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switching between Altera and Xilinx

 
 
bobrics
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      02-19-2005
Hi,
I have some experience with Xilinx FPGA's and Webpack tool. I was
thinking about doing some project for fun at home and found Pluto board
that uses Altera FPGA.

Is it easy to jump from one system to another one in terms of learning
time?
Do architectures differ a lot, so that if I would like to adapt the
code for Xilinx Spartan or Virtex chip, will I need to do a lot of
changes?

Thanks

 
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Jezwold
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      02-20-2005
The only real differences will come if your xilinx secific code
directly instantiates devices which are built into the fpga fabric such
as multipliers,lsr16s or DCMs etc.I have found that in most cases its
fairly easy to migrate code between the two manufacturers.Obviously
your performance will take a big hit you you make heavy use of such
'built in' xilinx features.

 
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bobrics
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      02-21-2005
Thanks for the reply.

If you use multipliers in Xilinx by instantiating certain components,
then you could probably instantiate similar component in Altera.

Are their architectures pretty similar, comparing device families?

 
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Jerry Coffin
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      02-21-2005
bobrics wrote:
> Hi,
> I have some experience with Xilinx FPGA's and Webpack tool. I was
> thinking about doing some project for fun at home and found Pluto
> board that uses Altera FPGA.
>
> Is it easy to jump from one system to another one in terms of
> learning time?


There are really two parts to this: one is the tools, and the other is
the devices themselves.

The tools are pretty comparable -- to me, Quartus seems more
integrated, where ISE is more a collection of individual pieces. For
example, in Quartus, you have one place that you setup things like the
colors for almost any tool, where ISE has a separate setup screen for
each individual tool. Quartus also supports Tcl, so you can create your
own toolbar buttons and assign scripts to them. Then again, I've never
really used this, and never particularly missed it in ISE either.

The hardware depends a lot on which exact chips you compare -- the
Pluto board seems to use an Acex 1K part, which is fairly comparable to
a Xilinx Spartan 2. If you're using to something newer (e.g. a Spartan
3) your design might easily use features it's missing, so you may have
to write your own logic for them, and/or lose some performance. OTOH,
if you've used mostly older Xilinx parts (e.g. the original Spartan)
you'll probably find some new features you didn't get to play with
before (unfortunately, my memory that far back is slightly undertain,
so I'm hard put to say more about this with certainty).

Most typical code, however, works about the same with one as the other.
I've never tried to do a careful comparison, but as a general
impression the comparable Altera parts generally seem a little faster
than their Xilinx counterparts.

--
Later,
Jerry.

The universe is a figment of its own imagination.

 
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Jezwold
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      02-21-2005
Xilinx and Alera seem to match each other pretty evenly and have
equivelents for each others families.Altera have multipliers which are
almost exactly the same as ones found in xilinx parts for
example.However much of the time if I am using a multiplier for example
I let the synthesis tool infer it from the hdl rather than specifically
instantiate it .

 
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bobrics
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      03-07-2005
So, for multiplication you are using SIGNAL1 * SIGNAL2 format and let
synthesis tool decide itself what to do?

A bit out of topic, but is using multiplication sign efficient?

 
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