Word Assembly from Narrow Chips t A d d r e s s R / W C S C S C S R / W R / W . . . R / W A d d r e s s A d d r e s s A d d r e s s D a t a D a t a D a t a s s s p ´ s P chips expand word size from s bits to p x s bits.

CS501 Advanced Computer Architecture Lecture 38 Dr.Noor Muhammad Sheikh

Review

Cost of pins on a chip encourages narrow words for high capacity memory. Adding a data pin to a chip increases the number of bits it can store.

Read only Memory

Memory Hierarchy

Cache Memory

Memory Module

More chip capacity can be accommodated with fewer pins by increasing the address size rather than the word size.

Example Consider 4 chips with s=4, word size = 4bits Data bus = 16bits, o/p = 16 bits With SRAM chip no refresh required. With DRAM chip, RAS and CAS coordination.

Increasing the Number of Words by a Factor of 2k

Figure 7.19 (jordan)

Chip Matrix Using Two Chip Selects address m+q+k Horizontal decoder k m R/W cs1 cs2 address q A R/W Data Vertical decoder s One of 2m+q+k S-bit words

A Memory Module and Its Interface Address k+m Address register k m Chip/board selection Module select Memory boards and/or chip Control Signal generator Read Write Ready w Data register Data w

Dynamic RAM Module with Refresh Control k + m R a W i y D w / 2 f h n q G g C p b x B S

Two Kinds of Memory Module Organizations j k M o d u l e s b m A r + = - i t a c 1 2 – ( ) C n v w g h . .

A 2-D CMOS ROM Chip + v Address Row decoder CS 1 1

The cache mapping function CPU Word cache Main Memory Block address Mapping function

Cache operation are transport to the running program. The program issues effective addresses and read or write requests, and these requests are satisfied by memory Whether it is the cache or main memory that satisfies the request is unknown to the program The cache blocks are sometimes referred to as cache lines

Continued Cache mapping is responsible for all the cache operations. Cache is implemented in hardware to achieve high speed operation.

Mapping function determines the following: Placement strategies Replacement strategies Read and write policies