l21 - Memory Design Memory can be built in different...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Memory Design Memory can be built in different ways... Dynamic (DRAM): leaky, has to be refreshed periodically Static (SRAM) Memory access latency: DRAM: 50-70ns, larger memory size (can t more in a given area) SRAM: 3-10ns, smaller memory size CPU clock cycle time: 0.5-2ns Processor-Memory Gap Current trends: Component Capacity Speed Transistors/logic 1.4x each year 2x in 3 years DRAM 4x in 3 years 1.4x in 10 years Disk 4x in 3 years 1.4x in 10 years The gap between processor speed and memory speed is growing. CPI Equation Suppose: 60ns DRAM, 500MHz CPU. Instruction mix: ALU: 50%, load/store: 30%, branch: 20% Assume branch delay slots are all lled with nop s. MIPS CPI: . 5 1 + 0 . 2 2 + 0 . 3 30 9 . 9 ! Problem: memory is too slow. Speeding Up Memory Access Basic idea: Build a small, fast memory ( cache ) Use to store frequently accessed blocks of memory When it lls up, discard some blocks and replace them with others Works well if we are reusing data blocks Examples: incrementing a variable, loops, function calls, etc. Locality Principles Temporal Locality the location of a memory reference is likely to be...
View Full Document

This note was uploaded on 06/25/2008 for the course ECE 3140 taught by Professor Mckee/long during the Spring '07 term at Cornell University (Engineering School).

Page1 / 19

l21 - Memory Design Memory can be built in different...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online