My essay on Thunderbolt ports vs PCIe Slots

Discussion in 'Mac Pro' started by VirtualRain, Aug 20, 2013.

  1. VirtualRain, Aug 20, 2013
    Last edited: Aug 20, 2013

    VirtualRain macrumors 603


    Aug 1, 2008
    Vancouver, BC
    Why Thunderbolt

    This essay starts on the premise that mobile computing is the trend, even amongst creative professionals, and that the PC is in decline, and along with it, vendor interest in developing and supporting PCIe expansion cards for PCs. And we all know that the Mac Pro workstation market is a tiny fraction of that. Those of us who have tried to update our Mac Pros also know how small that market is first hand thanks to the limited selection, poor vendor support, spotty drivers, and often silly compromises we've all come to expect as normal... It's ridiculous to me that we get one or two new GPUs every few years. It's insane that I need to run a power cable from my optical bay to power a USB 3 card because the only choice for native driver support is so poorly designed. It's maddening that finally 3 years after SATA3 SSDs became common, we could find a bootable SATA3 card that wouldn't bottleneck our drives. It's unimaginable to me that I might actually wish this state of affairs continue, never mind be passionately fighting (fruitlessly) for its continuation.

    That brings me to Thunderbolt... What is it really? From a Mac Pro or PC perspective, it's just a PCIe x4 slot turned into a port. From a mobile computing perspective, that's huge... A pair of (switched) x4 PCIe slots on every Mac exposed as a small pair of ports. That takes mobile computing to a whole new level of expansion. And that means, there's a massive potential market for peripherals that plug into this port. A way bigger market than ever existed for PCIe cards for the Mac Pro. It's still early days, but this is a better place to be than in a declining market that couldn't garner much vendor interest.

    Even PC motherboards and laptops are getting in on the game, and PC laptops have just as much to gain from TB as MacBooks and iMacs. This expands the market further and will attract even more vendors and create economies of scale to reduce prices. It's going to take some time but this will reach a critical mass soon enough.

    The new Mac Pro

    Now, how does Apple implement TB ports vs PCIe slots on the new Mac Pro?

    There are three ways to implement TB (which carries DisplayPort video and x4 PCIe for data peripherals) and the three implementations are differentiated by how the DisplayPort signal gets to the TB controller...

    1. IGP on a consumer/mobile CPU providing DisplayPort to the TB controller (Asus is going this route)
    2. Cable kludge that routes DisplayPort from a discrete GPU to the TB controller (ASRock chose this)
    3. Custom GPUs providing DisplayPort to the TB controller (Apple chose this)

    Note that none of these precludes PCIe slots. However, in any of these implementations PCIe lanes are either dedicated to TB or switched/shared with other on-board PCIe peripherals/slots.

    Apple chose to dedicate the PCIe lanes to internal peripherals (dual GPUs and at least one, maybe two PCIe SSDs, and integrated USB3 - the items most of us have added to our own Mac Pros) AND, on top of that, there are three TB controllers (6 ports) that have a x4 bus connection each.

    While many don't/won't see this as a net gain, I do.

    My current Mac Pro cannot have dual high-end GPUs, one or two PCIe SSDs, USB3, and three x4 PCIe peripherals all working at the same time. It simply can't do it. The new Mac Pro can. In fact, the new Mac Pro ships with more capability out of the box than you can possibly configure in the current Mac Pro (since a second high-end GPU covers one of the x4 slots) AND it allows you to add at least three x4 PCIe peripherals on top of that all while driving a trio of 4K displays.

    Apple has chosen a direction which removes the Mac Pros expansion capabilities from the hands of the declining PC market (and all but dead Mac Pro PCIe card market) and puts it clearly in the hands of a market with orders of magnitude more promise... Every Mac sold in the last two generations has come equipped with TB ports and that is starting to get attention. For vendors, they can make a TB product and have a potential market of Millions of Mac owners. And now, Mac Pro owners are going to participate, and likely drive this market further (way more than a new Mac Pro with PCIe slots would) with their deep pockets and demanding requirements for performance .

