What are the X-shaped pieces over the new Mac Pro GPUs?

Discussion in 'Mac Pro' started by nagromme, Jun 16, 2013.

  1. nagromme macrumors G5


    May 2, 2002
    I'm trying to figure out what I'm looking at. What are those X-shaped things with the circle in the middle?

    At first I thought they were just bumpers to make sure the SSD (or SSDs) never hit the GPUs, but the SSD is shown mounted at all 4 corners and will never budge. And they don't look anything like a heatsink. They seem non-functional, yet are bolted in with 4 screws as if they were some major part...

    Some kind of radio shielding maybe?


    Just wondering!
  2. iCheddar macrumors 6502a


    Apr 30, 2007
    South Dakota
    The X shape is the rear of the heat sink mount. Remember, the heat sink is on the inside of the cylinder, not the outside.
  3. derbothaus macrumors 601


    Jul 17, 2010
    Graphics card heat sink brackets. They anchor the mounted cooling system on other side (whatever it is now or just to the thermal core itself) The circle in the center has an offset under view of the chip.
  4. Exponent macrumors regular

    Jul 17, 2002
    Silicon Valley
    I think it's just structural support for the heat sinks. You don't want a lot of mechanical stress going through a high-speed über-dense circuit board.

    Also, the two "X"s give you something to ponder when this shows up at the foot of your bed to guide your transition to the next phase of existence:
  5. nagromme thread starter macrumors G5


    May 2, 2002
    I see. I'm not sure how it's different being braced on both sides instead of only one (the heat sink side being completely rigid already, I'd think), so it seems like the 4 screw-mounts and no brace would be enough--but clearly this has been done before, so I'm sure you guys are right! Thanks.
  6. ValSalva macrumors 68040


    Jun 26, 2009
    Burpelson AFB
    It is the back of the GPU heat sink bracket. I do wonder what the heat sink on the other side looks like, how it connects to the thermal core. This reminds me of the bottom of motherboard CPU heat sink brackets.

    I wonder if there is no GPU heat sink per se, but rather if this bracket connects the GPU directly to the thermal core.
  7. rGiskard macrumors 68000


    Aug 9, 2012
    The bracket works to evenly spread the force holding the GPU against the heatsink for optimal heat transfer. The circle in the center is where the force is directed. It allows the screws to be placed far away from the GPU IO traces and still keep force directly on the back of the GPU. Without the bracket, the circuit board would flex down towards the tightened screws. Some video card designs skip the bracket and cannot acheive the same heatsink to GPU interface pressure.

    It's the number one piece of evidence that the GPUs will NOT be user upgradable, and probably not even upgradable by Apple Stores. You're locked in to whatever GPUs came with the thing. Innovative? Yes, from an accounting perspective, if they can get people to buy the things anyways.
  8. Cubemmal macrumors 6502a

    Jun 13, 2013
    No it's not. How do you replace GPU's now? By installing a new GPU card. How do you install a new mPro GPU? By installing a new card. Which consists of pulling the bottom cover which has a socket to the connector on the GPU board, unscrewing four screws and pulling off.

    Apple, like every single other manufacturer, builds for serviceability, and these are VERY serviceable. How much choice and flexibility they offer us is purely a marketing decision.

    Fascinating, I just noticed, I had assumed that the PC board was the mount point to the chassis. Looking at it, it appears that the X headsink bracket is the attach point. Which makes great mechanical sense. I bet the central heat sink has screw holes which that back bracket is attached too, and that then beautifully lines up the rest of the board. Nice, so the central heatsink truly is the backbone of the unit.
  9. rGiskard macrumors 68000


    Aug 9, 2012

    Umm, no. Thermal interface material is involved, which is generally not considered possible for the average user to properly apply.

    Accessing the card is probably going to be more difficult that you make it sound, but we'll have to wait for more info.

    All this aside, the cards are proprietary, so after removing it there will be nothing to put in its place. Who's going to sell these cards? Apple? That would defeat the primary purpose of this cylinder design, which is to force users to throw out the old and buy new instead of upgrading the old. If Apple do sell card upgrades, it will have to be upgraded by Apple, and the cost will be prohibitive.
  10. rGiskard macrumors 68000


    Aug 9, 2012
    That's the whole idea of the unified thermal core, for the GPUs and CPU to use it directly.

