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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  • Anonymous User - Thursday, September 25, 2003 - link

    My understand is that ATX and BTX will co-exist for several years, don't worry , I think.. Reply
  • Anonymous User - Monday, September 22, 2003 - link

    All I know is I want one. PCI Express is gonna rule! BTX sucks.. but I can see using it if they keep making large cases to stick these tiny BTX boards into.

  • Anonymous User - Monday, September 22, 2003 - link

    Hey, it's me #2 again. I think some of us have missed the point of the redesign. It will save OEM manufacturers money to build this system. In case you haven't noticed Intel does not give a crap what the tweaker wants. They made a redesign that will sell to the OEM's cuz it's quieter, smaller, and cheaper to build around. Tweakers didn't buy the ~80 billion PC's last year, the AJ (average joe) did, and he doesn't care bout ATX, BTX or Kiss My X, he just want's a computer that will play his kids games, gets porn on the internet, and doesn't break. For less money. It is a business decision, and you aren't part of the equation. Sorry to inform you. Reply
  • Anonymous User - Monday, September 22, 2003 - link

    As it sits, I see little improvement. From memory, ATX cases were at least backward compatible to AT boards (though ATX boards not so well into AT cases) and the power supplies swappable.

    The ATX case that my computer is in does everything that this does, even has a duct for the CPU air, and _all_ the add-in card slots have airflow.

    I still see no point in doing away with any of the old SuperIO yet, although it doesn't appear that they will try too hard to. I like USB but my mice and keyboards aren't broken yet, I still have a couple working parallel printers. I also can and have developed some serial port projects. For the small guys serial is dirt simple, dirt cheap and has no yearly licence cost to legally sell devices, unlike USB.

    For those that want smaller cases, there are a couple sub-formfactors already in ATX that gives people this.

    PCI-Express (apparently not to be confused with PCI-X) isn't needed yet for graphics is it? Even then, there's no need to dump the ATX form to put this in.

    For the top tier computer makers don't really seem to follow ATX for most of their products anyway, and I doubt BTX will change this as they seem to like this lock-in.

    In short, I am not convinced that this was really needed, make an ATX 2.0 or 1.2, make it at least some cross-compatibility, but completely dumping the form factor with no backward compatibility? I don't think so, and I hope the market rejects it.
  • AbRASiON - Sunday, September 21, 2003 - link

    Oh and to add to my post (AbRASiON #82)

    You guys are crazy if you think they won't design a nice bigger one just the same as our current cases.
    You are also crazy if you think they will FORCE the riser card in - it clearly showed a pic of a board without one in the article and the
    "standard" btx board (far right) looked just like an atx - long and wide
    also _MOST USERS_ want a smaller case - personally I don't care - good, space savings is better for them and they will still make larger cases for
    the overclocking / tweaker type.

    I've moved down from a full tower / mid tower to a stock standard mini (sx 635) - it fits up to 4 or more hdd's and 3 5.25"s and it's designed well.
    room to move, without being a big echo-ey POS.

    Just wait until we see non beta cases from Antec, Lian Li and other good manu's, the cases they show in this article look like the cheap cut your finger metal 15$ cases I was silly enough to buy as a kid.
  • AbRASiON - Sunday, September 21, 2003 - link

    I hated this at first but I think it's actually not that bad.

    You guys have to remember a "stock standard" first series ATX case was a piece of crap.
    Wait until a quality case manufacturer and board manufacturer whip up a case and board like Antec and Asus.

    Also there will be no more (or less) smashing into ram / cpu's / video cards by removing the hard disk cage (Antec SX 635 / 660AMG)
    They can put drive connectors all up the top - and no need to dangle anything down the bottom. (shorter SATA cables)

    I really would like to see the leads for power on / led / hdd / reset to be put in to one standard - it should have been done long ago (hell IBM and Dell? have done it a few times with some of their more proprietry systems, it's so much better)

    Also one standard for front USB / front Firewire and hell front Sound / other ports would be nice too

    Imagine an Antec 660 / 860 / 1060 case. now picture it with a big high quality quiet 12cm fan at the front and a smaller 8cm fan at the back, clearly sucking all the heat straight across the bottom of the case and out the back - any excess heat would raise up to the top where the PSU dual fan would get rid of it - and no heat hanging around "up the top" where the cpu is, cause it's down the bottom.

    Here's what I _DO_ wanna see changed.
    Stock standard SATA cables on power supplies (SATA power)
    a better routing system in cases for power cables
    a better looking power cable (mini mesh sheilding?)
    i'd like to see slide out motherboard trays as stock on all cases
    quick release drive bays
    quick release 5.25" bays
    quick release cards (video / sound) (yes thumbscrews rock, but some ibm's have this cool plastic thing you just kind of lift like a lever and bang all 4 pci slots are free)
    quieter cases (fan / vibration / rattles)
    more rails
    thin (1 / 2 mm) cork sound proofing stuck to the walls of the case
    etc etc

    I want a machine which is very very very quiet and still quite cool and nice quality - I will happily pay 100$ US for a mini / midi tower high quality case with these features.

    We will see what antec can do with this standard, it might not be that bad, honest.

    - AbRASiON
  • Anonymous User - Sunday, September 21, 2003 - link

    Lets just accept it, computers are changing every day, this is just the next step in the cycle. Bring it on BTX

  • Anonymous User - Sunday, September 21, 2003 - link

    My problem is not with buying a new case ,and i do like Intel, best processors out there! (Unless Athlon 64 makes a miracle), still im sticking with Intel. regarding the BTX, i simply don't understand the lack of space! Sure, its trendy to make things smaller, like cellphones!, but lets face it a PC isn't a Laptop!, if i am that concerned with space i buy a laptop(with all the limitations it has), But WHAT ABOUT SPACE???
    The biggest advantage of a PC is its versatility, the possiblity to connect BOARDS inside it. not to mention Hard Drives, CD, DVD, etc etc !

    Sure one could say:" But you can have external devices !!" Oh great!!! My desk will have more wires than a Nasa Command Post ! The Great thing about a pc is its expandability, and BTX's expandability is nearly 0 ! If they want to make a PC like a Console, Absolutely NO problem , BUT they better make it SURE they put EVERY single option there.

    P.S.- The Cooling issue is ludicrous, Its extremely easy to cool down an ATX case.
    I happen to own a Thermaltake Xaser III, and one of the reasons i bought was SPACE!!!!!! 6 internal HD drive bays + 4 front panel 5.25 bays + 2 x 3,5" bays
    And im suppose to go back to the 1980's where most PC's only had space for 1 HDD ? NO WAY !
  • Anonymous User - Sunday, September 21, 2003 - link

    No Way im Spending any cash on this pile of crap! Reply
  • Anonymous User - Sunday, September 21, 2003 - link

    The Apple G5 case design is "revolutionary" - BTX is just a minor tweak.

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