Having a hell of a time finding ICs that offer multiplication, subtraction and division?
Are these functions just a product of adders and not worth the fab?
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3\$\begingroup\$ Probably it's cheaper to use a microcontroller for such calculations, or if high speed is important, an FPGA. \$\endgroup\$– Michel KeijzersCommented Apr 28, 2018 at 11:26
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2\$\begingroup\$ There is no significant demand for such functions as stand-alone chips, so there's no economic incentive for anyone to make them. \$\endgroup\$– Dave TweedCommented Apr 28, 2018 at 11:36
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\$\begingroup\$ Subtraction can be done with an op amp; it's just addition with one signal inverted after all. Analog multiplication and division are a different matter, though. The AD633 is probably what you want, but there's so little demand (and the chip itself is so complex) that it's fairly expensive. \$\endgroup\$– HearthCommented Apr 28, 2018 at 11:43
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2\$\begingroup\$ Generally: It's always a good idea to give people at least a rough idea of what you're trying to do in the bigger picture. \$\endgroup\$– Marcus MüllerCommented Apr 28, 2018 at 12:20
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1\$\begingroup\$ A $1 PIC can do this easily. \$\endgroup\$– D.A.S.Commented Apr 28, 2018 at 15:10
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1 Answer
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I think there is some misconception in the question. To get something subtracted-added or multiplied, one has to feed operands, and store result, in some form. So a stand-alone ALU by itself is meaningless unless one builds the infrastructure and sequencers to perform these functions. Which is called "processor", or "CPU". And this "infrastructure" is usually much bigger and more complicated than the ALU itself. So yes, building an ALU alone is not worth it.
In the past, before the ability to build LSI - Large Scale Integrated circuits, there was a technology called "bit-slice", see Wikipedia article. Some remnants like SN74181 (by Texas Instruments) still can be found on e-Bay in vintage section, and probably few other chips from the Wikipedia list.
Today one can easily implement any kind of ALU using small FPGA, and even build full processors around.
answered Apr 28, 2018 at 18:29