    The photos make it look as if only the GPU interfaces with the core, but I wonder if the vRAM and VRMs will also use the core for heat dispersion.
  11. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Those X shaped things are on the back of almost every AMD GPU I can think of.

    Even lowly 2600XT from 2008 pro has the.

    Image is from 7970s.

    Historically, it has been rare for AMD/Nvidia to get one of their board partners to bother with Mac cards. In the past only mild changes had to be made to existing PC designs, but even these mild changes required retooling and reconfiguring PCB lines, so was rarely done.

    The Quadro 4800 Mac version lost 2 DisplayPort connections and just shipped with Dual DVI.

    The Quadro 4000 Mac they just loped off one DP connection.

    The EVGA GTX285 Mac had a different EEPROM and no S-Video port.

    The AMD 3870 was originally going to be a completely different card but somehow that got cancelled and we ended up with the CHEAPEST version made, identical to PC version but with different EEPROM, no S-Video, and 1 little resistor moved to stop flashing.

    With 4870/5770, and 5870 AMD cards they added MDP ports and lost a DVI or two.

    With these new cards, they appear to be a completely different design than anything shipping anywhere on the planet. Instead of changing a port or 2, the card is a completely custom PCB.

    If Apple doesn't hand out the plans for free, someone else would have to completely re-engineer them. And if Apple hands out the plans, you would still need a special PCB from ground up. ie, you won't just shut down your FirePro line, teach the robots to switch a few pieces out and fire the line back up. All to bring you the wonder and delight of Thunderbolt.

    I don't see a 3rd party even considering this process until they see if these new Mac Pros are selling. This will keep the prices of these cards right up in the stratosphere, where Apple likes them. (Their 5870 is still $450 while a PC one is worth about $150 now)

    There is no way in high holy heck that Apple will let you switch a component that requires re applying thermal compound, so easy to do wrong and fry stuff. So, what GPU you buy your Mac Pro with is likely what will be in it when it heads to the landfill years down the road.

    Attached Files:

  12. Cubemmal macrumors 6502a

    Jun 13, 2013
    I wasn't talking about the user, I'm saying replacing in general. For this that will surely mean by Apple only.

    Doubt it. I work in a similar company to Apple. They design this for serviceability - their serviceability to drive their costs down. The only addition I could see here is another connector we can't see on the backside, but with the heatsink there it seems doubtful.
  13. rGiskard macrumors 68000


    Aug 9, 2012
    Oh, I see where you're going with this. You mean Apple can replace the cards. Well sure, I would hope so. It would be a pretty stupid design if even Apple couldn't service it.

    The problem most of us have with the design is that USERS cannot easily upgrade the video cards. They are locked into the system as it was purchased, with the only upgrade path being a whole new iTube.

    I'm just not seeing what the advantage to this iTube is over buying the same thing from Dell, aside from it running OS X. For me it represents quite a sacrifice in hardware flexibility to run OS X. I despise using Windows so I'll probably have an iTube on my desk at some point, but only because I have no other choice. I don't appreciate Apple bullying me like this. I'm used to it a bit but this is a whole new level of Apple trying to goose-step users into doing it all Apple's way.

    Maybe I'll have another go at Windows. It would be great to build my own tower customized to my needs. I can't believe I'm thinking of going that route...I've used Apple computers since my Apple ][ and have prosyletized for the brand all those years. I do Mac tech support for about a dozen friends and neighbors who were turned onto Macs at my prodding. Now Apple have me thinking about Windows. I guess the iTube really is revolutionizing things...
  14. mrhick01 macrumors 6502

    Sep 22, 2008
    If it really bothers some of you THAT much, maybe getting certified to be an Apple Service Tech would be down your line...then you could upgrade the GPGPUs yourselves when you would want.

    Having enough horsepower to power three 4K displays at once is enough heft to last for at least the next three years...I am bemused by the concern trolling over the Mac Pro video specs.
  15. ScottishCaptain macrumors 6502a

    Oct 4, 2008
    The cards are replaceable by an Apple tech. They are not "user" replaceable (Apple does not document the process in the machine manual), but this isn't going to stop anyone from attempting it if they want to.

    The process is fairly simple. A spudger ("black stick" in Apple terms) is used to pry off the connectors on the bottom of each card. These are aligned by the two pins you can see in the photo, on the connector side there is a field of spring loaded contact points (similar to an LGA socket) that mate with pads on the GPU card. This connector is attached to a flexible ribbon cable that snakes underneath and attaches to the machine backplane.

