Re: How complex is the 6502?

[zcaa1122@rpool3.rus.uni-stuttgart.de (Wulf Hofbauer)]

In article <CGHLDo.EGG@actrix.gen.nz>,
David Empson <dempson@swell.actrix.gen.nz> wrote:
>In article <jpenne.753269520@ee.ualberta.ca> jpenne@ee.ualberta.ca (Jerry Penner) writes:
>So that means the 6502's ALU must have two alternative inputs for the
>second operand: one which presents the true value, and the other which
>presents the inverted value.  (It doesn't do the complement operation
>as a separate step, because it doesn't need an extra clock cycle to
>subtract instead of add).
>
>This means a set of eight inverters with tri-state outputs, I suppose.

This is generally achieved by gated exor inputs, and I believe these
are built into just about every ALU (the ALU structure is quite
standardized).

- Wulf

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| Wulf Hofbauer | zcaa1122@rpool1.rus.uni-stuttgart.de |
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