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【速搜问答】小型计算机系统接口是什么

问答 admin 1个月前 (01-16) 34次浏览 已收录 0个评论

汉英对照:
Chinese-English Translation:

小型计算机系统接口(SCSI)是一种用于计算机及其周边设备之间(硬盘、软驱、光驱、打印机、扫描仪等)系统级接口的独立处理器标准。

Small computer system interface (SCSI) is an independent processor standard used for system level interface between computer and its peripheral devices (hard disk, floppy drive, optical drive, printer, scanner, etc.).

小型计算机系统接口(SCSI,Small Computer System Interface)是一种用于计算机及其周边设备之间(硬盘、软驱、光驱、打印机、扫描仪等)系统级接口的独立处理器标准。SCSI 标准定义命令、通信协议以及实体的电气特性(换成 OSI 的说法,就是占据物理层、链接层、套接层、应用层),最大部分的应用是在存储设备上(例如硬盘、磁带机);但,其实 SCSI 可以连接的设备包括有扫描仪、光学设备(像 CD、DVD)、打印机……等等,SCSI 命令中有条列出支持的设备 SCSI 周边设备。理论上,SCSI 不可能连接所有的设备,所以有“1Fh – unknown or no device type”这个参数存在。

Small computer system interface (SCSI) is an independent processor standard used for system level interface between computer and its peripheral devices (hard disk, floppy drive, optical drive, printer, scanner, etc.). The SCSI standard defines commands, communication protocols, and electrical characteristics of entities (in other words, it occupies the physical layer, link layer, socket layer, and application layer). The largest part of applications are on storage devices (such as hard disks and tape drives). However, the devices that SCSI can connect include scanners, optical devices (such as CDs and DVDs), printers, etc And so on, the SCSI command has a list of supported devices, SCSI peripherals. Theoretically, it is impossible for SCSI to connect all devices, so the parameter “1fh – unknown or no device type” exists.

特点

characteristic

●SCSI 接口是一个通用接口,在 SCSI 母线上可以连接主机适配器和八个 SCSI 外设控制器,外设可以包括磁盘、磁带、CD-ROM、可擦写光盘驱动器、打印机、扫描仪和通讯设备等。

The SCSI interface is a general interface. The host adapter and eight SCSI peripheral controllers can be connected on the SCSI bus. The peripheral devices can include disk, tape, CD-ROM, erasable CD-ROM drive, printer, scanner and communication equipment.

●SCSI 是个多任务接口,设有母线仲裁功能。挂在一个 SCSI 母线上的多个外设可以同时工作。SCSI 上的设备平等占有总线。

SCSI is a multi task interface with bus arbitration function. Multiple peripherals attached to a SCSI bus can work at the same time. The devices on SCSI share the bus equally.

●SCSI 接口可以同步或异步传输数据,同步传输速率可以达到 10MB/s,异步传输速率可以达到 1.5MB/s。

The SCSI interface can transmit data synchronously or asynchronously. The synchronous transmission rate can reach 10MB / s and the asynchronous transmission rate can reach 1.5mb/s.

●SCSI 接口接到外置设备时.它的连接电缆可以长达 6m。

When the SCSI interface is connected to an external device, its connecting cable can be as long as 6m.

历史

history

最初的 SCSI 标准的最大同步传输速率为 5MB/s(SCSI-1,又名 Narrow

The original SCSI standard had a maximum synchronous transfer rate of 5MB / S (scsi-1, also known as narrow)

1995 年左右出现了第三代 SCSI,但没有统一标准:

The third generation of SCSI appeared around 1995, but there is no unified standard

1. 最大同步传输速度达到 20MB/s 的 Ultra SCSI(又称为 Fast-20 SCSI,时钟频率为 20MHz);

1. Ultra SCSI (also known as FAST-20 SCSI, clock frequency is 20MHz) with maximum synchronous transmission speed of 20MB / s;

2.最大同步传输速度达到 40MB/s 的 Ultra Wide SCSI(同 1);

2. Ultra wide SCSI (same as 1) with maximum synchronous transmission speed of 40MB / s;

3.最大同步传输速度达到 40MB/s 的 Ultra2 SCSI(又称为 Fast-40 SCSI,时钟频率为 40MHz,1997 年)。

3. Ultra2 SCSI (also known as fast-40 SCSI, clock frequency 40MHz, 1997) with maximum synchronous transmission speed of 40MB / s.

