Some expansion cards take up more than one slot space. For example, many graphics cards on the market as of 2010 are dual slot graphics cards, using the second slot as a place to put an active heat sink with a fan. Some cards are 'low-profile' cards, meaning that they are shorter than standard cards and will fit in a lower height computer chassis. An expansion slot refers to any of the slots on a motherboard that can hold an expansion card to expand the computer's functionality, like a video card, network card, or sound card. The expansion card is plugged directly into the expansion port so that the motherboard has direct access to the hardware. Expansion Slots definition What is EXPANSION SLOTS: Connectors inside the computer in which expansion cards are placed so that they tie in directly to the system. How works expansion slots meaning in Dictionary E.

^[1]In computing, an expansion card, also known as an expansion board, adapter card or accessory card, is a printed circuit board that can be inserted into an electrical connector, or expansion slot, on a computer motherboard, backplane or riser card to add functionality to a computer system via the expansion bus.

Expansion cards allow the capacities and interfaces of a computer system to be adjusted to the tasks it will perform. For example, a high-speed multi-channel data acquisition system would be of no use to a personal computer used for bookkeeping, but might be a key part of a system used for industrial process control. Expansion cards can often be installed or removed in the field, allowing a degree of user customization for particular purposes. Some expansion cards take the form of 'daughterboards' that plug into connectors on a supporting system board.

In personal computing, notable expansion buses and expansion card standards include the S-100 bus from 1974 associated with the CP/Moperating system, the 50-pin expansion slots of the original Apple II computer from 1977 (unique to Apple), IBM's Industry Standard Architecture (ISA) introduced with the IBM PC in 1981, Acorn's tube expansion bus on the BBC Micro also from 1981, IBM's patented and proprietary Micro Channel architecture (MCA) from 1987 that never won favour in the clone market, the vastly improved Peripheral Component Interconnect (PCI) that displaced ISA in 1992, and PCI Express from 2003 which abstracts the interconnect into high-speed communication 'lanes' and relegates all other functions into software protocol.

History[edit]

Even vacuum-tube based computers had modular construction, but individual functions for peripheral devices filled a cabinet, not just a printed circuit board. Processor, memory and I/O cards became feasible with the development of integrated circuits. Expansion cards allowed a processor system to be adapted to the needs of the user, allowing variations in the type of devices connected, additions to memory, or optional features to the central processor (such as a floating point unit). Minicomputers, starting with the PDP-8, were made of multiple cards, all powered by and communicating through a passive backplane.

The first commercial microcomputer to feature expansion slots was the Micral N, in 1973. The first company to establish a de facto standard was Altair with the Altair 8800, developed 1974–1975, which later became a multi-manufacturer standard, the S-100 bus. Many of these computers were also passive backplane designs, where all elements of the computer, (processor, memory, and I/O) plugged into a card cage which passively distributed signals and power between the cards.

Proprietary bus implementations for systems such as the Apple II co-existed with multi-manufacturer standards.

IBM PC and descendants[edit]

IBM introduced what would retroactively be called the Industry Standard Architecture (ISA) bus with the IBM PC in 1981. At that time, the technology was called the PC bus. The IBM XT, introduced in 1983, used the same bus (with slight exception). The 8-bit PC and XT bus was extended with the introduction of the IBM AT in 1984. This used a second connector for extending the address and data bus over the XT, but was backward compatible; 8-bit cards were still usable in the AT 16-bit slots. Industry Standard Architecture (ISA) became the designation for the IBM AT bus after other types were developed. Users of the ISA bus had to have in-depth knowledge of the hardware they were adding to properly connect the devices, since memory addresses, I/O port addresses, and DMA channels had to be configured by switches or jumpers on the card to match the settings in driver software.

IBM's MCA bus, developed for the PS/2 in 1987, was a competitor to ISA, also their design, but fell out of favor due to the ISA's industry-wide acceptance and IBM's licensing of MCA. EISA, the 32-bit extended version of ISA championed by Compaq, was used on some PC motherboards until 1997, when Microsoft declared it a 'legacy' subsystem in the PC 97 industry white-paper. Proprietary local buses (q.v. Compaq) and then the VESA Local Bus Standard, were late 1980s expansion buses that were tied but not exclusive to the 80386 and 80486 CPU bus.^[2][3][4] The PC/104 bus is an embedded bus that copies the ISA bus.

