Max clock rates in standard cell?

[off-topic, and sorry about the cross-post: there seem to be no NGs
which are relevant...]

I'm trying to get some idea of usable maximum frequencies at 90 -
130nm in standard cell. I have one ballpark estimate of about 300MHz
for 130nm, and 400MHz for 110nm, with ~4/5 levels of logic.

However, if I just add up raw gate delays, it seems that it should be
possible to go at about twice this speed. Does anyone have any better
estimates, or examples of faster chips? Is 800MHz+ achievable on 90nm,
or 600MHz on 110nm?

If not, any idea what the limiting factors are, and why clock rate
doesn't scale with logic levels? Is this down to silicon timing
uncertainties?

TIA -

Tim

Tim Neeson

On Fri, 23 Jun 2006 09:59:49 +0100, Tim Neeson <>
wrote:

>[off-topic, and sorry about the cross-post: there seem to be no NGs
>which are relevant...]
>
>I'm trying to get some idea of usable maximum frequencies at 90 -
>130nm in standard cell. I have one ballpark estimate of about 300MHz
>for 130nm, and 400MHz for 110nm, with ~4/5 levels of logic.
>
>However, if I just add up raw gate delays, it seems that it should be
>possible to go at about twice this speed. Does anyone have any better
>estimates, or examples of faster chips? Is 800MHz+ achievable on 90nm,
>or 600MHz on 110nm?
>
>If not, any idea what the limiting factors are, and why clock rate
>doesn't scale with logic levels? Is this down to silicon timing
>uncertainties?

I am assuming you're considering the setup times of the flops. Other
considerations are clock tree skew, clock jitter and power.
Effectively your minimum period is clk->Q+comb delay + clock skew +
jitter + setup. Of course you have to keep leakage and dynamic power
at a reasonable rate.
That said, if you limit your logic levels to 4 and have a decent
library, it is possible to achieve 500 MHz with 130nm and 800 MHz with
90nm but that requires quite a bit of effort (tight clock tree, manual
timing ecos etc.)

On Fri, 23 Jun 2006 16:15:16 GMT, mk<kal*@dspia.*comdelete> wrote:
<snipped>

Thanks - useful info.

Tim

> I have one ballpark estimate of about 300MHz for 130nm

Easy.

> >However, if I just add up raw gate delays, it seems that it should be
> >possible to go at about twice this speed.

Don't forget routing delay.

> Does anyone have any better estimates, or examples of faster chips?

ARM claim 333 - 550Mhz for ARM1136J-S in .13.

> Is 800MHz+ achievable on 90nm,

Yep.

Cheers,
Jon