20135234 Ma Qiyang-—— Information Security system design basics Seventh Week study summary

Sixth chapter Memory Hierarchy

A memory system is a hierarchical structure of storage devices with different capacity, cost, and access times.

The CPU registers hold the most commonly used data.

Small, fast cache memory close to the CPU as part of the cache area of data and instructions stored in relatively slow primary memory (memory).

Main memory temporarily stores data stored on a large, slow disk, which is often used as a cache area for data stored on disks or tapes of other machines connected over the network.

6.1 Storage Technology

6.1.1 Random access memory

Random access memory (RAM) is divided into: static RAM (SRAM) and dynamic RAM (DRAM)

SRAM is used as a cache memory, either on the CPU chip or under the chip.

DRAM is used as a frame buffer for primary and graphical systems.

　　　　

1. Static RAM

SRAM stores each bit in a bistable memory unit

That is, as long as there is electricity, it will keep its value forever. Even if there is interference

　　　　

2. Dynamic RAM

DRAM stores each bit as a charge to a capacitor

The DRAM memory unit is very sensitive to interference, and when the voltage of the capacitor is disturbed, it will never recover again.

3. The traditional DRAM

The units (BITS) in a DRAM chip are divided into D-units, each of which consists of a W DRAM unit. A DXW dram stores the DW bit information in total. The cells are organized into a rectangular array of R row C columns, Rc=d here. Each of the cells is tangible such as (I,J) address, I is the row, J represents the column.

4. Memory Module

The DRAM chip is packaged in a memory module and is found in the expansion slots of the motherboard. Common packaging includes a 168-pin dual-inline memory module that transmits data to the storage controller and data from the storage controller in 64-bit chunks, and includes 72 pin single-line memory modules that transmit data in 32-bit blocks.

5. Enhanced DRAM

Improvements to DRAM:

(1) Fast-page mode dram

(2) Extended data output dram

(3) Synchronous DRAM

(4) Double data rate synchronous DRAM

(5) Rambusdram (RDRAM)

(6) Video-on-screen dram

6. Non-volatile memory

If breakpoints, DRAM and SRAM lose information, which is volatile.

Conversely, after a power outage, the information is still stored, which is non-volatile memory.

7. Accessing main memory

The data flows back and forth between processing and DRAM main memory through a shared electronic circuit called a bus.

Each time the data transfer between the CPU and main memory is done through a series of steps called Bus things.

Read things transfer data from main memory to the CPU.

Writes things from the CPU to the main memory.

6.1.2 Disk storage

1. Disk Construction

(1) The disk consists of a disc surface, each face has two sides or a surface, the surface covering the recording material.

The center of the platter has a rotating spindle that rotates the disc at a fixed rotational rate, usually 5400~15000 rpm.

(2) Each surface is made up of a set of concentric circles that become tracks. Each track is divided into a set of sectors.

Each sector contains an equal number of bits of data encoded in magnetic materials on the sector.

The sectors are separated by a few gaps in which data bits are not stored. Interstitial storage used to identify the formatting bits of a mountain

(3) The disk is made up of one or more stacked platters, which are placed in a sealed package.

The entire device is often referred to as a disk drive, referred to as disk.

Cylinder: The set of tracks that are equal to the center of the spindle on all disc surfaces.

2. Disk capacity

Recording density: The number of digits that can be placed in the segment of each inch of the track

Track density: The number of tracks that can be in an inch from the center of the disc

Surface density: The product of recording density and track density

Disk Capacity: (bytes/sector) x (average sector/track) x (number of tracks/surface) x (number of surfaces/platters) x (number of discs/disk)

3. Disk operation

The disk uses a read/write header to read and write the bits stored on the magnetic surface, while the read-write head is connected to one end of the transmission arm.

By moving the drive arm back and forth along the radius axis, the driver can position the read/write head on any track on the disc, a mechanical motion called a seek path.

The sector access time is divided into three parts:

(1) Seek time:

(2) Rotation time:

Tmax rotation = (1/rpm) x (60secs/1min)

Average rotation time tavg rotation is Tmax rotation half

(3) Delivery time:

Tavg transfer = (1/rpm) x (1/(average sector number/track) x (60secs/1min)

4. Logical Disk Block

5. Connecting to I/O devices

6. Accessing the disk

6.1.3 Solid State Disk

6.1.4 Storage Technology Trends

　　　　

　　　　　　

　　　　　　

　　　　　　

　　　　

　　　　　　

20135234 Ma Qiyang-—— Information Security system design basics Seventh Week study summary