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Date: Sun, 5 Jun 2011 01:39:51 +0400
From: Solar Designer <>
Subject: Re: EskBlowFish with RAM results

Hi Yuri,

I am sorry that I am somewhat late to comment on this...

On Tue, May 31, 2011 at 12:40:23AM -0300, Yuri Gonzaga wrote:
> I am reporting the synthesis results for EsksBlowFish using RAM to pico e101
> device (Spartan-6 xc6slx45).

Great!  Can you post the code, please?

> Slice Logic Utilization                   | Used | Available
> Number of Slice LUTs                                      8,059     27,288

Why so many LUTs?

> Number of occupied Slices                               2,611       6,822

This is a consequence of the above...

So we'd fit only 3 EksBlowfish cores into that Spartan-6 chip, resulting
in worse than CPU performance.  This shouldn't be so.

> Number of RAMB16BWERs                                 4             116

This makes more sense, but still I'd expect only 2 of these used.  Why 4?
Are you keeping the initial constants in separate BlockRAMs?  Or maybe P?
If so, the initial constants should be uploaded by the host, and P
should be in registers.

Anyhow, even at 4 16+2 Kbit BlockRAMs used per EksBlowfish, we could fit
29 cores in that chip.  So we're clearly LUT-bound now, in terms of the
number of cores we can fit.  Please look into reducing the LUT count,
which I think should be possible to reduce by a factor of 10 or more.
I really don't understand why you have so many LUTs used.



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