signed/unsigned multipliers

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You have chosen an example that works.

Now consider this: I want to multiply these two 3 bit values through same unsigned multiplier:

111 * 011 = ?

if viewed as unsigned, implies 7 * 3 = 21 [10101 correct]

if viewed as signed, implies -1 * 3 and should give -3

[ but 10101 is wrong now, means -11]

I don't know what you mean by sign extension here but let us try one bit extension:

0 111 * 0 011

7 * 3 = 21 0000 0000 10101 correct

1 111 * 0 011

15* 3 = 45 i.e. 101101 i.e./= -3

Correct ?, Wooooooo

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Let me correct myself, I got a bit flakey with numbers

let us assume the numbers are signed:

111 * 011 (as signed I expect the result to be -1 * 3 = -3

now sign extend according to tricky's trick:

111 111 * 000 011

the verdict:

= 10111101

and means -128 + 61 and /= the expected -3

So what is going on Now?