Re: RC5 algorithm .... Re: "success"

	david fleischer <cilantro_il-/[email protected]> on Thu, 19 Oct 2006 00:31:36 wrote:
	> Subject: Re: [Hardware] "success"
	> To: "John L. Bass" <jbass-/[email protected]>
	> 
	> Martin,
	> What is YOUR estimate?
	> 
	> Regards,
	> David

I suspect this is where the 40K LUT number came from in Martin's comments:

>From jbass Fri Dec 30 16:39:34 2005
>To: jbass-/[email protected], [email protected]
>Subject: Re: FPGA C code
> 
>         I'm sure I can get ISE 4.2 from the Xilinx website. I forgot you told me
>         previously that I needed to convert the XNF to EDF. I've used EDF before
>         to go from Synplicity to ISE. You mention the Virtex parts. Is it not
>         possible for some reason to put this on a Spartan 3? The reason is that
>         I have a Spartan 3 - 200 board right now.
>         I took a VLSI class last semester, so that is my interest for the RSA
>         project. It is mainly personal.
>         I could write a converter for xnf2edf if it isn't too difficult. I don't
>         know the specifics of either format but I have experience in perl. I
>         have two weeks before classes start up, at which point my time will be
>         severely limited.
> 
> As long as the Spartan 3 has enough LUTs and can route the resulting net
> should not be a problem. A Spartan 3 has 8 LUT's per CLB, so you will need
> a device with about 10% more than 36,000/8 = 4500 CLB's. From the data sheet
> the smallest device is an XC3S2000 with 5120 CLB's which should be more than
> enough headroom to get the device routed. There may not be enough room to
> pipeline it, as the additional LUT rams may run you over budget.
> 
> It took HOURS to route it on my 533MHz PII last year, before it reached timing
> closure. So expect it might be slow going.
> 
> A fully pipelined RSA network requires 102 barrel shifters that are 32 bits
> wide. With lut based hand design this would result in lut muxes 5 deep with
> a log2 pattern.  102*32*5 = 16,320 LUTs for barrel shifters. This can be
> reduced for some FPGA's by using H 3-LUTs in XC4K's, and F5 muxes in Virtex
> devices. There are another 4-5 32 bit adders per stage, which require another
> 16K LUTs. Using 32x1 LUT rams for pipeline retiming S and L, adds four
> additional LUTs per stage. To provide framework logic, and additional redundant
> logic to reduce fanout costs another few percent in space.
> 
> If you order the mux right, you can combine it with the first adder stage and
> save a few LUTs. The best hand design I've done, which didn't have the best
> timing, was only 15-20% smaller than this.
> 
> It's why I commented it takes a pretty fair sized fpga. I was using XCV2000E's,
> XCV2600E's, and XC2V6000's.
> 
> The xnf to edf project is a feature request on the fpgac site:
> 
> http://sourceforge.net/tracker/index.php?func=detail&aid=1365849&group_id=152034&atid=782959
> 
> Which has an example of both netlist formats. I'm working on a generalized
> netlist format as the std backend for FpgaC, that I'm calling cnf. It's not
> nearly as verbose. If you need to write a converter, I'll send you a working
> copy of fpgac that has cnf output.
> 
> This is a fun project, and good experience fitting real world type applications
> to hardware.
> 
> Have Fun!
> John
> 
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