    Now despite the benefits of having more capability out-of-the-box and plenty of TB expansion, there's still the objection that you can't upgrade your GPU. Of course this is true, but here are a couple of considerations:
    1. Upgrading the GPU in the past has not been widely adopted either... Limited choices offering much if any legit support, power supply constraints, expensive (over priced cards), etc... as a result, only a brave few would bother and even then, it only really makes sense to undertake this every two to three years anyway.
    2. Upgrading the GPU in the past has not been warranted in many workflows and many are still productive after a few years with the GPU that shipped with their system.
    3. Computers are systems and rarely does unlocking one bottleneck not reveal another immediately whereby the ultimate solution is an upgrade of several key components to really unlock new computing potential. At this point it's usually warranted to upgrade the whole system anyway (including CPU, I/O, and GPU).
    4. Many purchasers of computers (especially Mac Pros) are companies that never upgrade assets on a capital depreciation schedule. When a solution no longer meets the need it is replaced.

    The sum of all this is that the number of people truly and negatively impacted by non-upgradable GPUs is small enough to be offset by the benefits of bringing TB to a much larger group of workstation users so they can realize the benefits of greater choice, better support, and more affordable and timely peripherals as discussed earlier.

    Now, here on Mac Rumors, the number of people impacted by non-upgradable GPUs appears high, but these forums are the home to enthusiasts who are the most likely to tinker and upgrade systems so that's expected.
  2. slughead macrumors 68040


    Apr 28, 2004
    I had not thought of this. This is a very good point. However, this is more the fault of Apple for neglecting Mac Pro hardware than it is a problem with PCIe itself.

    If the Mac Pro had actually been updated instead of left to rott on the shelves not-updated (read: still doesn't have on-board USB3, PCIe 3.0, OR SATA III for G_d's sake), your comparison wouldn't be as good.

    Quite simply, you're comparing a computer that is 2 years old and was not designed for dual GPUs (only has two 75 watt power cables, in addition to the lack of physical room) to one that isn't even out yet. Apple sabotaged it's current generation of computers and you're comparing its new design to the old one like it's some technological leap. It isn't.
  3. iamgalactic macrumors regular

    Apr 21, 2010
    oh dear...

    how long before OP is accused of working for apple/drinking the kool-aid?
  4. Cubemmal macrumors 6502a

    Jun 13, 2013
    Good post, very well thought out. Before the new Mac Pro announcement I had been puzzling on how they would solve the ThunderBolt problem. For consumer machines TB is easy; just include a GPU. How would you solve that for a machine where graphics comes in on a PCI card?

    When the new Mac Pro came out I was shocked and wrote it off. The announcement was a disappointment as it wasn't clear how much was upgradable, I thought we might have had another soldered RAM machine which would have been insane. Slowly I've come to realize that it's a brilliant design.

    Yes, the Mac PCI card market is basically non existent and never worked that well anyhow. Every card I've put in my computer has caused grief, except the two graphics cards direct from Apple. This includes common cards like a USB3 and a eSATA. I'm a long time computer hacker and you know, anymore, I'd just rather not mess with it. Give me a computer that just works.

    Finally the message here is that it looks like Apple is trying to save the MP by bringing it more mainstream, which the new form factor accomplishes. I think the price will start at $2,500 as a maximum, and there is a good chance it will start at $1,999 which is possible with the BOM of that machine, and would be a brilliant marketing move. Remember when the iPad came out and everybody was convinced that it would have to cost $800-$1,000? Apple impressed everybody with a $500 starting price, and I think there's a good chance we'll see that same thing at work here.
  5. flat five macrumors 603

    flat five

    Feb 6, 2007
    the leap is in the ventilation system (which ultimately led to the new shape/size).

    that's pretty much the only thing apple themselves designed (though they probably had their hand in thunderbolt design as well? and probably play a consult type role with the other components)..

    everything else is more or less speed bump type of stuff coming from outside sources (faster gpu/cpu/ram/ssd/etc).. if they put the latest&greatest xr4Tinvidia in there.. so what.. that's not a technological leap.. 18 months from now, you'll be complaining about how outdated and unusable the X0Y1Z3 is anyway.


    the leader of that pack is in timeout right now #

    but i'd bet that accusation happened before he finished reading the topic's title.#
  6. freejazz-man, Aug 20, 2013
    Last edited: Aug 20, 2013

    freejazz-man macrumors regular

    May 12, 2010
    awesome to see someone make the argument in such a patient and well-reasoned manner. Could not agree more!

