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[DPRG] Families

Subject: [DPRG] Families
From: Dan Miner miner at centtech.com
Date: Thu Jun 28 11:54:14 CDT 2001

CMOS transistors are used in all modern CPUs(*).  The apparent
discrepancy comes from the fact that the biggest slow-down to
any chip is driving the package pin.  If the interconnect 
technology existed (at a reasonable price and reliability) to
just connect silicon dice to other dice, then the speeds would
be much higher.  As Clay outlined, CPUs like Pentium run with
internal clock speeds far greater (~1GHz) than their bus or 
pin speeds (133MHz or sometimes 266MHz now).  This is because
the package pins have much more capacitance (and inductance and
resistance) than wires that connect individual transistors on
the same chip.

				- Dan Miner

(*)Footnote - Yes, there are some military and networking processors
that are not made with CMOS but they are such low volume and high
cost that I'm not counting them here.

> -----Original Message-----
> From: R. Bickle [mailto:rbickle at swbell.net]
> Sent: Thursday, June 28, 2001 11:32 AM
> To: 'Kipton Moravec'
> Cc: 'DPRG List'
> Subject: RE: [DPRG] Families
> Kip,
> All true. But I wonder what family of logic is employed in 
> the logic. I know
> that the processor cores utilize MOSFETs and not BJTs for 
> switching. Most of
> the heat is generated in the actual switching currents due to 
> MOSFET gate
> capacitance - a problem that gets worse and worse with 
> increased frequency.
> Question is: If in discrete components the fastest CMOS logic can only
> switch at 2nS (FACT family from Mike's table) which 
> translates to 500MHz,
> what is being used in 1GHz processors?
> Rick

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