cpu pins -> architecture correlation? (beginner question)

[kilik3000]

I'm curious about how the number of pins on a cpu correlates to
underlying architecture. For example on a picture of an old 8086 I
counted 40 pins. From what I've read the 8086 was an 16 bit
architecture. The 80386 had 68 pins. From what I've read this chip
was the first from Intel to support 32 bits.

Is there a correlation between the number of pins on a cpu and the
architecture it will support (8bit, 16, 32, etc.)? If so - what is the
correlation?

-Thx

 

[Scott Alfter]

Is there a correlation between the number of pins on a cpu and the
architecture it will support (8bit, 16, 32, etc.)? If so - what is the
correlation?

Not really. The 6502 is an 8-bit processor and the 65816 is a 16-bit
processor, but both come in the same 40-pin DIP package. For a (slightly)
more modern example, compare the 286 (16-bit) and 386SX (32-bit).

For a more current example, consider the Socket 775 processors that are
available with (Core 2) and without (Pentium 4) 64-bit support.

_/_
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[Robert Redelmeier]

Is there a correlation between the number of pins on a
cpu and the architecture it will support (8bit, 16, 32,
etc.)? If so - what is the correlation?

There used to be a _very_ rough correspondence. Once you
take into account duplexing address and data pins, more
bits required more pins. Now there really isn't since most
of the pins are for power or ground.

-- Robert

 

[johannes]

Not really. The 6502 is an 8-bit processor and the 65816 is a 16-bit
processor, but both come in the same 40-pin DIP package. For a (slightly)
more modern example, compare the 286 (16-bit) and 386SX (32-bit).

The 386SX had memory connection multiplexed into a half-witdh 16 line bus,
that also made motherboards simpler and cheaper.

For a more current example, consider the Socket 775 processors that are
available with (Core 2) and without (Pentium 4) 64-bit support.

The high number of pins on modern chips is really staggering. However, many
pins are used for power supply, delivering 50Amp or more into the chip.

 

[Yousuf Khan]

I'm curious about how the number of pins on a cpu correlates to
underlying architecture. For example on a picture of an old 8086 I
counted 40 pins. From what I've read the 8086 was an 16 bit
architecture. The 80386 had 68 pins. From what I've read this chip
was the first from Intel to support 32 bits.

Is there a correlation between the number of pins on a cpu and the
architecture it will support (8bit, 16, 32, etc.)? If so - what is the
correlation?

Nope, no correlation. The 68-pin 386 may have been a 32-bit processor,
but so were most of its successors upto and including the 771-pin
Pentium 4 and 472-pin Athlon XP. So there was upto an 11-fold increase
in pins without any corresponding upgrade in "bittedness".

Yousuf Khan

 

[Trent]

Nope, no correlation. The 68-pin 386 may have been a 32-bit processor,
but so were most of its successors upto and including the 771-pin
Pentium 4 and 472-pin Athlon XP. So there was upto an 11-fold increase
in pins without any corresponding upgrade in "bittedness".

Yeah, they are 32 bit processors, but the Pentium and higher have a 64 bit
data bus.