    To complain and say the OP isn't making a valid comparison misses the point entirely as his point isn't to compare to demonstrate the vastly superior technology, but to demonstrate the massively different scales of the peripheral market that can be applied to the different machines. It's basically the entire point of his post. PCIe devices are slim pickings for the mac pro, with thunderbolt opening up the expansion market for the mac pro significantly in theory.
  7. prograham macrumors member


    Jun 9, 2006
    New York
    Nice essay, very well stated. My only gripe with new pro's coming out is going to be running fibre to them. From what I've seen the TB-Fibre adapters are huge and ugly and yet another thing that needs to be plugged into the wall. I'm also not crazy about external storage but obviously the internal hdd landscape is already well into changing.
  8. flowrider macrumors 601


    Nov 23, 2012
    I well thought out thesis. While I may not agree with everything you have to say, you have given me some points to think about.


  9. michelg1970 macrumors regular


    Jul 26, 2011
    Gouda - The Netherlands
    I think the OP is working for Apple. (sure wish I did and then including the stock / option clauses in my contract...)

    LOL. :eek:
  10. ABCDEF-Hex macrumors 6502


    Feb 15, 2013
    Brilliant overview:

    It's great to see someone is looking at the "big picture".
  11. goMac macrumors 603

    Apr 15, 2004
    In before accusations of being paid by Apple...
  12. ActionableMango, Aug 20, 2013
    Last edited: Aug 20, 2013

    ActionableMango macrumors G3


    Sep 21, 2010
    I would hope a new computer has more capability than a 4-year old computer. In any case, that's an unfair comparison for obvious reasons. A fair comparison would be the new MP versus an alternative new Mac Pro with all the capability that you describe, but in a larger case with PCIe slots and internal drive bays. That's the computer I am ultimately defending, not a 4-year old design that everyone knows is outdated.

    You've also cherry picked the requirements to suit your point of view. I could cherry pick the requirement of installing 6 SATA drives inside the case and pronounce that the new Mac Pro has less capability than the current one. I could say that when USB 3.1 comes along I'll be able to add a $20 PCIe card with it, but you'll have to wait a year before someone bothers to do it on Thunderbolt, it will cost three digits, add to your clutter, and you'll have to run a separate power cable too. I could say that there are already 802.11ac cards coming out for $25-$60. When the new MP is 4 years old will wireless users be able to change out its card for the next wireless standard? Are they going to have yet another external box with yet another external power supply? Live with an unnecessarily slow connection? Buy a whole new computer?

    And while you poke fun at the current state of PCIe card expansion, you seem to ignore the current state of Thunderbolt expansion, which is equally ridiculous and buggy, with an extra dash of overpriced:

    • GPU over Thunderbolt is a ridiculous, expensive, crippling hack.
    • Thunderbolt PCIe expansion chassis boxes are extremely limited and overly expensive.
    • External drives, drive exclosures, and adapters have a huge price premium.
    • Thunderbolt ACDs have a port that looks like it should plug right into a MDP port, but are incompatible.
    • Thunderbolt port expansion boxes with firewire/usb hubs like those from Matrox are expensive and buggy. All devices disconnect on sleep and don't come back on wake.
    • Thunderbolt cables are $40.

    So when you complain about expensive video cards and buggy implementations, and hacks, I am confused because while you are not wrong, Thunderbolt is experiencing the exact same problems.

    But I'd also argue that if you are careful, PCIe expansion can be quite wonderful. I now have a $20 PCIe USB 3.0 card that uses native drivers and doesn't require a power cable. I have a PC GPU that blows away Apple's offerings, is less expensive, was extremely easy to install, uses native drivers, uses native power, and works absolutely perfectly in every way.

    And how about those dual cards? Despite years to perfect the technology, SLI and Crossfire are buggy as hell and often limited in their application. I have very low opinion of two card setups, and I feel it remains to be seen how well or how poorly Apple's implementation will work and what software it will work with. What I do know is that we don't see any evidence of Crossfire support in Mavericks. Will the second card only be for OpenCL? Who knows. I'd much rather be able to upgrade to a faster single card than rely on a dual card setup.

    I was excited about Lightpeak. A little less excited about Thunderbolt. Still waiting for something to happen. You pretty much sum it all up right here (bold added):

    Potential. Thunderbolt is relatively new and some day it MIGHT back up its promise. MIGHT. Already I am seeing articles about how PC manufacturers that initially embraced Thunderbolt are now removing them in new models.