Intel launched their PCI bus chipsets along with the P5-based Pentium CPUs in 1993. The PCI bus was introduced in 1991 as a replacement for ISA. The standard (now at version 3.0) is found on PC motherboards to this day. The PCI standard supports bus bridging: as many as ten daisy chained PCI buses have been tested. Cardbus, using the PCMCIA connector, is a PCI format that attaches peripherals to the Host PCI Bus via PCI to PCI Bridge. Cardbus is being supplanted by ExpressCard format.

Intel introduced the AGP bus in 1997 as a dedicated video acceleration solution. AGP devices are logically attached to the PCI bus over a PCI-to-PCI bridge. Though termed a bus, AGP usually supports only a single card at a time (LegacyBIOS support issues). From 2005 PCI-Express has been replacing both PCI and AGP. This standard, approved^{[Like whom?]} in 2004, implements the logical PCI protocol over a serial communication interface. PC/104(-Plus) or Mini PCI are often added for expansion on small form factor boards such as Mini-ITX.

For their 1000 EX and 1000 HX models, Tandy Computer designed the PLUS expansion interface, an adaptation of the XT-bus supporting cards of a smaller form factor. Because it is electrically compatible with the XT bus (a.k.a. 8-bit ISA or XT-ISA), a passive adapter can be made to connect XT cards to a PLUS expansion connector. Another feature of PLUS cards is that they are stackable. Another bus that offered stackable expansion modules was the 'sidecar' bus used by the IBM PCjr. This may have been electrically comparable to the XT bus; it most certainly had some similarities since both essentially exposed the 8088 CPU's address and data buses, with some buffering and latching, the addition of interrupts and DMA provided by Intel add-on chips, and a few system fault detection lines (Power Good, Memory Check, I/O Channel Check). Again, PCjr sidecars are not technically expansion cards, but expansion modules, with the only difference being that the sidecar is an expansion card enclosed in a plastic box (with holes exposing the connectors).

Other families[edit]

Most other computer lines, including those from Apple Inc. (Apple II, Macintosh), Tandy, Commodore, Amiga, and Atari, offered their own expansion buses. The Amiga used Zorro II. Apple used a proprietary system with seven 50-pin-slots for Apple II peripheral cards, then later used the NuBus for its Macintosh series until 1995, when they switched to a PCI Bus. Generally, PCI expansion cards will function on any CPU platform if there is a software driver for that type. PCI video cards and other cards that contain a BIOS are problematic, although video cards conforming to VESA Standards may be used for secondary monitors. DEC Alpha, IBM PowerPC, and NEC MIPS workstations used PCI bus connectors.^[5] Both Zorro II and NuBus were plug and play, requiring no hardware configuration by the user.

Even many video game consoles, such as the Sega Genesis, included expansion buses; at least in the case of the Genesis, the expansion bus was proprietary, and in fact the cartridge slots of many cartridge based consoles (not including the Atari 2600) would qualify as expansion buses, as they exposed both read and write capabilities of the system's internal bus. However, the expansion modules attached to these interfaces, though functionally the same as expansion cards, are not technically expansion cards, due to their physical form.

Other computer buses were used for industrial control, instruments, and scientific systems. Some of these standards were VMEbus, STD Bus, and others.

External expansion buses[edit]

Laptops generally are unable to accept most expansion cards. Several compact expansion standards were developed. The original PC Card expansion card standard is essentially a compact version of the ISA bus. The CardBus expansion card standard is an evolution of the PC card standard to make it into a compact version of the PCI bus. The original ExpressCard standard acts like it is either a USB 2.0 peripheral or a PCI Express 1.x x1 device. ExpressCard 2.0 adds SuperSpeed USB as another type of interface the card can use. Unfortunately, CardBus and ExpressCard are vulnerable to DMA attack unless the laptop has an IOMMU that is configured to thwart these attacks.

