All types of DRAM and their function.ppt

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1. Dynamic Random Access Memory
(DRAM)
CS 350 Computer Organization
Spring 2004
Aaron Bowman
Scott Jones
Darrell Hall

2. DYNAMIC RANDOM ACCESS
MEMORY (DRAM)
•Simple DRAM
•Fast Page Mode (FPM) DRAM
•Extended Data Out (EDO) DRAM
•Burst Extended Data Out (BEDO) DRAM
•Synchronous DRAM (SDRAM)
•Rambus DRAM (RDRAM)
•Double Data Rate (DDR) DRAM

3. Simple DRAM
 Memory system directly connected to the CPU and was
the basic architecture that was most commonly used by
system designers on early microcomputer systems
 Simplest system to design and also the least expensive
 Preferred type for systems with a processor that
operates at speeds lower than 16 MHz
 In the late 1980s processors began to operate at
speeds faster than that so a new architecture was
necessary.

4. Fast Page Mode (FPM) DRAM
 Continually accesses memory from the same row of
RAM without having to specify the row each time
 Burst cycle timing as fast as 6-3-3-3
 Not only does this increase the access speed, but it
also lowers power requirements.
 Rarely used because it is slower than newer memory
types

5. Extended Data Out (EDO) DRAM
 Often called Hyper Page Mode DRAM
 Modified timing circuits that allow it to begin one
memory access before the previous one has finished
 Burst cycle timing as fast as 6-2-2-2
 With no price difference and the speed gained using
EDO DRAM, there was no reason to choose FPM DRAM
over EDO DRAM.

6. BEDO DRAM
•Advantages over
EDO
•Improved Cycle
time with address
counter on chip
•Optimized use of
four set data burst
•Disadvantage
•Not Synchronized with
CPU
•Not keep up with
buses faster the 66
MHz
•Built on asynchronous
bus compared to
SDRAM

7. SDRAM
•First type of DRAM to run synchronous
with the CPU
•This allowed SDRAM to run at faster
speeds
•Comes in SIMMs and DIMMs
•SIMMs need two modules
•DIMMs need one module

8. RDRAM
•RDRAM is short for Rambus DRAM.
•Created by the Rambus company.
•RDRAM can transfer data up to 800 MHz.

9. •A single RDRAM is able of providing up to 1.6
GB per second data transmission even
though it has a low pin count.
•Turnaround latency is comparatively faster,
at 12 to 23 nanoseconds.
•RDRAM equipped systems are more efficient
and achieve lower latency over SDRAM.
RDRAM

10. DDR-SDRAM
•DDR-SDRAM is short for Double Data Rate-
Synchronous DRAM.
•SDRAM II and DDRAM are other names for
DDR-SDRAM.
•Uses both the raising and falling edge of the
clock signal for the transfer of data.

11. •First generations peaked at 333 to 400 MHz
with memory up to 512 Mbits.
•Second-generations DDR II is capable of
400 MHz.
•Third generation DDRs will offer even
higher data rates due out late 2004 or early
2005.
DDR-SDRAM