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

Jon Powell (jonp@pacbell.net)
Wed, 07 Jan 1998 17:41:07 -0800

D. C. Sessions wrote:
>
> 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

DC, this a Good Thing. If drivers are slow enough due to driver
starvation it prevents all of those SI problems. :)

jon