    The card itself is attached to the thermal core via 6 screws- two in the top left/right corner (there is, unfortunately, an "A" and "B" card- both cards are basically mirror images of each other), and four around the GPU. That's it. The GPU has a proprietary Apple heat spreader on it that extends to the GPU VRAM chips located around the GPU die itself. This mates with a raw copper pad/portion of the thermal core. They use the same thermal paste here as the stuff you get when replacing a processor on a Mac Pro.

    Fun fact about the thermal core: it's not just a solid block of aluminum. Each side is basically a giant vapour chamber (basically a big, flat heat pipe). This is how they are able to distribute the heat across the entire thermal core surface and keep the machine cool- a solid block of copper or aluminum wouldn't do it (you'd get all the heat focused in the centre, and the machine would overheat).

  16. Cubemmal macrumors 6502a

    Jun 13, 2013
    How do you know all this?
  17. ScottishCaptain macrumors 6502a

    Oct 4, 2008
    Early drafts of the service source pages that will be posted to GSX.

  18. nagromme thread starter macrumors G5


    May 2, 2002
    Upgradability is now primarily external, like it or not. You can do most of the same old things... but now in different ways. That's going to sting at first!

    But I like what it means for the future: sharing your pro desktop's "cards" with your laptop at will!

    It will be interesting to see what GPUs can go in a TB2 chassis down the road. (But don't expect to sell the internal GPU!)

    I hope the CPU is socketed, since I don't see that being possible as an external TB2 part. And the RAM and SSD definitely are socketed. Everything else can be done by Thunderbolt.

    I also hope you can configure just a single GPU.

    TB stuff has been slow to arrive (to say nothing of TB2 which isn't even out yet). But it should surprise nobody that the first new pro Mac in a decade is designed for future technology, not designed to make the best of the old.

    Remember the outrage when Apple went USB before the rest of the industry did? Chicken and egg--but peripheral makers will step up.
  19. ScottishCaptain macrumors 6502a

    Oct 4, 2008
    The CPU is socketed in a custom LGA carrier, and has a heat spreader on it.

  20. scottrichardson macrumors 6502

    Jul 10, 2007
    Ulladulla, NSW Australia
    Worth noting that AMD was likely chosen to be the GPU of choice for this machine over nVidia due to AMD's recently beefed up custom chip/board design division - the same division that won them the contracts for not one, but ALL THREE next generation consoles. AMD is more readily able to build custom boards than nVidia currently - so this would have appealed to Apple, given they needed to fit custom PCBs into their nMP.
  21. MeFromHere macrumors 6502

    Oct 11, 2012
    Yes, that's what makes this system so unusual. Most computers are pretty much built around the motherboard. The mechanical engineers figure out how to mount it, find places for all the other stuff, and figure out how to wire everything together. Then they add a box.

    A system like an iMac is built around the screen.

    In the new Mac Pro, the HEAT SINK is the main component. Everything else is engineered to optimize heat transfer.
  22. Cubemmal macrumors 6502a

    Jun 13, 2013
    Yeah, pretty smart design really. I was planning on upgrading my graphics with a new Mac Pro but didn't want a loud system. My present Mac Pro while quiet is still audible. With 3rd party cards Apple can't manage or control the heat, it's up the to the 3rd party.

    This thing should be dead silent. And if not entirely quiet you can easily put it farther away with the TB cables.
  23. fluffyroo macrumors newbie

    Jul 8, 2008
    Columbia, MO
    Does anyone else notice how the new PCI-E SSD Blades seem to have their connectors directly soldered to the GPUs? Wouldn't that require that any possible third party GPU add on to also have PCI-E SSD slots for mounting? If you ask me, it looks like the GPU and SSDs will be sharing a lane of PCI-Express 3.0, which may not make a difference now, but could at some point in the future.
  24. nagromme thread starter macrumors G5


    May 2, 2002
    Meanwhile, we've never even seen the actual "motherboard" (to which at least 4 daughter cards seem to attach: CPU, I/O, and 2xGPU... with the power supply sandwiched between the CPU and I/O).

    Some of Apple's top-view renders do show just a bit of circular motherboard, if you peer down through the thermal core.

    This sounds like a computer where the LEAST expensive part might be the motherboard...
  25. Mr. Retrofire macrumors 603

    Mr. Retrofire

    Mar 2, 2010
    Why not? I like the smell of burned circuit boards in the morning! Tasty!

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