Interesting 1970's IC

[cadet1620]

I was looking up some info in one of my IC databooks and randomly opened on an interesting part.  The 74H87 implements the front-end processing for the ALU.  You might find the 74H87.pdf datasheet interesting.

Maybe if I get bored I'll do a 7400 series design for the ALU.  Back of the envelope estimate is 30 ICs, about 20 square inches of PCB allowing for I/O and power supply connectors.

--Mark

[ybakos]

Hi Mark,
I finally got a chance to take a look at this. I'm curious -- what do you mean by "the 74H87 implements the front-end processing for the ALU?" I'm looking at the datasheet and my eyes are glazing over.

[cadet1620]

Here's the function table for the 74H87. Note L=FALSE, H=TRUE.

   Ctrl in |      Outputs
    -------------------------
     B  C  |  Y1  Y2  Y3  Y4
    -------------------------
     L  L  | !A1 !A2 !A3 !A4
     L  H  |  A1  A2  A3  A4
     H  L  |  H   H   H   H
     H  H  |  L   L   L   L

This chip implements 4 bits of the zx/nx circuit, so 4 of these chips would be needed for the x input processing. The B control input is the zx input; the C input is needs inverted nx. Y channel would require another 4 'H87s.

--Mark

[ybakos]

Ah, I see it now. Thanks for sharing that.