Applications[edit]

The primary purpose of an expansion card is to provide or expand on features not offered by the motherboard. For example, the original IBM PC did not have on-board graphics or hard drive capability. In that case, a graphics card and an ST-506 hard disk controller card provided graphics capability and hard drive interface respectively. Some single-board computers made no provision for expansion cards, and may only have provided IC sockets on the board for limited changes or customization. Since reliable multi-pin connectors are relatively costly, some mass-market systems such as home computers had no expansion slots and instead used a card-edge connector at the edge of the main board, putting the costly matching socket into the cost of the peripheral device.

In the case of expansion of on-board capability, a motherboard may provide a single serial RS232 port or Ethernet port. An expansion card can be installed to offer multiple RS232 ports or multiple and higher bandwidth Ethernet ports. In this case, the motherboard provides basic functionality but the expansion card offers additional or enhanced ports.

Physical construction[edit]

One edge of the expansion card holds the contacts (the edge connector or pin header) that fit into the slot. They establish the electrical contact between the electronics on the card and on the motherboard. Peripheral expansion cards generally have connectors for external cables. In the PC-compatible personal computer, these connectors were located in the support bracket at the back of the cabinet. Industrial backplane systems had connectors mounted on the top edge of the card, opposite to the backplane pins.

Depending on the form factor of the motherboard and case, around one to seven expansion cards can be added to a computer system. 19 or more expansion cards can be installed in backplane systems. When many expansion cards are added to a system, total power consumption and heat dissipation become limiting factors. Some expansion cards take up more than one slot space. For example, many graphics cards on the market as of 2010 are dual slot graphics cards, using the second slot as a place to put an active heat sink with a fan.

Some cards are 'low-profile' cards, meaning that they are shorter than standard cards and will fit in a lower height computer chassis. (There is a 'low profile PCI card' standard^[1] that specifies a much smaller bracket and board area). The group of expansion cards that are used for external connectivity, such as network, SAN or modem cards, are commonly referred to as input/output cards (or I/O cards).

Daughterboard[edit]

A daughterboard, daughtercard, mezzanine board or piggyback board is an expansion card that attaches to a system directly.^[6] Daughterboards often have plugs, sockets, pins or other attachments for other boards. Daughterboards often have only internal connections within a computer or other electronic devices, and usually access the motherboard directly rather than through a computer bus.

Daughterboards are sometimes used in computers in order to allow for expansion cards to fit parallel to the motherboard, usually to maintain a small form factor. This form are also called riser cards, or risers. Daughterboards are also sometimes used to expand the basic functionality of an electronic device, such as when a certain model has features added to it and is released as a new or separate model. Rather than redesigning the first model completely, a daughterboard may be added to a special connector on the main board. These usually fit on top of and parallel to the board, separated by spacers or standoffs, and are sometimes called mezzanine cards due to being stacked like the mezzanine of a theatre. Wavetable cards (sample-based synthesis cards) are often mounted on sound cards in this manner.

Some mezzanine card interface standards includethe 400 pin FPGA Mezzanine Card (FMC);the 172 pin High Speed Mezzanine Card (HSMC);^[7][8]the PCI Mezzanine Card (PMC);XMC mezzanines;the Advanced Mezzanine Card;IndustryPacks (VITA 4), the GreenSpring Computers Mezzanine modules;etc.

Examples of daughterboard-style expansion cards include:

• Enhanced Graphics Adapter piggyback board, adds memory beyond 64 KB, up to 256 KB^[9]
• Expanded memory piggyback board, adds additional memory to some EMS and EEMS boards^[10]
• ADD daughterboard
• RAID daughterboard
• Network interface controller (NIC) daughterboard
• CPU Socket daughterboard
• Bluetooth daughterboard
• Modem daughterboard
• AD/DA/DIO daughter-card
• Communication daughterboard (CDC)
• Server Management daughterboard (SMDC)
• Serial ATA connector daughterboard
• Robotic daughterboard
• Access control List daughterboard
• Arduino 'shield' daughterboards
• Beaglebone 'cape' daughterboard
• Raspberry Pi 'HAT add-on board'^[11]
• Network Daughterboard (NDB). Commonly integrates: bus interfaces logic, LLC, PHY and Magnetics onto a single board.

