Re: [SI-LIST] : How to identify SSO

D. C. Sessions (dc.sessions@tempe.vlsi.com)
Wed, 07 Jan 1998 17:33:42 -0700

Jon Powell wrote:
>
> My (probably redundant) take on SSO.
>
> One thing that has always concerned me with SSO is the affect of the VCC
> drop on non-switching signals. Theses signal would have noise on them
> that would mimic the VCC noise on chip (since their outputs are
> effectively shorted to VCC).

Jon, this is a Good Thing. IMHO, noise on quiescent outputs is a
lost cause. It's like Xline interconnect or near-end crosstalk
among bus lines: you AIN'T gonna get rid of it so you might as
well learn to make the best of the situation. Quiescent outputs
being (effectively) shorted to a rail, or at least a line at rail
potential, means that the active lines have one more dump for their
switching noise.

What causes ME to sweat nights is the fact that SSO causes driver
starvation. For the last couple of years it's the largest single
term in our clock-to-output timing.

-- 
D. C. Sessions
dc.sessions@tempe.vlsi.com