Gene, re: "Why doesn't Intel come out with a P55C 300/333?"
The short answer is that the P6 architecture is far more advanced
than Pentium and the circuits are engineered faster. The PII and
Celeron are today's products. The Pentium is obsolete.
With every generation of Intel product there has been this same
arguement. The question is asked by short sighted pundits, "Why
the change if the newer processor is almost as good and cost less?
Why didn't Intel just make a faster version the current processor?
The reason - The newer technology operates faster than the old.
The following is a partial list of the P6 enhancements to used to
attain performance:
Architecture enhancements (These have been well publicized)
- Separated cache bus - allows the cache hit speed to scale with
the processor core speed. Also removes cache traffic from the
system bus leaving generous bandwidth for main memory accesses.
- Greater efficiency - The sum of most of the internal
enhancements are here, such as branch prediction, out-of-order
execution, added execution units.
Circuit Enhancements - NOT publicized:
- Much deeper pipelines - The P6 does much less logic per
stage. This is called "critical path". A processor cannot
operate faster than its slowest critical path. The P6 has a
faster critical path than the Pentium.
- Improved power and clock distribution. - The P6 has more metal
devoted to power and clock, resulting in less power "droop" and
clock insertion losses.
- Much improved clock balancing. If a clock arrives at different
times inside a processor, the the chip can only work right using
the period from the slowest clock edge to the next quickest
clock edge. The P6 has much improved skew control allowing
more of each clock period for use by the logic.
Result: A P6 architecture chip will ALWAYS operate two speed grades
faster than a Pentium die all other things being equal.
Jeff
addendum:
--------------------------------------------------------------------
History As a reminder consider that,
The original 8086 was created by Intel at 4.7MHz Intel stopped at
6MHz. AMD hung on through 8MHz.
The '286 was introduced at 6MHz. Intel stopped at 12MHz. AMD hung
on through 20MHz.
The '386 was introduced at 16MHz. Intel stopped at 33MHz. AMD hung
on through 40MHz.
The '486 was introduced at 25MHz. Intel stopped at 100MHz, AMD hung
on through 120MHz. (DX4 at 40MHz).
The Pentium was introduced at 66MHz. Intel stopped at 233MHz - AMD
is still trying to get yield on their clone at 233MHz. Looks like
they will try to get it to at least 300MHz.
The P6 was introduced at 133 as the Pentium Pro. The PII product
yields well at 333MHz. In two weeks we will have 350 and 400MHz.
This summer will bring 450MHz.
------------------------------------------------------------------
Here is a table that covers even more x86 history:
CPU Type Date Speeds Number of Bus Maximum Cache
MHz Transistors Int/Ext Memory
8088 6-79 4.77,5,6 29K 16 / 8 1 MB none
80286 2-82 8,10,12,20 130K 16 / 16 16 MB none
80386SX 6-88 16,20,25,33 275K 32 / 16 16 MB none
80386SL 10-90 16,20,25 855K 32 / 16 16 MB 8 KB
80386DX 10-85 16,20,25,33 275K 32 / 32 4 GB none
80486SX 4-91 16,20,25,33 900K 32 / 16 4 GB* 8 KB
80486DX 4-89 25,33,50 1,200K 32 / 32 4 GB* 8 KB
80486DX2 3-92 25/50,33/66** 1,200K 32 / 32 4 GB* 8 KB
80486SL 9-93 25,33 1,400K 32 / 32 64 MB 8 KB
80486DX4 3-94 25/75,33/100 1,600K 32 / 32 4 GB* 8 KB
Pentium 3-94 66,75,90,100, 3,300K 32 / 64 64 TB*** 16 KB
120,133,150,
166,180,200,233
P Pro 1-96 133,150,180, 5,500K 64 / 64 64 TB*** 16 KB
p II 200,233,266,
300,333
* 4GB addressable, 64TB virtual memory
** External bus speed / Internal processor speed
*** 64TB addressable, 4PB virtual memory |