稍后,又出现了一些更新的 SCSI 标准:

Later, there are some updated SCSI standards:

1. 最大同步传输速度达到 80MB/s 的 Ultra2 Wide SCSI(时钟频率为 40MHz);

1. Ultra2 wide SCSI (clock frequency 40MHz) with maximum synchronous transmission speed of 80mb / s;

2.最大同步传输速度达到 160MB/s 的 Ultra 3 SCSI(又名 Ultra-160 或者 Fast-80 Wide SCSI,时钟频率为 40MHz 加双倍数据速率,1999 年);

2. Ultra 3 SCSI (also known as ultra-160 or fast-80 wide SCSI, clock frequency 40MHz plus double data rate, 1999) with a maximum synchronous transmission speed of 160MB / s;

3.最大同步传输速度达到 320MB/s 的 Ultra 320 SCSI(又名 Ultra 4 SCSI,时钟频率为 80MHz 加双倍数据速率,2002 年);

3. Ultra 320 SCSI with maximum synchronous transmission speed of 320mb / S (also known as ultra 4 SCSI, clock frequency of 80MHz plus double data rate, 2002);

这种接口是一种便于系统集成、降低成本和提高效率的接口标准,越来越多的设备将使用 SCSI 接口标准,因此,带 SCSI 接口的硬盘和 SCSI 光盘驱动器也很多,但由于成本问题,主要用于中高端服务器与工作站上。

This kind of interface is a kind of interface standard which is convenient for system integration, cost reduction and efficiency improvement. More and more devices will use SCSI interface standard. Therefore, there are many hard disks and SCSI optical drives with SCSI interface. However, due to the cost problem, they are mainly used in high-end servers and workstations.

类型

type

SCSI-1

SCSI-1

SCSI-1 是最原始的版本,异步传输的频率为 3MB/S,同步传输的频率为 5MB/s。虽然几乎被淘汰了,但还会使用在一些扫描仪和内部 ZIP 驱动器中,采用的是 25 针接口。也就是说,若是将 SCSI-1 设备联接到你的 SCSI 卡,必须要有一个内部的 25 针对 50 针的接口电缆;若是用外部设备时,就不能采用内部接口中的任何一个(即此时的内部接口均不可以使用)。

Scsi-1 is the most original version, asynchronous transmission frequency is 3MB / s, synchronous transmission frequency is 5MB / s. Although almost eliminated, it will still be used in some scanners and internal zip drives, using a 25 pin interface. In other words, if you connect a scsi-1 device to your SCSI card, you must have an internal 25 to 50 pin interface cable; if you use an external device, you can’t use any of the internal interfaces (that is, the internal interfaces can’t be used at this time).

SCSI-2

SCSI-2

早期的 SCSI-2,称为 FastSCSI,通过提高同步传输的频率使据传输速率从原有的 5MB/s 提高为 10MB/s,支持 8 位并行数据传输,可连 7 个外设。后来出现的 WideSCSI,支持 16 位并行数据传输,数据传输率也提高到了 20MB/s,可连 16 个外设。此版本的 SCSI 使用一个 50 针的接口,主要用于扫描仪、CD-ROM 驱动器及老式硬盘中。

The early SCSI-2, called fastscsi, increased the data transmission rate from 5MB / s to 10MB / s by increasing the frequency of synchronous transmission. It supports 8-bit parallel data transmission and can connect 7 peripherals. Later, widescsi, which supports 16 bit parallel data transmission, also increases the data transmission rate to 20MB / s, and can connect 16 peripherals. This version of SCSI uses a 50 pin interface for scanners, CD-ROM drives, and older hard drives.

SCSI-3

SCSI-3

1995 年,诞生了更为高速的 SCSI-3,称为 UltraSCSI,数据传输率也达到了 20MB/s。它将同步传输钟频率提高到 20MB/s,提高了数据传输率的技术。若使用 16 位传输的 Wide 模式,数据传输率更可以提高至 40MB/s。此版本的 SCSI 使用一个 68 针的接口,主要应用在硬盘上。SCSI-3 的典型特点是将总线频率大大地提高,并降低信号的干扰,以此来增强其稳定性。

In 1995, a higher speed SCSI-3, called ultrascsi, was born, and the data transmission rate reached 20MB / s. It increases the frequency of synchronous transmission clock to 20MB / s and improves the data transmission rate. If the 16 bit wide mode is used, the data transmission rate can be increased to 40MB / s. This version of SCSI uses a 68 pin interface, which is mainly used on hard disks. The typical feature of SCSI-3 is to increase the bus frequency greatly and reduce the signal interference, so as to enhance its stability.

