{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

slide13 - Memory Subsystem and Cache Adapted from lectures...

Info icon This preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
Memory Subsystem and Cache Adapted from lectures notes of Dr. Patterson and Dr. Kubiatowicz of UC Berkeley
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The Big Picture Control Datapath Memory Processor Input Output
Image of page 2
Technology Trends DRAM Year Size Cycle Time 1980 64 Kb 250 ns 1983 256 Kb 220 ns 1986 1 Mb 190 ns 1989 4 Mb 165 ns 1992 16 Mb 145 ns 1995 64 Mb 120 ns Capacity Speed (latency) Logic: 2x in 3 years 2x in 3 years DRAM: 4x in 3 years 2x in 10 years Disk: 4x in 3 years 2x in 10 years 1000:1! 2:1!
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Technology Trends [contd…] µProc 60%/yr. (2X/1.5yr) DRAM 9%/yr. (2X/10 yrs) 1 10 100 1000 1980 1981 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 DRAM CPU 1982 Processor-Memory Performance Gap: (grows 50% / year) Time “Moore’s Law” Processor-DRAM Memory Gap (latency) “Less’ Law?”
Image of page 4
The Goal: Large, Fast, Cheap Memory !!! Fact Large memories are slow Fast memories are small How do we create a memory that is large, cheap and fast (most of the time) ? Hierarchy Parallelism
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
By taking advantage of the principle of locality: Present the user with as much memory as is available in the cheapest technology. Provide access at the speed offered by the fastest technology. Control Datapath Secondary Storage (Disk) Processor Registers Main Memory (DRAM) Second Level Cache (SRAM) On-Chip Cache 1s 10,000,000 ns (10 ms) Speed (ns): 10ns 100ns 100s Gs Size (bytes): Ks Ms Tertiary Storage (Tape) 10,000,000,000ns (10 sec) Ts
Image of page 6
Today’s Situation Rely on caches to bridge gap Microprocessor-DRAM performance gap time of a full cache miss in instructions executed 1st Alpha (7000): 340 ns/5.0 ns = 68 clks x 2 or 136 instructions 2nd Alpha (8400): 266 ns/3.3 ns = 80 clks x 4 or 320 instructions
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Memory Hierarchy (1/4) Processor executes programs runs on order of nanoseconds to picoseconds needs to access code and data for programs: where are these? Disk HUGE capacity (virtually limitless) VERY slow: runs on order of milliseconds so how do we account for this gap?
Image of page 8
Memory Hierarchy (2/4) Memory (DRAM) smaller than disk (not limitless capacity) contains subset of data on disk: basically portions of programs that are currently being run much faster than disk: memory accesses don’t slow down processor quite as much Problem: memory is still too slow (hundreds of nanoseconds) Solution: add more layers ( caches )
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Memory Hierarchy (3/4) Processor Size of memory at each level Increasing Distance from Proc., Decreasing cost / MB Level 1 Level 2 Level n Level 3 . . . Higher Lower Levels in memory hierarchy
Image of page 10
Memory Hierarchy (4/4) If level is closer to Processor, it must be: smaller faster subset of all higher levels (contains most recently used data) contain at least all the data in all lower levels Lowest Level (usually disk) contains all available data
Image of page 11

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Analogy: Library You’re writing a term paper (Processor) at a table in Evans Evans Library is equivalent to disk essentially limitless capacity
Image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern