expect?

I am I doing something wrong?

 

Thanks

Tim

 

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2 Replies
Moderator
Moderator
340 Views
Registered: ‎06-30-2010

Re: PEtalinux DDR speed ZCU104

I would be expected efficiency in the range of 80 - 95%, for the PL we have an efficiency table on age 19 https://www.xilinx.com/support/documentation/ip_documentation/ultrascale_memory_ip/v1_4/pg150-ultrascale-memory-ip.pdf

While its for the PL the PS controller is similar so would be in the same ballpark

The efficiency will change with the data pattern being used, what is the test you are running?
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Participant tmonaghan84
Participant
328 Views
Registered: ‎04-19-2018

Re: PEtalinux DDR speed ZCU104

Hi @jheslip, thanks for your reply.

 

I have spoken to a colleague who explained the benchmark I was doing was going through the filesystem and such would be limited by the O/S & CPU, in light of this the figures seem reasonable given the low power arm on the ZCU104.

 

Glad to hear the PL would achieve >80% efficiency.

 

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