Standards[edit]

• PCI Extended (PCI-X)
• PCI Express (PCIe)
• Accelerated Graphics Port (AGP)
• Conventional PCI (PCI)
• Industry Standard Architecture (ISA)
• Micro Channel architecture (MCA)
• VESA Local Bus (VLB)
• CardBus/PC card/PCMCIA (for notebook computers)
• ExpressCard (for notebook computers)
• Audio/modem riser (AMR)
• Communications and networking riser (CNR)
• CompactFlash (for handheld computers and high speed cameras and camcorders)
• SBus (1990s SPARC-based Sun computers)
• Zorro (Commodore Amiga)
• NuBus (Apple Macintosh)

See also[edit]

• M-Module, an industrial mezzanine standard for modular I/O

References[edit]

1. ^ ^ab'PCI Mechanical Working Group ECN: Low Profile PCI Card'(PDF). Pcisig.com. Retrieved 2012-11-17.
2. ^'MB-54VP'. ArtOfHacking.com. Retrieved 2012-11-17.
3. ^'NX586'. ArtOfHacking.com. Retrieved 2012-11-17.
4. ^'LEOPARD 486SLC2 REV. B'. ArtOfHacking.com. Retrieved 2012-11-17.
5. ^'Motherboards'. Artofhacking.com. Retrieved 2012-11-17.
6. ^ IEEE Std. 100 Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, IEEE, 2000,ISBN0-7381-2601-2, page 284
7. ^Jens Kröger.'Data Transmission at High Rates via Kapton Flexprints for the Mu3e Experiment'.2014.p. 43 to 44.
8. ^Altera.'High Speed Mezzanine Card (HSMC) Specification'.p. 2-3.
9. ^Market Looks to EGA as De Facto Standard, InfoWorld, Aug 19, 1985
10. ^Product Comparison: 16-Bit EMS Memory, InfoWorld, Sep 7, 1987
11. ^'Add-on boards and HATs'. GitHub. Raspberry Pi Foundation. Retrieved 19 June 2020.

External links[edit]

Summary :

Are you confused about PCI and PCIe? If you don't know how to distinguish them, you can read this post, in which MiniTool explains their differences to you from 4 aspects: function, appearance, speed, and compatibility.

What Are PCI and PCI Express?

In the computer, if different devices want to exchange data, they must do that via a certain channel, that is, bus. Bus is a common communication trunk line for transmitting information between various functional parts of a computer. It is a transmission wiring harness composed of wires. Both PCI and PCIe are buses.

What Does PCI Do in a PC?

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PCI is shorthand for Peripheral Component Interconnect, which is a local bus in PC. Then, how does it work in computers? I will explain that in this part.

Many years ago (around 2000-2010), the computer motherboard is constructed like the following picture:

This structure is a typical North-South Bridge chip structure based on PCI bus. CPU and Northbridge chip are connected via FSB (Front Side Bus). The Northbridge chip is mainly responsible for controlling data exchange between CPU and high-speed devices (AGP graphics card, memory).

Then, Southbridge is connected to Northbridge via an internal bus (like Hub-Link). The Southbridge chip is mainly responsible for data exchange of low-speed devices like floppy drive, hard disk, keyboard, and add-in card.

Where is PCI? It's under Southbridge. Under Southbridge, there are many buses: PCI, LPC (Low Pin Count), SATA, USB, etc. PCI bus is mainly responsible for connecting devices like network card, audio card, and SCSI card. LPC bus is mainly responsible for connecting common low-speed devices like BIOS, keyboard, mouse, floppy disk, etc.

This article explains deeply what SATA SSD and M.2 SSD are. It touches upon SATA Bus standard, PCI-E Bus standard, AHCI protocol, and NVMe protocol.

