Floorplanning, Routing, FPGA Editor

In wanting to gain a greater understanding of routing options (particularly as related to making floorplanning decisions) I find myself studing devices in the FPGA Editor. One question that occured to me is: How accurate a representation of the actual device layout does this tool provide? Example:

I'm looking at an XC2V100-4FG456. I see that all embedded multipliers have the I/O on the left side only. Obviously all PIP's are on that side as well. And there are four switch boxes that would seem to be the best place to connect in/out of the multipler. These switch boxes, in turn, would be the way to access the CLB's to the immediate left and right(through their own switch boxes). Double interconnect lines seem to be the best possible path.

Are these accurate representations of the geometry? Accurate enough to decide, for example, that the path from a multiplier, through its switch box, via a double line, into the CLB to the left is slightly faster than using the same double line to go to the CLB on the right?

Can any sort of assumptions be made in terms of ps per unit length from what is seen in FPGA Editor? What's the cost (delay wise) of going through a PIP FET?

Is this the wrong approach to making floorplanning decisions?

Thanks,

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Martin Euredjian
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Martin Euredjian
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Sorry, XC2V1000

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Martin Euredjian
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Martin Euredjian

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--Ray Andraka, P.E. President, the Andraka Consulting Group, Inc.

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Ray Andraka

Cannot answer your question, but thought I would bring to your attention Xilinx XAPP636, "Optimal Pipelining of I/O Ports of the Virtex-II Multiplier", in case you have not seen it.

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PIP

Reply to
Barry Brown

Yes, I have, thanks. I show that I downloaded it back in December '02. Re-studied it a few days ago.

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Martin Euredjian

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--Ray Andraka, P.E. President, the Andraka Consulting Group, Inc.

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Ray Andraka

multipliers in

Right. I experimented with the XAPP636 placement and studied the routing in and out of the multiplier with FPGA Editor. Makes sense. Can't see a faster way to lay it out.

Funny enough, if you let the tools do a layout they will be exceedingly happy to put FF's so far away from multipliers that a monkey with a dart might be able to do better. This, I don't really understand.

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Martin Euredjian

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--Ray Andraka, P.E. President, the Andraka Consulting Group, Inc.

401/884-7930 Fax 401/884-7950 email snipped-for-privacy@andraka.com
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"They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759

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Ray Andraka

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