SCSI-3 有很多型号,Ultra(fast-20)的传输频率 20MHz,数据频宽 8 位,传输率 20MBps

There are many models of SCSI-3. The transmission frequency of ultra (FAST-20) is 20MHz, the data bandwidth is 8 bits, and the transmission rate is 20MBps

Ultra wide 的传输频率 20MHz,数据频宽 16 位,传输率 40MBps

The transmission frequency of ultra wide is 20MHz, the data bandwidth is 16 bits, and the transmission rate is 40mbps

Ultra 2 的传输频率 80MHz,数据频宽 16 位,传输率 80MBps

The transmission frequency of ultra 2 is 80MHz, the data bandwidth is 16 bits, and the transmission rate is 80mbps

Ultra 160 的传输频率 80MHz,数据频宽 16 位,传输率 160MBps

The transmission frequency of ultra 160 is 80MHz, the data bandwidth is 16 bits, and the transmission rate is 160mbps

Ultra 320 的传输频率 80MHz,数据频宽 16 位,传输率 320MBps

The transmission frequency of ultra 320 is 80MHz, the data bandwidth is 16 bits, and the transmission rate is 320mbps

Ultra 640 的传输频率 160MHz,数据频宽 16 位,传输率 640MBps

The transmission frequency of ultra 640 is 160MHz, the data bandwidth is 16 bits, and the transmission rate is 640mbps

区别

difference

除了 SCSI,IDE 也是一种极为常用的接口。从使用简便的角度来看,IDE 更加适合普通用户,再加上个人电脑用户不但需要配置的外设不多,而且对速度要求也不高,因此选用 IDE 接口更合适些。此外,IDE 还具有性能价格比高、适用面广等特点。而 SCSI 接口尽管具有很多无与伦比的特点,但不论从哪个角度看,该接口及其使用该接口的外设售价过于昂贵,一般用户实在无法承受,这也就决定了它的实际使用范围的局限性。

In addition to SCSI, IDE is also a very common interface. From the point of view of ease of use, IDE is more suitable for ordinary users. In addition, personal computer users not only need to configure few peripherals, but also have low speed requirements, so it is more appropriate to choose IDE interface. In addition, IDE has the characteristics of high performance price ratio and wide application. Although the SCSI interface has many incomparable characteristics, no matter from which point of view, the price of the interface and the peripherals using it is too expensive for ordinary users, which determines the limitation of its practical application.

1.IDE 的工作方式需要 CPU 的全程参与,CPU 读写数据的时候不能再进行其他操作,这种情况在 Windows 95/NT 的多任务操作系统中,自然就会导致系统反应的大大减慢。而 SCSI 接口,则完全通过独立的高速的 SCSI 卡来控制数据的读写操作,CPU 就不必浪费时间进行等待,显然可以提高系统的整体性能。不过,IDE 接口为改善这个问题也做了很大改进,已经可以使用 DMA 模式而非 PIO 模式来读写,数据的交换由 DMA 通道负责,对 CPU 的占用可大大减小。尽管如此,比较 SCSI 和 IDE 在 CPU 的占用率,还是可以发现 SCSI 仍具有相当的优势。

1. The working mode of IDE requires the full participation of CPU. When the CPU reads and writes data, it can’t do other operations. In the multitasking operating system of Windows 95 / NT, this situation will naturally slow down the system reaction. The SCSI interface controls the read and write operation of data completely through the independent high-speed SCSI card, so the CPU does not have to waste time waiting, which can obviously improve the overall performance of the system. However, the IDE interface has also made great improvements to improve this problem. It can use DMA mode instead of PIO mode to read and write. The DMA channel is responsible for data exchange, and the CPU occupation can be greatly reduced. However, comparing the CPU utilization of SCSI and IDE, we can find that SCSI still has considerable advantages.

2.SCSI 的扩充性比 IDE 大,一般每个 IDE 系统可有 2 个 IDE 通道,总共连 4 个 IDE 设备,而 SCSI 接口可连接 7—15 个设备,比 IDE 要多很多,而且连接的电缆也远长于 IDE。

2. The expansibility of SCSI is greater than that of IDE. Generally, each ide system can have two IDE channels, connecting a total of four IDE devices. The SCSI interface can connect 7-15 devices, which is much more than IDE, and the connecting cables are much longer than ide.

3.虽然 SCSI 设备价格高些,与 IDE 相比,SCSI 的性能更稳定、耐用,可靠性也更好。

3. Although the price of SCSI device is higher, compared with IDE, the performance of SCSI is more stable, durable and reliable.

优点

advantage

1.SCSI 可支持多个设备,SCSI-2(FastSCSI)最多可接 7 个 SCSI 设备,WideSCSI-2 以上可接 15 个 SCSI 设备。也就是说,所有的设备只需占用一个 IRQ,同时 SCSI 还支持相当广的设备,如 CD-ROM、DVD、CDR、硬盘、磁带机、扫描仪等。

1. SCSI can support multiple devices, SCSI-2 (fastscsi) can connect up to 7 SCSI devices, and widescsi-2 can connect up to 15 SCSI devices. In other words, all devices only need one IRQ. At the same time, SCSI also supports a wide range of devices, such as CD-ROM, DVD, CDR, hard disk, tape drive, scanner, etc.