    In any case, all this has been said before and it will all be said again, so mostly I don't know why we have to have yet another PCIe vs Thunderbolt thread full of the same arguments. I'm a little bit irritated that I got sucked in yet again.
  13. ABCDEF-Hex macrumors 6502


    Feb 15, 2013
    Very interesting:

    Please post again when that "new alternative" starts shipping.
  14. ABCDEF-Hex macrumors 6502


    Feb 15, 2013
    Oh, by the way:

    ASUS first to arrive with motherboard packing Intel's 20Gbps Thunderbolt 2
    By Steve Dent posted Aug 20th, 2013 at 3:43 AM (Engadget)
  15. goMac macrumors 603

    Apr 15, 2004
    The cards aren't meant to (and don't) run in Crossfire. One handles OpenCL while the other handles OpenGL, or they drive different displays. There are no known glitches in this config, even under current OS X versions.

    You should be able run them in Crossfire in Windows of course. But Mavericks isn't getting Crossfire support because that's not the point.
  16. ActionableMango macrumors G3


    Sep 21, 2010
    Theoretical alternative. Do I really have to explain that you? Apparently so.

    I'm not against Thunderbolt. I'm against the removal of SATA bays and PCIe with Thunderbolt as its replacement.

    I bet that ASUS motherboard has SATA connectors and PCIe slots.
  17. freejazz-man macrumors regular

    May 12, 2010
    It's boring when people come here and make their arguments, but DON'T actually respond to the OP.

    Why don't you respond to his actual point. He is saying thunderbolt isn't great now, but over the timeframe for the new mac pro, it is going to be the only way that Macs are going to see significant expandability action. Do you think that wont be the case? Why?
  18. deconstruct60 macrumors 604

    Mar 10, 2009
    Arrive???? Chuckle. Not.

    If actually look at the title of the Anantech's article this is based off of that is closer to the truth

    "World's first certified Thunderbolt v2 Motherboard".

    Both this motherboard and the Mac Pro 2013 are in the 'will show up later this year' status.

    Even the engadget article says so:
    " .. There's no pricing or availability yet, though Thunderbolt-equipped motherboards tend to be expensive. ... "

    from the Anandtech article:

    "... Here’s the short specifications summary for the Z87-Deluxe/Quad; we’re awaiting further details on expected availability and pricing, ..."

    Thunderbolt v2 controllers are not scheduled for volume production until 2014. That isn't speculation that what Intel has said about the rollout (a position they have stuck with for coming up on 2 years). There will be some in 2013, but the tech was not particularly targeted for 2013.

    The board is in far better shape than last year's Rube Goldberg Thunderbolt add-in-card in that it has actually passed certification. However, I don't think Thunderbolt v2 is really ready for prime time just yet. Given Intel using "packages just from the initial batches from fab" at the NAB demos a couple of months ago, it probably has another month or two of QA in front of it.
  19. goMac macrumors 603

    Apr 15, 2004
    As I mentioned in another thread, part of the reason there is a lack of Thunderbolt devices is because there is a lack of Thunderbolt on a lot of Macs. If you've been making devices meant for Mac Pro users, you've been forced to make PCI-E devices. That's not a judgement on Thunderbolt, that's the reality of the Mac Pro not shipping with Thunderbolt until now and only PCI-E.

    The complaining about the lack of Thunderbolt devices for the Mac Pro is silly. With the Mac Pro adopting Thunderbolt, they'll arrive. The comparing of the number of Thunderbolt devices vs. PCIe devices for the current Mac Pro is just dumb.
  20. ABCDEF-Hex macrumors 6502


    Feb 15, 2013
    I did not say it was shipping.

    Just wanted to reply to the poster who said the following without a source:

    "Already I am seeing articles about how PC manufacturers that initially embraced Thunderbolt are now removing them in new models."
  21. thekev macrumors 604


    Aug 5, 2010
    It wouldn't have been practical given the range of memory configurations and lack of necessity. So far they have only soldered when height was a factor.
  22. deconstruct60 macrumors 604

    Mar 10, 2009
    This is a skewed viewpoint of Thunderbolt that tends to send these Thunderbolt trade-off discussions down the drain. Thunderbolt is not just PCIe. It isn't intended to replace PCIe. It transports both Display Port and PCIe data traffic to external boxes. If throw out half of the capabilities, not going to see the value/utility of what it provides.

    Not just mobile. All-in-one and small-from-factor systems get more competitive also. In other words, the whole rest of the Mac line up that sells 10's of millions of systems per year.

    markplace of 10M/year or 100K/year which one is a bigger market? Even 10% of 10M/year, 1M/year vs. 100K/year which one is bigger?

