Linux Study Notes (1) -- Understanding linux and hosts

1. CPU. the CPU has the so-called "multiplier" and "external frequency". The external frequency is the speed at which all the system's interface devices operate. The multiplier is the computing speed added when the CPU itself operates! The multiplication of the two is the CPU frequency. However, because the interface device is not so fast, some interface devices need to divide the external frequency into a number before communication. For example, the normal speed of the PCI interface is 33 MHz. Therefore, if the external frequency of your CPU is 133, the speed of the interface device must be divided by 4 to communicate with the system! Generally, the higher the frequency, the faster the CPU computing speed. Taking Intel's PIII frequency 933MHz as an example, the CPU external frequency and frequency doubling: 133 (external frequency) X 7 (Frequency Doubling) MHz RAM frequency: usually the same as the CPU external frequency, for the 133 MHz PCI interface (including network card, sound card and other interfaces) 133/4 = 33 MHz AGP interface: 133/2 = 66 MHz (this is the normal frequency of AGP !) B. another thing to note is that "CPU is classified", which is the i386, i586, and i686 we often see. This is the optimization of CPU of different levels by many programs. 2. graphics card (VGA card) GPU: To avoid CPU troubles caused by a large number of 3D images, therefore, the display card developer inserts a hardware on the display card to process these images, which consumes a lot of CPU computing time. As a result, not only does the image processing speed increase, CPU resources are also used to execute other tasks. Memory is also available on the vgacard. This memory size can affect the screen output resolution and image quality. 3. The PCI adapter uses a hard disk as an example. This SCSI interface is used in addition to the mainstream IDE/SATA interfaces of PCs. Because the SCSI interface is relatively stable, and the device runs fast, it consumes less CPU resources. Currently, the SCSI adapter is the hard disk transmission interface of a general large server host. However, it is enough to use the IDE/SATA interface for personal computers. 4. hardware and hardware device code in Linux Device code IDE Hard Drive/dev/hd [a-d] SCSI hard drive/dev/sd [a-p] CDROM/dev /cdrom floppy disk/dev/fd [0-1] printer/dev/lp [0-2] mouse/dev/mouse tape drive/dev/ht0 (IDE) or/dev/st0 (SCSI interface) network card/dev/ethn (n starts from 0) 5. hard Disk connection and hard disk number are usually produced after 586 there are two interfaces to connect the motherboard (the cable is used to connect the hard disk and the motherboard ), we call this interface an IDE interface, which is also the mainstream hard disk interface (which has been replaced by SATA ). To separate the order of Hard Disk reading, the two interfaces on the motherboard are called the Primary (main) and Secondary (Secondary) IDE interfaces respectively, or IDE1 (Primary) and IDE2 (Secondary ). There are two jacks on each line, that is, a line can be connected to two IDE interfaces (hard disk or optical drive), and you have two lines, so a motherboard is in the default situation, each device can be connected with four IDE interfaces, and the master and slave disks on each cable are differentiated Based On jumpers. IDE \ Jumper Master Slave IDE1 (Primary)/dev/had/dev/hdb IDE2 (Secondary)/dev/hdc/dev/hdd if there is only one hard disk, in addition, if this hard disk is connected to the IDE2 master, the code in Linux is/dev/hdc. 6. Hard Disk partitioning generally consists of the smallest physical unit (sector). When multiple sectors form a concentric circle, they are called cylinder and finally constitute the capacity of the entire hard disk. The hard disk is divided into two areas: the Master Boot Recorder to prevent the information area of the hard disk, and the other is the place where the actual file data is stored. MBR records the boot program and the disk partition table (partition table, the n disk blocks are from the x to the y ), our partition operation is to modify the partition table in the MBR. You can only have one extended partition. The sector at the beginning of each partition has a special block called a super block. One hard disk partition: 7. XWindow directly presses [Ctrl] + [Alt] + [Backspace] on the X screen, you can directly restart X and read the setting file directly. [Ctrl] + [Alt] + [F1] ~ [F6], use the command line to log on to tty1 ~ Tty6 terminal; [Ctrl] + [Alt] + [F7]; GUI desktop. Startx can start the graphic interface from the command line. 8. meaning of different numbers in Linux manual: code indicates content 1 commands that users can operate or execute file 2 common functions (functions) such as the system core callable functions and tools) description of device files with function library 4 5 setting files or formats of certain files 6 games 7 Conventions and Protocols, etc, for example, Linux standard file system, network protocol, ASCII code, and so on 8 System Administrator available management command 9 kernel-Related File whatis = man-f, for more information, see apropos = man-k.