BTX - The Basics

Just in case you were told otherwise, the BTX form factor is largely incompatible with the ATX form factor - the only area where this doesn't fully apply is in power supply support, as you can use ATX power supplies with BTX motherboards (more on this later).

In order to understand BTX you have to understand the motives for change. CPUs are getting hotter, graphics cards are as well, and despite all of these increases in thermal dissipation there is an increase in demand for quieter PCs. Today's ATX cases and motherboards were not designed for the incredible levels of heat that they have to deal with, and it is with this that we begin our understanding of BTX.

Pictured below you will see a BTX motherboard reference design:

The first thing that you'll notice about the BTX form factor is that the expansion slots have switched sides. In the picture above you'll see a total of 7 slots, from left to right we have a PCI Express x16 slot, two PCI Express x1 slots and four 32-bit PCI slots. Note that the slot closest to the CPU is the PCI Express x16 slot, which will be used for graphics, allowing it to share some of the CPU's cooling.

The redesign of the board layout was done in order to improve airflow through the system; moving the CPU to the "front" of the case allows it to be right next to the intake fan, giving it the coolest air out of any component in the system. You will then notice that the chipset is directly in line with the CPU, allowing airflow over the CPU's heatsink to be channeled over those heatsinks as well before exiting the case. This direct line of airflow allows for very efficient cooling of not only the CPU, but the voltage regulators, chipset and graphics card.

The memory slots have been moved to the left edge of the motherboard, but are also able to receive cooling courtesy of the thermal module, as it is known, that is mounted over the CPU. You can see a good example of what the thermal module will look like below:

The white plastic duct encloses what is known as the "thermal module," which at this point is basically a heatsink and a fan. In the future, the thermal module could encapsulate some more exotic cooling forms such as heatpipes or potentially even water cooling. In this particular design, the fan seen above is a 90mm unit.

In order to understand the cooling flow within a BTX system, take a look at the picture below:

In the depiction above the graphics card is mounted on a riser card, although it can also be mounted vertically.

Index Three Different BTX Sizes
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  • small - Monday, January 19, 2004 - link

    According your post, I have some following question,
    "The BTX standard covers two case heights as well. Type I for cases of 3.98 inches high and Type II for small design case at only 3 inches high. Type I use normal expansion cards while Type II will either use risers or be low profile design cards."

    Is that mean type I 3.98 inches high is for microBTX case?
    And type II 3 inches is for picroBTX case? Is that right?
    But the case size shoudn't design by manufacturers themsleve?

    2.You said ATX power supply can be use in BTX motherboard?
    But according to the design guide of CFX12V power supply which issued by intel,
    (CFX12V power supply is designed to support BTX systems).
    The most different between CFX12V and ATX12V power supply ,
    I think it should the physical dimension & main power connector to motherboard.
    Due to the shape of CFX12V is different than ATX12V, so how can standard ATX12V power supply can be sued for BTX??
    And also the power connector (motherboard) for CFX12V is 24PIN,and ATX12V is 20P.

    why ATX12V power supply can be used in BTX motherboard and computer case?

  • MasterOfPuppets - Thursday, January 15, 2004 - link

    I would like to say to #85 that this new form fator was designed for less heat. I would not say that computer companies are losing money no their computers. they screwed themselves and are looking for a way out. they offered too much porcessing power to the market, and now the AJ(average joe) has more processing power than he knows what do do with it. HE can do everything he can imagine on it(lets just say hes kinda dumb to average with computers).the AJ doesnt need to buy another computer, b/c he has excess power to check his email and surf the web. it supply and demand, the demand plateaued but the supply of great new better technology took off.the computer companies have an excess of computer parts sitting around and the only way to get rid of them in a sensable way is to change formats and declare the old ATX obsolete. the AJ doesnt need a 3Ghz comp, but he has one and for him hes set for a couple of years. the computer companies want his money and if he doesnt buy a comp for 3+ years then the computer companies arent making too much. this is exactly why the format is changing, and if u dont believe me you can float around in your dream word where the computer companies are your friends. Back to the heat part of the case. as stated before in this forum there are cheaper meathods to get more cooling(rather than buy a new computer), and the AJ doesnt give a crap about his computers heat, it is a way to cover up the computer companies true motives(like all other companies in a captialist society, to get your money.)the only people that truely care about their computer's heat are tweaker's and it is true that they are not in the business equation, but the AJ isnt going to care about the new format if his computer works fine and does what it needs to do,surf the internet, which i should add is a very demanding this new foramt is a business decision and they had to make this decision to get themselves out of a deep hole they dug. I would like to add that i will be the very last if ever person to switch to BTX(Broken Technology eXtended, i liked that quote) and i hope that their business decision leads them to a very dark and nasty place.
  • MasterOfPuppets - Thursday, January 15, 2004 - link

    This so called new technology just another way to get your money. Why cant ATX components be compatable, because that would decrease the amout of money that computer companies get. I currently have a lot of money invested in my computer and have little intention to buy a bunch of new parts because my current ones arent compatable with this crappy re-arranged motherboard. If people really want some heavy duty, silent cooling make water cooling more common, dont make peol buy a whole new computer just so that it will be cooler. i dont know how many of u got that out of that article, but if ur current computer is too hot do u want to go and buy a new one that only slightly colder? HELL NO! i refuse, and the computer companies can kiss my a$@!!
  • zookus - Wednesday, October 29, 2003 - link

    For those of you who haven't yet had a chance to see it, here are the specifications for just about everything relating to the BTX standard:

    What concerns me is that according to this, even the largest cases will only have room for ONE hidden 3.5" device. Sort of screws my RAID array. Has anyone heard word otherwise?
  • Anonymous User - Sunday, October 19, 2003 - link

    o pa isto pra min é cona...cona e cu...por min tas bem agora atx e abx ou o caralhu
    venha a cona
  • Anonymous User - Saturday, October 4, 2003 - link

    #91 again this would only work well on tower cases
  • Anonymous User - Saturday, October 4, 2003 - link

    why can't they use isoecletric cooling modules like they have in coolatron camp coolers? are they too big or do they draw too much power? Put two on the bottom and the hot air rising would pull coolair up from the bottom .You have intake vents on the bottom below the cooling modulesand exhaust vents on the top of the case.Normal convection might not need fans. As the air gets hotter up top the more air it would pull up from the bottom.Just a matter of sizing the ventsand adding a thermostat.I might try it on my ATX I' building. Let ya know if it works.
  • Anonymous User - Saturday, September 27, 2003 - link

    Moving the chairs on the Titanic. Intel needs to go back to the drawing board and start putting Pentium M's on the Desktop instead of Pentium 4's. That would instantly eliminate the need for form factor changes, thermal modules, etc...Besides saving an incredible amount of energy (not that this is important).
  • Anonymous User - Friday, September 26, 2003 - link

    Will the Hollings chip be on the BTX mobos?
  • Anonymous User - Thursday, September 25, 2003 - link

    A lot of you are assuming that the things that you want is what everyone else wants as well. I've had a big 3d cool case for quite some time with plenty of active cooling, and honestly, i'm getting really really sick of it. I want something small, sleak, and quiet. So what if you have to buy a new case, deal with it, things like this happen now and then, you can't expect to use the same case for the next 50 years.

    You can't judge how this will all work from one preview, wait for some decent boards and cases to hit and then look over the reviews, and then you can decide. Everyone just calm down and accept that change isn't a bad thing.

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