On 6/23/07, Andrew Lentvorski <[EMAIL PROTECTED]> wrote:
The second part of the problem is that the trace length between the
processor and the memory is somewhere in the range of 15-30cm. This is
on the order of 1/2 to 1ns even at the speed of light (and the electrons
do not move at that speed in copper). Even if you had a RAM latency of
0, sending the command and getting the response is limited to about 1ns
in latency. That means that we have about a 2-3 to 1 CPU to memory
mismatch that can never be fixed other than by parking memory right on
the CPU.
Reality check. I haven't seen a computer in which the processor and
memory were 6 to 12 inches apart (15 to 30 cm) since late PDP11 days
(mid 1980's).
Another reality check. The speed of electromagnetic wave propagation
in copper is considerably faster than the speed of the electrons.
carl
--
carl lowenstein marine physical lab u.c. san diego
[EMAIL PROTECTED]
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