[Cryptech Core] Xilinx Zync devices for possible next Cryptech HSM

[Joachim Strömbergson]

Aloha!

On 2018-10-30 14:24, Peter Stuge wrote:
> Joachim Strömbergson wrote:
>> Zync
> ..
>> The much higher clock speed of the integrated ARM cores, low latency
>> on-chip memory and esp wide, low latency interfaces between the CPU and
>> FPGA would allow very much higher performance than what we can reach on
>> the current Alpha board. (The maximum clock frequency of the cores in
>> the FPGA would not increase substantially.)
> 
> Let's go into more detail about this.
> 
> Please clarify exactly what allows performance gains, if core clock
> stays near same order of magnitude?

The time to transfer data between CPU and FPGA can be improved several
times. By doubling the bus width, increasing bus clock speed, by using
block transfers in the AXI bus. We can achieve some of this (block
transfer) to some degree on the Alpha (see previous mail regarding
performance.). The Zynq even supports memory sharing between CPU and
FPGA parts to remove copying. Today we do *a lot* of transfer over the
FPGA bus.


> If cores are currently generally idle then don't we in fact just have
> a pipelining/scheduling problem, as opposed to a latency problem?

No. Not only, they aren't mutually exclusive problems. The cores can be
idle due to processing in the MCU, and the cores can be slow.


> Yes, the bare metal software environment on the M4 is a bit lame,
> but it also does not have a whole lot to do.

Well, the M4 actually ha quite a lot do do. And for some use cases
definitely seems to dominate the performance. For those parts a close to
6x increased clock speed would improve performance. Lower access latency
to the memory will also improve SW performance. But see more below.


> What are the actual bottlenecks?

That is a very good question. I posted a pretty lengthy email with some
analysis and more questions related to current status of the performance
improvements, profiling etc. With a flurry of zero responses.

-- 
Med vänlig hälsning, Yours

Joachim Strömbergson
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