    Only marginally getting in the game. Mainstream legacy PC motherboard and laptops are going in a different direction that Macs ( and some other parts of the PC market). Same price classes there will be some correlation between Macs and WinPCs thunderbolt adoption over time. However, were average selling prices are radically different there won't. The $300-450 box-with-slots market isn't going to adopt TB much even over the long term. Those are driven primarily about price and not performance.
    For different motivations but same net divergence. $4500-6000 systems are likely not going to adopt TB much either.

    With a renewed push to drive WinPCs cheaper, There will probably be a short term retreat by the "razor thin margin" system vendors from Thunderbolt. It isn't because Thunderbolt doesn't have utility, it is primarily because cheaper matters more than max performance.

    but there is a finite number of PCIe lanes upon which to provision slots. That is going to be a design limiter if not looking to massively oversubscribe inside the box. (i.e.., where do you put over-subscription. Inside where Apple only controls it. Outside, where the user controls it. )

    Technically, consuming a x16 socket and buying a PCIe expansion box this can be done. It is not particularly inexpensive. End up with similar bandwidth over-subscription issues that Thunderbolt has if try to push the externalized cards into maximum performance corner.

    Value add here goes past just only looking at PCIe.

    Technically the "box with slots" market isn't decline; yet. It is largely flat. There are folks in the market. The problem is there is just as many folks leaving (Lengthening upgrade cycles and switch wholly to used market is pragmatically leaving. That in addition to folks moving to different class of systems )it as coming in (or buying upgrades). The major problem is that actually look at the Personal Computer market ( not limited by legacy form factor view myopia ) the overall market is still growing. That's why the box-with-slot percentage is shrinking. It is because the general market is leaving.


    Not just height. Sub 0.8" height was a factor. It is a tradeoff because soldering is actually somewhat inefficient for large GB amounts in terms of horizontal space consumed. The Mac Pro blows both of those out of the water ( way past sub 1" and way past single digit GBs. ).
  23. ThisIsNotMe Suspended

    Aug 11, 2008
    Think the new Mac Pro simply illustrates Apple's belief that applications are moving away from proprietary 'accelerator' cards in favor of OpenCL.
  24. deconstruct60 macrumors 604

    Mar 10, 2009
    At least Acer is .

    Acer 2012
    "... Second, Thunderbolt arrives in the Windows ultrabook market at the end of the month with the 2.65-pound, $1,400 Acer Aspire S5. ... ";txt

    Acer 2013
    " ... , we've got more bad news: an Acer representative talking to CNET has said that the company has no plans to support Thunderbolt in its PCs this year. Acer's Aspire S5 Ultrabook was one of the few Windows laptops to include Thunderbolt support when it was introduced in early 2012. ..."

    the CNET article referenced there is a bit more balanced in pointing to drops and wins.

    Given Intel's target is higher end systems Acer dropping out isn't all that surprising. It really isn't what their core competency is. They have some higher end systems but the bulk of what they do is pushing average selling prices down.
  25. -hh macrumors 68020


    Jul 17, 2001
    NJ Highlands, Earth
    I've read VR's post and while I agree with certain aspects of its statements and observations, I do also agree with the contrarian view of how we are accepting a comparison to a 4 year old solution - - we can easily search the MR archives and find "New Mac Pro" discussions from 2009, 10, 12 which discussed the rumors of their day and what they expected the upgrade to have ... And the disappointments of when they failed to maintain parity with the PC market. From there, the flow down into "doesn't just work" for stuff like USB3 and SATA3 are more damning of Apple's negligence than anything else.

    As such, I really see much of the contemporary praise for the Tube as really being "Yay! They finally did *something* for us", where the customer expectations were so low it could have been as little as USB3 and SATA3 with the old CPU (figuratively speaking).

    However, I do also see and recognize that the traditional desktop PC box market is flat/decline, so some out-of-the-box effort is appropriate. But what this then hearkens is is TB the answer (enabler)? Well, the problem there is that uptake simply has been too expensive/slow and I'm really afraid that the outcome is going to be 'No'....

    ....but if the "Thunderbolt Tax" drops to a relatively minor* level by Christmas 2013, I'd be quite happy to be wrong. Time will tell.

    * - to commit to a specific prediction, I'll call this to be under $50 for a relevant peripheral...EG, a TB external drive costs the same as a USB3, except that it doesn't come with a TB cable (hence the $50 delta).


Share This Page