What Does PCI Express Do in a PC?

What is PCI Express? PCI Express, also called PCIe/PCI-E, is the successor of PCI and AGP. In addition, it is gradually taking place of SATA and USB buses. A typical motherboard structure based on PCIe is shown like the following picture:

The above picture shows the structure of Intel Z390 motherboard that was launched at October 8, 2018. In this motherboard, Northbridge is totally integrated into CPU, so there are only two main parts: CPU and Southbridge (Intel calls it I/O Control Hub or Platform Controller Hub).

Similarly, the graphics card and memory are directly connected to CPU. But there are two points you should pay attention to: a. the graphics card is connected to CPU via PCIe bus; b. the motherboard supports direct connection between CPU and PCIe SSD.

Then, Intel Z390 chipset (Southbridge) is connected to CPU via DMI (Direct Media Interface) 3.0 bus that is based on PCIe bus. The Southbridge distributes 24 PCIe lanes used for connecting hard drives, USB devices, network card, audio card, etc. It can be said that PCIe is not just a local bus. It is already a system bus.

When you read here, you might be thinking 'where is my M.2 PCIe SSD plugged in?' Actually, there are two situations:

• Your graphics card uses PCIe 3.0 X8 lanes and other two PCIe 3.0 X4 ports are used to insert 2 NVMe SSDs. In this situation, the SSDs are connected to CPU directly, so that each of them can enjoy 4 GB/s throughput exclusively.
• Your graphics card uses PCIe 3.0 X16 lanes and your M.2 PCIe SSD shares 24 ICH/PCH PCIe lanes with other devices. In addition, the speed of SSDs will be limited by DMI 3.0 (the speed of DMI 3.0 X4 equals about that of PCIe 3.0 X4). That' why Thunderbolt 3, M.2, and U.2 interfaces are currently unable to break through the PCIeX4 bandwidth.

In most cases, your computer takes the second layout. Even though PCIe SSDs share throughput with other devices, they are still faster than other SSDs like SATA SSDs. Besides, the additional devices on the Southbridge will not operate all together usually, so the throughput of DMI 3.0 is sufficient.

This post introduces NVMe vs M.2 vs PCIe in detail. After reading this post, you can know the differences between them clearly.

PCI vs PCIe

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In this part, I will explain PCI vs PCI Express from 3 aspects. Read on to learn about differences between PCI and PCIe further.

PCI vs PCIe Slot

In this part, I will show you what PCI and PCIe slots look like. The first one I will introduce is PCI slot. This slot has two types: 32-bit slot with 124 pins and 64-bit slot with 188 pins. The former is usually used in general desktop computers and the latter is generally used on servers. The PCI slot looks like the following picture:

Then, it's the turn to introduce PCIe slot. This slot has 7 versions: x1, x2, x4, x8, x12, x16, and x32, corresponding to 1/2/4/8/12/16/32 lanes, respectively. Among them, PCI-E x32 is only used in some special occasions due to its large size and there is almost no corresponding mass-production product.

PCI-E x12 is mainly used in servers and will not appear on consumer platforms. PCI-E x2 is mainly used for internal interfaces rather than expansion slots. Even if some motherboards provide this interface, PCI-E x2 basically appears in the form of M.2 interface instead of PCI-E slot.

Therefore, the mainstream PCI-E slots on the motherboard are basically concentrated on the four types: PCI-E x1 / x4 / x8 / x16. Let's introduce them in more detail:

• PCI-E x16 slot: It is 89mm long and has 164 pins. It is often used for graphics cards and backward compatible with x1 / x4 / x8 devices.
• PCI-E x8 slot: It is 56mm long and has 98 pins. It usually appears in the form of a PCI-E x16 slot, but only half of the data pins are valid, which means that the actual bandwidth is only half of the true PCI-E x16 slot. The purpose is to allow the graphics card with PCI-E x16 interface to be smoothly installed on the PCI-E x8 interface.
• PCI-E x4 slot: It is 39mm long and has 64 pins. It is mainly used for installing PCI-E SSDs or M.2 SSDs (through PCI-E adapters). But in most cases, the PCI-E x4 slot comes in the form of an M.2 interface when it leaves the factory.
• PCI-E x1 slot: It is only 25mm long and has 36 pins. The products targeted are relatively extensive, including independent network cards, independent sound cards, USB 3.0 / 3.1 expansion cards, etc.

