Administrative Matters for Design and Architecture of Computer Systems | CS 161 | Assignments Computer Science

CS161: Design and Architecture of Computer Systems October 22, 2007

2004 Morgan Kaufmann Publishers

COMPUTER

SCIENCE & ENGINEERING

Administrative Matters

•Homework #3

–due Monday, 10/22

–Please read chapter 4 ahead of the lecture

•Midterm #1

–Wednesday 10/24

–Cumulative

• Chapter 1-4

• Homework 1-3

• Quiz 1-2

•Office Hour

–Tue 1-3PM (extra)

–Wed 12-1PM (moved)

–Tue 8-9AM (Ben)

–Wed 9-10AM (Edward)

2004 Morgan Kaufmann Publishers

COMPUTER

SCIENCE & ENGINEERING

Quick correction on homework3 solution

•4.10

–For C3, CPI for I1 is (.5*2+.25*3+.25*5)=3 and I2 has CPI

(.5*1+.25*2+.25*2)=1.5

–Using C3, I2 has 6/3= 2 billion instructions / second

–Using C3, I1 has 3/1.5= 2 billion instructions / second

2004 Morgan Kaufmann Publishers

COMPUTER

SCIENCE & ENGINEERING

2004 Morgan Kaufmann Publishers

COMPUTER

SCIENCE & ENGINEERING

Pentium bug

•Floating point division

•FDIV bug

–Lookup table to guess quotient based on divisor and di vidend

–Five elements were thought as “don’t care”

• Optimized away (return 0 instead of 2)

–They were wrong!!!

• Some error show up in 12-52 bits

• Or, 4

to 14

digit in decimal

2004 Morgan Kaufmann Publishers

COMPUTER

SCIENCE & ENGINEERING

Pentium-gate

•July, 1994

–Intel discover the bug

–Would cost $100,000’s to fix

–Months to verify

–New chip will ship January 1995

–3-5 million “bad” chip will ship

•September, 1994

–Thomas Nicely discover the bug, and posted on internet

•November 7, 1994

–Electronic Engineering Times front page

•November 22, 1994

–Intel call it a “glitch”,

–“errors in the ninth digit...even most engineers and financial analysts

require accuracy only to the fourth”

–“Affect only several dozen people in the world, we only heard of one”

–“Only theoretical mathematician should be concerned”

–Customer were told to describe their application to Intel, then Intel w ill

decide whether or not a new chip will be issued

2004 Morgan Kaufmann Publishers

COMPUTER

SCIENCE & ENGINEERING

Pentium-gate

•December 5, 1994

–Intel claimed

–“happen once in 27,000 years for typical spreadsheet user”

–“1000 divide/day 1/billion error rate, 9 million days = 27000 yrs”

–Number assume to be randomly distributed

•December 12, 1994

–IBM claimed

–“15 minutes calculation/day, 5000 divide/second, 4.2 million divide/day,

1/100milion error rate

–“happen once every 24 days”

–Immediately stop all shipment of IBM PC’s

•December 21, 1994

–Intel apologized

–Will correct affected processor anytime, no question asked

–Recall costs $500 million

–Intel employees did not get a Christmas bonus

Administrative Matters for Design and Architecture of Computer Systems | CS 161, Assignments of Computer Science

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Chapter 4

Assessing and Understanding Performance

(continue)

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=1.2 (400M*10)/6 = 800MHz

of cycles to execute program?

of instructions in program?

of cycles per second?

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