ATX (from the English. Advanced Technology Extended ) is a form factor of personal desktop computers . Is the dominant standard for mass-produced, since 2001 , computer systems.
The ATX standard defines the following characteristics:
- geometrical dimensions of motherboards ;
- general requirements for the position of connectors and openings on the case;
- the shape and position of a series of connectors (mainly power);
- geometrical dimensions of the power supply ;
- the position of the power supply mountings in the case;
- electrical characteristics of the power supply;
Content
History
Developed and offered to computer system manufacturers in 1995 by Intel to replace the AT used for a long time. In addition to Intel itself, the replacement began to be made by OEM suppliers ( HP , etc.), then it was picked up by the suppliers of components - motherboards and power supplies for them . The mass ousting of the former standard occurred at the end of 1999 and the beginning of 2001 . Other modern standards ( microATX , flexATX , mini-ITX ) usually retain the main features of ATX, changing only the size of the board and the number of expansion slots.
During its existence, the ATX specification has undergone a number of changes expressed in the standards:
- ATX 1.0 Standard;
- ATX 1.1 Standard;
- ATX 1.2 Standard;
- ATX 1.3 Standard;
- ATX 2.0 Standard;
- ATX 2.01 Standard;
- ATX 2.1 Standard;
- ATX 2.2 Standard;
- ATX 2.3 Standard;
- ATX 2.31 Standard;
- ATX 2.32 Standard;
- ATX 2.4 Standard;
In 2003, Intel announced a new standard - BTX , in particular, aimed at improving the cooling efficiency of the computer system unit . The main calculation of the company for the replacement of ATX was associated with the ever increasing dissipated thermal power of computer components, primarily processors. The beginning of the format change soon ceased - the majority of the computer industry has abandoned the mass distribution of the new format due to the steady downward trend in the power dissipated by computer components.
As of 2017, the ATX form factor and its derivatives remain the most widespread and are not planned to be replaced in the near future.
The main differences between ATX and AT
- CPU power is controlled by the motherboard. To ensure the operation of the control unit and some peripheral devices, even when it is turned off, a duty voltage of 5 and 3.3 volts is applied to the board. Although many instructions for safely replacing components strongly suggest disconnecting the power cord from an outlet, many ATX power supplies have a break switch on the case.
- The fan on the rear wall of the power supply unit can be supplemented (or replaced) with a fan of 12-14 cm in size mounted on the bottom of the power supply unit, which allows you to create a larger air flow at lower speeds and, consequently, less noise. The arrangement of elements on the motherboard is oriented so that the processor heatsink is in the path of the air flow from the power supply fan. At present, there is a tendency to separate the air flow: the power supply unit is placed down the body, the air flow to it comes either from under the body or (less often) from the inside, from the video card. In the original ATC specification, the power supply fan located at its bottom was supplied with respect to the case and was intended to blow the CPU radiator.
- The power connector has changed: in order to avoid erroneous connections of two similar power connectors in the previous standard, in the ATX standard, the key connector has an unambiguous connection. Due to the increase in computer power consumption, the number of contacts in the ATX power connector first increased to 20, then to 24; at the same time additional connectors appeared: first 4- and then 8-pin, connecting 12 V via a separate power line.
- The rear panel has changed: in the AT standard, there was only a hole for the keyboard connector on the rear panel, boards installed in expansion slots and “braces” with connectors connected to the motherboard by means of flexible loops were installed in slot slots; in the ATX standard, the keyboard (and mouse) connectors are traditionally located on the top, the rest of the space on the rear panel is occupied by a rectangular hole of a fixed size, which the motherboard manufacturer can fill with connectors in any order. Included with the motherboard is a “plug” ( English IO plate ) with slots for the connectors of a specific motherboard (this allows you to use the same case for motherboards with completely different sets of connectors). Additional functions of the "plug" - reducing the radiated EMI and the formation of a single chassis ground loop.
Board sizes
Size name | Size in mm | Size in inches |
---|---|---|
WTX (Workstation Technology Extended) | 356 × 425 | 14 × 16.75 |
EE-ATX | 347 × 330 | 13.7 × 13 |
E-atx | 305 × 330 | 12 × 13 |
XL-ATX | 345 × 262 | 13.5 × 10.3 |
ATX | 305 × 244 | 12 × 9.6 |
Mini-ATX | 284 × 208 | 11.2 × 8.2 |
Micro-atx | 244 × 244 | 9.6 × 9.6 |
Flex-ATX | 229 × 191 | 9 × 7.5 |
Mini-ITX | 170 × 170 | 6.7 × 6.7 |
Nano-itx | 120 × 120 | 4.7 × 4.7 |
Pico-itx | 100 × 72 | 4 × 2.8 |
Mobile-ITX | 75 × 45 | 2.9 × 1.8 |
Power Supply
During the development of the standard (from 1995 to 2004 ), the standard for the power supply connector has changed, while ensuring compatibility with previous standards.
20-pin ATX connector (view of the motherboard)
24-pin ATX connector (view of the motherboard)
20-pin connector
Used before the emergence of motherboards with bus PCI-Express
- 5V VSB (standby) - “stand-by” power supply 5 V, which is supplied before switching on the main power supply of the board
- PW OK - power supply (5 V and 3.3 V) in order
- PS ON # - 14th contact - when closed to ground or to contact PW OK (Gnd), 15th contact - the power supply turns on, turns off when switched off (it is undesirable to switch on without load).
- Gnd (ground) - " land "
24 pin connector
Used on PCI Express bus cards , for which additional power has been added 4 more contacts.
For compatibility with old boards that have a 20-pin connector, most of the power supply units have an additional 4 contacts detached from the main block. If PCI-Express is not used, most motherboards designed for a 24-pin connector can work with a 20-pin one.
Additional 4-pin plug
With the advent of Pentium 4 and Athlon 64 processors , the new ATX12V 2.0 standard boards appeared, using 12 V bus for the main power supply (instead of 3.3 / 5 V as before). Subsequently, with an increase in the load on this bus and an increase in the power consumption of the processors, the need arose for an additional 12-volt connector (ATX12V v2.2) for the processor. This connector is usually located on the board somewhere near the processor.
24 + 4 + 6 pin connector
In addition to the 24-pin connector on the motherboard and 4-pin connector, there may be another 6-pin connector, the same as for the video card power. It is usually installed if the motherboard has a second or more PCI-E 16x port, previously for these purposes a 4-pin Molex connector (PATA) could be used.
24 + 4 + 4-pin connector
In addition to the 24-pin connector on the motherboard and the 4-pin connector, there may be another 4-pin connector (P8), which is combined with the previous one and is a single 8-pin connector (standard EPS12V), usually with a motherboard support more demanding on the CPU power supply, constructively maintains compatibility with the 4-pin power connector. On some high-level motherboards, there may be several such connectors, configurations of 8-pin and 4-pin connectors are possible, or two 8-pin connectors are possible.
See also
- IBM PC-compatible computer
- Motherboard
- The computer case
- Hardware
Literature
- Scott Muller. Upgrade and Repair PC = Upgrading and Repairing PCs. - 17th ed. - M .: "Williams" , 2007. - p. 252-258. - ISBN 0-7897-3404-4 .