Re: Carry propagation, +, T=0 ???
- Subject: Re: Carry propagation, +, T=0 ???
- From: Penio Penev <penev@xxxxxxx>
- Date: Mon, 31 Mar 1997 19:20:31 -0500 (EST)
- cc: MISC
- In-Reply-To: <199704010010.QAA27386@geocities.com>
On Tue, 1 Apr 1997, Assen Kolov wrote:
> Penio Penev wrote:
> > As usual, I remind, that intructions execute in parallel, that is, if you
> > put a nop, the carry propagates behind the scenes. The instruction itself
> > _latches_ the result of the respective unit in TOS, that is you need nops
> > _before_ the "instruction".
>
> Thank you, this is indeed what happens - one should allow time
> _before_ executing +, not after. Just consider + as a latch.
>
> Let me quote again my manual from Offette enterprises, explaining +:
> "As the adder is implemented with ripple carry, the results of the
> addition will not be available immediately. The sum and the carry
> will be stabilized in the next word."
The manual may be vague, especially taking into account the non-standard
use of ALU instruction codes, i.e., latches. The subject itself has been
beaten to death at least 5 times, and has been asked at least 30 times.
This is by far rge most-F AQ. Someone should start writing :-)
--
Penio Penev <Penev@pisa.Rockefeller.edu> 1-212-327-7423