2.SCSI 还允许在对一个设备传输数据的同时,另一个设备对其进行数据查找。这就可以在多任务操作系统如 Linux、WindowsNT 中获得更高的性能。

2. SCSI also allows another device to look up data while transmitting data to one device. This can achieve higher performance in multitasking operating systems such as Linux and windows NT.

3.SCSI 占用 CPU 极低,确实在多任务系统中占有着明显的优势。由于 SCSI 卡本身带有 CPU,可处理一切 SCSI 设备的事务,在工作时主机 CPU 只要向 SCSI 卡发出工作指令,SCSI 卡就会自己进行工作,工作结束后返回工作结果给 CPU,在整个过程中,CPU 均可以进行自身工作。

3. SCSI occupies a very low CPU, and it really has an obvious advantage in multitasking system. Since the SCSI card itself has CPU, it can handle all the transactions of SCSI devices. When the host CPU sends work instructions to the SCSI card, the SCSI card will work by itself. After the work, it will return the work results to the CPU. In the whole process, the CPU can work by itself.

4.SCSI 设备还具有智能化,SCSI 卡自己可对 CPU 指令进行排队,这样就提高了工作效率。在多任务时硬盘会在当前磁头位置,将邻近的任务先完成,再逐一进行处理。

4. The SCSI device is also intelligent. The SCSI card can queue the CPU instructions by itself, which improves the work efficiency. When multitasking, the hard disk will be in the current head position, and the adjacent tasks will be completed first, and then processed one by one.

5.最快的 SCSI 总线有 160MB/s 的带宽,这要求使用一个 64 位的 66MHz 的 PCI 插槽,因此在 PCI-X 总线标准中所能达到的最大速度为 80MB/s,若配合 10,000rpm 或 15,000rpm 转速的专用硬盘使用将带来明显的性能提升。

5. The fastest SCSI bus has 160MB / s bandwidth, which requires a 64 bit 66MHz PCI slot. Therefore, the maximum speed that can be achieved in PCI-X bus standard is 80mb / s. if it is used with special hard disk with 10000rpm or 15000rpm speed, it will bring obvious performance improvement.

终结器

Terminator

SCSI 链的最后一个 SCSI 设备要用终结器,中间设备是不需要终结器的。一旦中间设备使用了终结器,那么 SCSI 卡就无法找到以后的 SCSI 设备了。而如果最后一个设备没用终结器,SCSI 也是无法正常工作的。终结器是由电阻组成的,位于 SCSI 总线的末端,用来减小相互影响的信号,维持 SCSI 链上的电压恒定。

The last SCSI device in the SCSI chain needs a terminator, and the intermediate device does not need a terminator. Once the terminator is used by the intermediate device, the SCSI card cannot find the future SCSI device. If the last device doesn’t use the terminator, SCSI will not work properly. The terminator is composed of resistors, which are located at the end of the SCSI bus. It is used to reduce the mutual influence signals and maintain the constant voltage on the SCSI chain.

绝大部分 SCSI 设备是内置终结器,并用一跳线来控制 ON/OFF。SCSI 设备智能化程度很高,能自动控制终结器 ON/OFF,如一块硬盘和一个 CD-ROM 相连,无论硬盘的终结器 ON 或 OFF,CD-ROM 都能正常使用。而当两块硬盘相连时,情况就变得复杂了,两块 Seagate 的硬盘相连前,一块硬盘终结器必须是 OFF,而当一块 Seagate 的硬盘和一块 Quantum 硬盘相连前,一个硬盘终结器无论 ON 或 OFF,都能正常使用。

Most SCSI devices are built-in terminators and use a jumper to control on / off. SCSI devices are highly intelligent and can automatically control the terminator on / off. For example, if a hard disk is connected to a CD-ROM, the CD-ROM can work normally no matter the terminator is on or off. When two hard disks are connected, the situation becomes more complicated. Before two Seagate hard disks are connected, a hard disk terminator must be off. When a Seagate hard disk is connected with a quantum hard disk, a hard disk terminator can work normally no matter on or off.

ID

ID

系统中的每个 SCSI 设备都必须有自己唯一的 ID(标识号),在 8-bit 总线上,这个号码是 0~7;在 16-bit 总线上,这个号码从 0~15。SCSIAdapter 系统默认 ID 为 7。这个 ID 可由位于设备前端的跳线器来设置。对于硬盘它位于驱动器的前端或后端。

Each SCSI device in the system must have its own unique ID (identification number). On 8-bit bus, the number is 0 ~ 7; on 16 bit bus, the number is 0 ~ 15. The default ID of scsiadapter system is 7. This ID can be set by the jumper at the front of the device. For hard disks, it’s on the front or back of the drive.


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