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Altera_Forum
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13 years ago

FPGA Multiplication Resource Utilization

Hi, I need to do 18x7 multiplication and my FPGA doesnt have the built in DSP blocks, so I am using behavioral code in the source code to do the multiplication. It is taking around 190 LUT to do ...
Altera_Forum's avatar
Altera_Forum
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13 years ago

If you have some spare block-ram you can do full multiplication with two table look-ups, two additions and one subtract. This was used extensively on the commodore 64 for demos and boils down to:

F(a*b)=F(a+b)-F(a-b) where F is a table of squares divided by 4 ( i.e. x^2/4 )

Depending on your needs, pipelining should bring this down to a two-clock operation and minimal LE resources. An 8x8 multiplication would take 256 16-bit words of memory and 48 LE's ( 2x8 for lookups and 2x16 for pipeline registers ).

-Mux