Pete, >Scumbria is not wrong.
Well then this guy is wrong:
Jeff Austin, Intel's IA-32 architect launch manager, said the Pentium 4's 20-stage pipeline suffers no penalty for pre-fetch misprediction because of its use of the NetBurst technology.
However, Jeff Austin has the luxury of going out to the lab and checking performance his engineers are seeing on real hardware. You guys are merely speculating.
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Intel Offers Details Behind Pentium 4's Speed
THURSDAY, AUGUST 24, 2000 11:30 AM
- TechWeb
Aug 24, 2000 (Tech Web - CMP via COMTEX) -- SAN JOSE, Calif. -- Countering claims made recently by an industry microprocessor research firm, Intel Corp. said the upcoming Pentium 4 has no deep pipeline performance penalty.
Intel (stock:INTC) executives at this week's Intel Developers Forum detailed the Pentium 4's NetBurst technology, which they said significantly increases performance over other processors, while nearly doubling the number of processor pipeline stages.
Jeff Austin, Intel's IA-32 architect launch manager, said the Pentium 4's 20-stage pipeline suffers no penalty for pre-fetch misprediction because of its use of the NetBurst technology.
Misprediction, which sounds like an arcane technical question, is a key performance factor. To increase the speed of operations and data rates, modern processors literally guess in advance what data will be needed.
If the processor guesses wrong, a deep 20-stage pipeline such as Pentium 4 can take up to 13 clock cycles to purge all the data and be refilled, slowing operations.
Bert McComas, an analyst at InQuest Research Inc., Gilbert, Ariz., claimed recently that the pre-fetch misprediction problem causes the 1.4-GHz Pentium 4 to operate at the same performance level as the 1.13-GHz Pentium III.
Austin, however, said NetBurst corrects most of the misprediction problem, with the Pentium 4 performing at the highest level of any processor to date from Intel, Santa Clara, Calif.
Allowing the deep Pentium 4 pipeline to meet performance targets is only one of NetBurst's goals, as the device also aims to provide much faster integer and floating-point-instruction operations.
NetBurst includes Advanced Dynamic Execution, a speculative engine that helps increase memory pre-fetch prediction rates greatly, according to Intel.
The technique uses three times as many instructions operating in pre-fetch as the Pentium III and includes more sophisticated algorithms that look at many prior executions before making a prediction on data to be accessed, Austin said.
The Pentium 4 also features a Level 1 on-chip cache that executes already decoded instructions, thus eliminating latency delays. The L1 cache of the Pentium III, in comparison, must decode instructions each time they are issued, slowing the speed at which data is fed to the processor.
NetBurst's Rapid Execution Engine is another feature and includes an ALU integer-processor running at 2.8 GHz, which is twice the main-processor clock speed and provides extremely rapid processing of integer instructions, Austin said.
A new Streaming SIMD-2 Extension in NetBurst also speeds processing by operating arithmetic integer operations at 128 bits every clock cycle, twice as fast as Pentium III. Additionally, Intel said, the NetBurst adds a 128-bit double precision float point operation not found in the Pentium III.
techweb.com
Copyright (C) 2000 CMP Media Inc.
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