Fall 2006

Lillevik 333f06-l14 1University of Portland School of Engineering

EE 333

Computer OrganizationLecture 14

Memory hierarchy, locality

Memory design

Fall 2006

Lillevik 333f06-l14 2University of Portland School of Engineering

EE 333

Correction: machine instructionInstruction Type Op rs rt rd immed

/adrfunct Machine

(hex)add $0, $0, $1 R 0x1 0 1 0 na 0x0 0x1400

andi $0, $1, 10f I 0xc 0 1 na 0x10f na 0xa90f

sll $0, $1 I 0x2 0 1 na na na 0x2400

lw $0, 323 ($1) I 0x4 1 0 na 0x323 na 0x4b23

beq $0, $1, 17a I 0x6 0 1 na 0x17a na 0x657a

j a64 J 0x7 na na na 0xa64 na 0x7a64

Correction

Fall 2006

Lillevik 333f06-l14 3University of Portland School of Engineering

EE 333

Any questions on Project 4?

• Two, 16-bit registers ($0, $1)

• Two read ports

• One write port

• Equal output

• Due: Nov. 3

Fall 2006

Lillevik 333f06-l14 4University of Portland School of Engineering

EE 333

Major computer components

Five classic computer components

Fall 2006

Lillevik 333f06-l14 5University of Portland School of Engineering

EE 333

Computer components

• Input: receives information from external world

• Output: transmits information to external world

• Memory: holds programs and data

• Data path: physical route that carries info

• Control: coordinates overall flow of info

Fall 2006

Lillevik 333f06-l14 6University of Portland School of Engineering

EE 333

Memory design goals

• Unlimited memory size– No upper bound on memory addresses– Not practical or possible: cost, implementation

• Infinite memory bandwidth– Zero latency memory accesses– Not practical or possible: cost, laws of physics

• Memory hierarchy can approximate goals

Fall 2006

Lillevik 333f06-l14 7University of Portland School of Engineering

EE 333

Memory hierarchy

Memory closest to CPU is most expensive (fast) but smallest

On-chip

On-board

In-system

Fall 2006

Lillevik 333f06-l14 8University of Portland School of Engineering

EE 333

Main and cache memory

Each memory may contain a subset of the others

Processor

Data are transferred

Cache

Main

Fall 2006

Lillevik 333f06-l14 9University of Portland School of Engineering

EE 333

Storage hierarchy

Information flows between layers

Less costly Faster

Directly accessed

Indirectly accessed

Fall 2006

Lillevik 333f06-l14 10University of Portland School of Engineering

EE 333

Principle of locality

Programs access a relatively small portion of their address space at any instant of time

• Temporal locality: once memory is accessed, its likely to be accessed again (locality in time)

• Spatial locality: once a memory address is selected, its neighbors are likely to be selected (locality in space)

Fall 2006

Lillevik 333f06-l14 11University of Portland School of Engineering

EE 333

Memory devices

• RAM: random access memory– Random access memory (versus sequential)– Read and write– Usually loose contents with power (volatile)

• ROM: read-only memory– Read only memory– Also random access– Usually non-volatile, or OS protects it

Fall 2006

Lillevik 333f06-l14 12University of Portland School of Engineering

EE 333

• Inputs– Address– Data in (RAM only)– Read/write control (RAM only)– Enable

• Outputs– Data out– Usually tri-state drivers (on & off, pull-ups)

Memory components

A

DQ

E

R/W

Fall 2006

Lillevik 333f06-l14 13University of Portland School of Engineering

EE 333

Tri-state drivers

• You may connect tri-state outputs together

• Must assure only one driver enabled at-a-time

• Common in memory designs, results in MUX function

Fall 2006

Lillevik 333f06-l14 14University of Portland School of Engineering

EE 333

General memory design

A

DQ

E

R/W

A

DQ

E

R/W

In 0

E

1

n

AddressData

R/W

Qout(lower bits)

(upper bits)

decoder

memory

memory

Fall 2006

Lillevik 333f06-l14 15University of Portland School of Engineering

EE 333

Memory design guide

• Bus lower addresses to all devices• Use upper addresses and decoder for device

enables (only one active component)

• Data bus and other control signals sent to all devices

• No read-write signal for ROM• Bus outputs together because they are tri-

stated

Fall 2006

Lillevik 333f06-l14 16University of Portland School of Engineering

EE 333

ROM design: 64 x 8Use 32x8

First ROM

Second ROM

Fall 2006

Lillevik 333f06-l14 17University of Portland School of Engineering

EE 333

ROM 64x8 trace

First ROM selected Second ROM selected Float

ROM file data is the address

Fall 2006

Lillevik 333f06-l14 18University of Portland School of Engineering

EE 333

ROM design: 64 x 16 ?Use 32x8

Fall 2006

Lillevik 333f06-l14 19University of Portland School of Engineering

EE 333

ROM 64x16 trace

First ROMs selected Second ROMs selected Float

Fall 2006

Lillevik 333f06-l14 20University of Portland School of Engineering

EE 333

Memory capacity and components

c00c0n c01

c10c1n c11

c20c2n c21

c30c3n c31

cm0cmn cm1

Greater length (bytes)

Greater width (bits)

m rows, n columns

Fall 2006

Lillevik 333f06-l14 21University of Portland School of Engineering

EE 333

Find the array of components?

Memory Component Length Width4K x 8 2K x 4

16M x 32 1M x 8

4G x 64 500M x16

Fall 2006

Lillevik 333f06-l14 22University of Portland School of Engineering

EE 333

General memory design

A

DQ

E

R/W

A

DQ

E

R/W

In 0

E

1

n

AddressData

R/W

Qout(lower bits)

(upper bits)

decoder

memory

memory

Fall 2006

Lillevik 333f06-l14 23University of Portland School of Engineering

EE 333

RAM design: 16x8Use 16x4

Fall 2006

Lillevik 333f06-l14 24University of Portland School of Engineering

EE 333

RAM 16x8 trace

Writing Reading

Fall 2006

Lillevik 333f06-l14 25University of Portland School of Engineering

EE 333

RAM design: 32x8 ?Use 16x4

Fall 2006

Lillevik 333f06-l14 26University of Portland School of Engineering

EE 333

RAM 32x8 trace

Writing

Reading

Fall 2006

Lillevik 333f06-l14 27University of Portland School of Engineering

EE 333

Fall 2006

Lillevik 333f06-l14 28University of Portland School of Engineering

EE 333

ROM design: 64 x 16 ?Use 32x8