Then, the PCI-E x1 / x4 / x8 / x16 slot looks like the following picture:

PCI vs PCIe Speed

In this part, I will explain PCI vs PCI-E speed. After learning about their speed differences, you will know why PCI interface is replaced by PCIe interface.

The 32-bit PCI speed is 133 MB/s, while the 64-bit PCI speed is 266 MB/s. As for PCIe speed, it varies depending on lanes and versions. Let's look at the PCIe performance diagram offered by Wikipedia:

At present, most computers use PCIe 3.0 version. With this version, even PCIe x1 can be much faster than 64-bit PCI. In terms of PCI vs PCI-E speed, PCI-E is winner and it totally takes the place of PCI.

Do you know what SSD drive is? This article will explain some SSD Terminologies and help you to fully understand SSD disk.

PCI vs PCIe Compatibility

In terms of compatibility, there are several points you should remember:

1. PCI: The 32-bit PCI interface is not compatible with 64-bit PCI products, while the 64-bit PCI interface is compatible with 32-bit PCI products.
2. PCIe: PCI-E interfaces have different lengths. The more lanes it has, the longer the interface. Generally, long slots are compatible with short interface products. For example, PCIe X16 slot can be compatible with X4 or X8 products. But short slots cannot be compatible with long interface products because they cannot be inserted.
3. PCIe: PCIe has different versions. Different versions are compatible with each other. For example, PCIe 3.0 is compatible with PCIe 2.0. But the performance is determined by the low version.
4. PCI vs PCIe: The PCI-E interface and the PCI interface are not compatible with each other.

Migrate Computer to PCIe SSD

After learning about PCIe vs PCI, you may want to use PCIe produces. If your computer has PCI-E interface, you can certainly enjoy the high speed of PCIe. In this part, I will show you how to migrate OS to a PCIe SSD with MiniTool Partition Wizard. In this way, you can use your PC on new hard drive without reinstalling OS.

This post provides a step-by-step guide on how to install a second hard drive in the laptop and desktop PC.

Here is the tutorial:

Step 1: Click the above button to buy MiniTool Partition Wizard. Install it and then open it to get its main interface. Click on Migrate OS to SSD/HDD in the toolbar.

Step 2: Choose the right method to migrate the system disk and click Next.

Option A: to replace the system disk with another hard disk: The entire system disk will be copied to the new SSD. The data includes system files and your personal files on other partitions.

Option B: to move operating system to another hard disk: Only the system and boot partitions required for OS are copied to the new SSD. Your personal files are still on the original disk.

Step 3: Choose the new SSD to migrate Windows to and click Next. A warning window will pop up. Read it and click Yes.

Step 4: Choose right copy options and adjust the target disk layout, and then click Next.

(1). Fit partitions to entire disk: All the partitions on the original disk are shrunk or extended by an equal proportion to fill the entire target disk.

(2). Copy partitions with resizing: All the partitions on the original disk are copied into the target disk without changes in size or location.

(3). Align partitions to 1 MB: It is recommended for improving computer performance.

(4). Use GUID partition table for the target disk: MBR can only recognize and use 2TB disk space at most. This option can convert MBR to GPT, thus users can use the disk space beyond 2 TB.

Step 5: Read the note and click Finish, then click Apply on the toolbar to execute the pending operations.

Step 6: MiniTool Partition Wizard will ask for a reboot. Click Restart Now.

Bottom Line

Has this post helped you learn about PCI vs PCIe? Do you have any opinions about PCI and PCIe? Please give us feedback in the following comment zone. Besides, if you have difficulty in migrating OS to PCIe SSDs, you can contact us via [email protected]. We will reply to you as soon as possible.

PCI vs PCIe FAQ

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