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Date: Wed, 16 Jul 2014 13:34:39 +0200
From: Katja Malvoni <kmalvoni@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: ZedBoard: bcrypt

ᐧ
Hello,

I implemented 35 instances of bcrypt on ZedBoard where each instance uses 3
BRAMs and computes single bf round in one clock cycle. 2 BRAMs are used to
store S-boxes and 1 BRAM to store other data (P-box, expanded key, salt and
cost). Clock frequency is 71 MHz. Utilization is:
Number of Slice Registers:                     5,911 out of 106,400    5%
Number of Slice LUTs:                         27,837 out of  53,200   52%
 Number of occupied Slices:                  10,584 out of  13,300   79%
Number of RAMB36E1/FIFO36E1s:           105 out of     140   75%

Performance is 3346 c/s (40.58 c/s for cost 12). It is lower than expected
(I expected it will be bit more than 3754 c/s which was achieved with 70
instances, 2 clock cycles per bf round). If I measure time, communication
time is 4 ms while computation time is bit more than 6 ms. This gives ~3500
c/s which is more than 3255 c/s (1/((4+6)/1000/35). I don't know where this
other time is spent.

If I fully use BRAMs, 46 instances fit. Performance in that case is 4075
c/s (with -te=50). For cost 12 it is 53.28 c/s. Clock frequency is 71 Mhz,
utilization is:
Number of Slice Registers:                     6,825 out of 106,400    6%
Number of Slice LUTs:                         35,877 out of  53,200   67%
Number of occupied Slices:                  11,129 out of  13,300   83%
Number of RAMB36E1/FIFO36E1s:           138 out of     140   98%
(everything was tested on the "zed" system)

I'll implement 56 instances with 4 BRAMs per core and see if these will
perform as expected.

Katja

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