2018-2019-1 20165325 summary of the fifth week of Information Security System Design Basics

2018-2019-1 20165325 summary of the fifth week of Information Security System Design 1. Storage Technology

Memory can be divided into volatile memory and non-volatile memory,Volatile memoryWhen the computer is shut down or accidentally shut down, the data in the computer will be lost, just like the memory.Non-volatile memoryIn this case, data will not be lost, such as external storage such as hard disk.

(1) volatile memory

SRAMAndDRAMAll are volatile memory. According to different storage information, random memory is divided into static random memory (static RAM, SRAM) and dynamic random memory (Dynamic RAM, Dram ).

Static storage unit (SRAM ):

● Storage principle: data is stored by triggers.

● Advantages: high speed, simple use, no need to refresh, low static power consumption; commonly used as cache

● Disadvantages: large number of components, low integration, and High Power Consumption

Dynamic Storage Unit (Dram ):

● Storage principle: the principle that the gate capacitor of MOS can store the charge needs to be refreshed (early stage: Three-tube basic unit; now: single-tube Basic Unit)

● Advantage: the integration level is much higher than that of SRAM, the power consumption is low, and the price is low.

● Disadvantages: The peripheral circuit is complicated because of the need to be refreshed. Refresh also slows down the access speed compared to dram. in computer systems, SRAM is often used as the primary memory.

(2) non-volatile memory (ROM)/read-only storage

Programmable Rom (PROM): can only be programmed once.

Erasable Programmable Rom (EPROM): When ultraviolet light is exposed to a window, the EPROM is cleared to 0 and erased and reprogrammed 1000 times.

Electronic erasable Rom (EEPROM): it does not require a physically independent programming device, so it can be programmed directly on the printed circuit card, and the number of programming times is 10 ^ 5.

Flash Memory: Based on EEPROM, it provides fast and persistent non-volatile storage for a large number of electronic devices.

2. Disks

(1) disk structure

The head is located on the surface of each disk. The head is connected to the arm. The arm can move all the heads together as a whole, the disk surface is logically divided into a circular track, and the track is further divided into sectors. Cylinder is a collection of tracks at the same arm position. Each disk drive has thousands of concentric cylinder, and each track may contain hundreds of sectors. The storage capacity of common disk drives is calculated by GB.

(2) disk capacity: the maximum number of BITs that can be recorded on a disk is called its maximum capacity/capacity.

The following are the deciding factors:

(A) record density: the number of digits that can be placed in the segment of the track 1 inch.

(B) Track density: the number of tracks that can exist within a 1 inch radius starting from the disc center.

(C) surface density: the product of record density and track density.

Formula:

Disk capacity = Bytes/sector * Average disk space/track * channels/surface * surface/disk space * disk space/Disk

3. Bus

The computer bus can be divided:

• Data Bus

• Control bus

• Address Bus

Categories by CPU internal and external:

• System Bus

• Storage Bus

• I/O bus

4. read/write transactions

(1) read: The Master memory is stored in the CPU

(2) Write: CPU to primary storage

5. locality of Program Data Reference

(1) read: The Master memory is stored in the CPU

(2) Write: CPU to primary storage

6. the central idea of the storage hierarchy: each layer of storage devices is a "cache" of the next layer"

For each K, a faster and smaller storage device located on the K layer serves as the cache for a slower and larger storage device located on the K + 1 layer. That is, each layer in the hierarchy caches data objects from the lower layer. Data is always replicated back and forth between the K layer and the k + 1 layer based on the block size as the transfer unit (transfer unit.

Example:

Resolution: each layer of the Memory Hierarchy caches data from the lower layer. Cache memory is segmented, and data is always transmitted between each layer based on blocks. The size of blocks is only the same between the two layers.

2018-2019-1 20165325 summary of the fifth week of Information Security System Design Basics