Examining ATX

The ATX form factor was designed by Intel back in 1995 to improve on the AT form factor. It brought about changes that would help standardize placements with various types of hardware, one being full length expansion cards; in original AT layouts the processor sockets were positioned at the front of the motherboard which kept full length expansion cards from being used. Now that the ATX form moved the CPU sockets to the back right corner of the motherboard full length PCI/ISA cards had plenty of room.

AT also had the problem with drive bay interference since the AT motherboards were longer from front to back. With ATX the motherboard is cut wider, instead, to provide some clearance between drive bays and the board itself. Moving the CPU socket also aided in this change since there was a need for board space at the back right instead of the front left corner of the motherboard.

Some of the other changes from AT to ATX:
  • Power supply connection
  • AT motherboards used dual 6-pin connectors to power the system which was confusing and also potentially dangerous if we did not know what went where. The ATX specification implements a single 20-pin connection from the power supply to motherboard to eliminate confusion and damage to hardware.

  • Power management
  • The older AT specification also had the power button of the case hard wired directly to the power supply. The ATX specification implements the "Soft Power" feature which allows the motherboard to turn the power supply on and off by software. For example, when shutting down the Windows OS in an AT set up the system needed to be manually shut down by pressing the power button. The ATX form factor allowed the system to be automatically powered down after the OS logged off.

  • Integrated I/O, peripheral connections
  • On older AT boards, instead of having the parallel and COM ports we see at the back of the motherboards, extra cables were required to extend those features to the case. We needed to run cables from pin headers on the motherboards and mount them to the cases to be able to connect printers or other devices that used these ports. When the ATX form factor was introduced, these connectors were soldered directly on to the motherboard to both reduce the time to install components and the overall cost of a system, as well as to increase the reliability of the ports.

  • Cooling and air flow
  • Moving the CPU to the back right of the case closer to the power supply and the backside fans had a positive effect on cooling. Warm air created by the CPU would be pulled out through the back of the case as well as up through the power supply if it had a fan facing the CPU.
With the AT form factor, the CPU was at the center of the case and required more fans to cool the entire system. Moving the hottest component off to a side of the case meant more stable temperatures for other components like HDDs and memory.

The ATX had a clear goal in mind; a new design that would reduce clutter, standardize component design and bring more control to the motherboard.  The BTX mandate is a little less clear; reduce the PC footprint while more efficiently cooling the components.  Keep this mandate in mind as it plays heavily on our conclusion.

Index Examining BTX
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  • L3p3rM355i4h - Thursday, February 10, 2005 - link

    Seems to be good for the OEM market, but what about us people who *actually* care about computers? Front exhuaust has to be the stupidest thing ever. Why was it so hard just to reverse the layout, so it would be atleast somewhat compatable with the current ATX standard.

    And the guy/gal who made up the "ATX II" standard, maybe you should contact AMD or someone. They might be interested.
  • EthernaL - Friday, May 19, 2006 - link

    What if I really LIKE my BIG ATX tower?
    Maybe I have temperature problems in summer... maybe is not all the efficient that could be but I really love this design and I don't want to move to a small design and I don't want to buy the whole thing again.

    Another nice thing with the computers we currently have is the possibility to give our friends/relatives old pieces once we upgrade our computer (my sister's computer is build that way :P )

    So, again, another decission based ONLY on money without thinking in what we (the users) want or need. Thanks Intel, I hate you more than ever, and if you 'force us' to move to that technology I hope your business will go bankrupt.
  • IntelUser2000 - Sunday, November 21, 2004 - link

    "From the picture we see the flow of air pushed back through the CPU thermal module towards the Northbridge, Southbridge, and VGA card. As this air flows around the CPU, it warms up, as we can see from the red areas to the left and right of the CPU. This warm air then flows over the Northbridge and seems to cool as it travels further back in the chassis. At the left we see the channel of air flowing to the left over the memory and out through the PSU. The channel on the right flows straight back to the VGA card and out through groups of holes in the back of the case."

    Well doesn't look like to me that hot air comes out front.
  • MadAd - Friday, November 19, 2004 - link

    One question im having in my mind is how big of a paintbrush will i need to get inbetween those fins - talk about a dust trap.

    At least a majority of atx heatsink designs have easy to clean fins, and boy do they need cleaning sometimes, this is going to be worse.

    Cue the repair calls in years to come, $50 an hour for removing wads of the customers cat/dog/children from around the cooler after the safety backoff system renders the machine temporatily gonadless.
  • epiv - Thursday, November 18, 2004 - link

    Intel can and should make BTX backward and forward compeitable with ATX so we can decide if a new BTX case and PSU is worth the money.
    I am a poor student and I already spend money on a good case and PSU. My case should be able to handle more heat than a regular BTX case. I really hope I will not have to get a new case and PSU when I upgrade my computer.
  • trikster2 - Wednesday, November 17, 2004 - link

    facts? I actually own the silverstone version of the oppus case, so I am actually speaking from experience. Vertical vs horizontal lowprofile vs full height has a lot to do with heat disapation
  • Myrandex - Tuesday, November 16, 2004 - link

    I wonder how BTX had a NDA because Gateway has been selling BTX computers at best buy for over a month at least
  • Cygni - Tuesday, November 16, 2004 - link

    Dont you bring facts into this, Kris! Trikster2 doesnt want any of that!
  • KristopherKubicki - Tuesday, November 16, 2004 - link

    trikster2: The Opus case was chosen because it was the same volume as the mBTX case. I don't really see how a mATX tower and an mBTX case are going to differ significantly.

  • ceefka - Tuesday, November 16, 2004 - link

    How can this possibly translate into lower cost for end users? Thank you, Intel.

    I am also disappointed by Intel's approach. Uhm, we have a hot CPU; let's make a cooler case!

    Since they invented this in their own backyard without creating a wide support it looks like an ego-trip.

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