Memory system
Computer hardware systems
Memory effect
- Means for storing computer programs and data, Von Neumam structure is an important component of a computer, the computer center.
- Stored program computer to GM
- Features of the program and the data
source, assembler, machine language program
various types of data
in common: binary data
The basic requirements of the storage medium
- To have two stable states to represent a binary "0" and "1"
- Easy to identify
- Two states can be easily converted
- Several common storage
of magnetic particles, semiconductor (level / capacitance), a light
Early memory
- Mercury delay line
memory works: wave - Core memory
The semiconductor memory
- Storage principle
MOS transistor parasitic capacitance (DRAM)
flip-flop (SRAM) - Access mechanism
random access - Classification of
a ROM, the RAM
the SRAM, a DRAM
Modern computer storage systems
Register register
cache cache
main memory main memory
disk disk
cassette tape
disc compact disc
Memory system design goals
- Storage speed as quickly as possible
should be able to basically meet the requirements CPU access to data - Storage space as large as possible
to meet the program requirements for storage space - As low unit cost (price / bit)
the user is able to withstand a range of - High reliability
Why memory system design
A single memory can not meet these needs
Microelectronics Technology trends
| capacity | speed | |
|---|---|---|
| Logic circuit | 2 times / 3 years | 2 times / 3 years |
| DRAM | 4 times / 3 years | 2 times / 10 years |
| Disk | 4 times / 3 years | 2 times / 10 years |
DRAM
| year | size | cycle time |
|---|---|---|
| 1980 | 64KB | 250ns |
| 1983 | 256KB | 220ns |
| 1986 | 1MB | 190ns |
| 1989 | 4nb | 165ns |
| 1992 | 16MB | 145ns |
| 1995 | 64MB | 120ns |
Memory design goals
- Target
high-capacity, high speed, low cost, high reliability - Currently reality
a mass storage device is slow
block memory capacity small - How to achieve our goal
level memory technologies
using parallel
Level memory system
- Speed
static high speed memory
provided small capacity buffer cache - Large-capacity
dynamic memory affordable, moderate speed
can be used as a main memory - Low-cost
and low price memory disk
as an auxiliary storage, staging, CPU frequency is not high memory access data and programs
as a carrier of virtual memory
Running principle of locality
Locality principle embodied in the running:
in short period of time, recently accessed programs and data likely to be accessed again
in space, these programs and data to be accessed often concentrated in a storage area
on the access order , more likely than the order of execution of instructions performed by transfer (approximately 5: 1)
reasonable to assign different programs and data in a storage medium
Principle between the level should be met
- Consistency principle: the same information at different levels of memory should maintain the same value
- Principle comprising: information must be contained in the inner layer of the outer layer in the memory, but not vice versa.
The principle of locality using program
At the lowest possible price to provide large storage space
with the fastest technology to achieve high-speed access to storage space
