Next 13" MacBook Pro Design Analysis

It seems that some are still holding to the belief that Apple can't add a discrete graphics processor to the 13" MacBook Pro simply because there is no room in the current form factor to do so. In the following posts I will provide some arguments to challenge that opinion. This discussion could prove useful even after the introduction of Apple's next generation MacBook Pros, since I'm sure there will still be lots of questions and "why nots" about the final designs.

Let's start by looking at the chip package area to estimate how much room would be required on a motherboard to include a given chip set (CPU, system controller, and GPU). There are, of course, other factors such as the package landing area used for the routing of connections to the chip and the requirements for cooling, but I'm going to propose that the total package area is an important enough consideration to provide a guesstimate to answer the question, "Would a discrete GPU fit?". In any case, the available area on a given motherboard design is something that can be optimized though other changes -- more highly integrated support chips, smaller, more efficient battery, or better cooling mechanisms, etc. Thus, it's probably reasonable to assume that the motherboard layout and space utilization on the existing 13" MacBook Pro could be improved upon and therefore past designs can only be used as a rough and somewhat dated guide to what might be possible today (or this coming Thursday).

First, the simple "tale of the tape" (and our benchmark for further comparison):

Total chip package area for Core 2 Duo CPU and NVIDIA 9400M system controller/GPU as used in the original unibody 13" MacBook Pro: 2380 mm2

Note, the above values are based on the chip package sizes (that part which is actually mounted to the motherboard). The actual chip die sizes are MUCH smaller and while the die size is pretty much irrelevant to this discussion, I want to stress that the values I'm using are for the full chip package, not the smaller die size.

The reason I have decided to use the previous generation 13" MacBook Pro design as a benchmark is that I can't find much information on either the size or thermal properties of NVIDIA's 320M system controller/GPU that is used in Apple's current 13" systems. Besides that, I have seen posts that have referenced an analysis of the original 13" MacBook Pro done by Ars Technica as an argument that there simply isn't room in the existing 13" design to include a discrete GPU (whether true or not, but here is a link to that Ars Technica analysis: http://arstechnica.com/apple/news/2010/04/why-the-13-macbook-pro-didnt-get-a-core-i5-upgrade.ars ).

Now, for an estimate on the total chip package area on a hypothetical Sandy Bridge-based system with a discrete GPU (three packages or chips, the CPU, the Intel System Hub, and the discrete GPU): 2150 mm2

As you can see, based purely on chip package size there appears to be room to include a Sandy Bridge CPU, the Intel System Hub, and a discrete GPU (the latter with the same package size as the NVIDIA GT 330M GPU used in the 15" Mac Book Pro -- which is a rather generous estimate). It is also worth noting that Intel's System Hub controller does NOT require a heat sink (you can confirm that by looking at the existing 15" MacBook Pro design which contains only two heat sinks, one for the CPU and another for the discrete GPU). Furthermore, the original 13" MacBook Pro also had two heat sinks, one for the CPU and one for the NVIDIA 9400M system controller/GPU.

IMO, there seem to be two possibilities for the next 13" MacBook Pro.

Sandy Bridge CPU (pretty much a given) + Intel System Hub: 1370 mm2 chip package area with ONE heat sink for the CPU.
-- or --
Sandy Bridge CPU + Intel System Hub + discrete GPU: 2150 mm2 chip package area estimate with TWO heat sinks (one for the CPU, one for the discrete GPU).

And, once again our "benchmark" Core 2 Duo design with the NVIDIA 9400M: 2380 mm2 with TWO heat sinks (one for the CPU, one for the controller/GPU).

In case you are wondering, here is a list of the sizes of each chip package (largest to smallest).

Core 2 Duo CPU: 35 mm x 35 mm = 1225 mm2
NVIDIA 9400M system controller/GPU: 34 mm x 34 mm = 1156 mm2*
NVIDIA GT 330M discrete GPU: 28 mm x 28 mm = 784 mm2*
Sandy Bridge dual-core mobile CPU: 31 mm x 24 mm = 744 mm2
Intel System Hub: 25 mm x 25 mm = 625 mm2

*the package sizes on the 9400M and GT 330M were estimated from high-resolution photos, the other values are from Intel's website.

Note the trend, the Core 2 Duo and the NVIDIA 9400M packages are huge in comparison to the latest chip sets.

Now, the only questions remaining are chip costs and the heat dissipation requirements which I plan on covering in a follow-up post.

Total system cost is a factor and here we encounter some problems. First, we don't really know what Apple pays for chip sets and Intel has been rather spotty in offering estimated prices for the new Sandy Bridge processors (for some configurations). The same problems exist for the discrete GPU. Thus, the best I can do is to make a SWAG (Simple Wild-Ass Guess) and suggest that a new 13" MacBook Pro with a discrete GPU would retail for about $1499 ($300 more than the current base price in the U.S.).

Most of this price increase comes from my expectation that Apple would have to use a higher-priced, low-TDP (Thermal Design Power) Core i7/i5 processor for the 13" MacBook Pro's compact form factor. There is only one low-TDP Sandy Bridge Core i5 that Intel has announced (the i5-2537M) and it might be an option, but it runs at CPU clock speeds (turbo modes) that range between 1.4GHz to 2.3GHz which might not benchmark very well against the existing Core 2 Duo systems (which are non-turbo and currently offered by Apple at two speeds: 2.4GHz and 2.66GHz).

You might then ask, why can't Apple just use a standard Sandy Bridge Core i5/i3? IMO, it's simply a question of heat dissipation. Intel's standard, dual-core, mobile Core-i processors run at 35W, which is 10W higher than the Core 2 Duo used in the current 13" MacBook Pro. I suspect that the only reason why Apple can use the "hotter" Core i7/i5 chips in the 15" and 17" MacBook Pro designs is because those models have room for TWO rather large cooling fans. The 13" MacBook has room for only one fan, thus in my hypothetical design I've chosen to keep the total heat dissipation close to the previous 13" designs.

Below are my thermal dissipation estimates for the original 13" MacBook Pro:

Core 2 Duo CPU (25W TDP) + NVIDIA 9400M system controller/GPU (12W) = 37W total*.

*The 12 watt value for the NVIDIA 9400M is based upon estimates that I've found on the internet, as I've been unable to find detailed specs on either chip package size or thermal requirements for NVIDIA chip sets.

Note that Apple could easily use a standard Core i3/i5 at a 35W TDP if they don't include a discrete GPU.

For a hypothetical re-design on the 13" MacBook Pro I'm going to introduce two more assumptions. The power dissipation for the Intel System Hub will be ignored since it is only a few watts and doesn't require a heat sink (thus, the single-fan cooling system in the 13" MacBook Pro will only be "burdened" by the CPU and GPU). Second, I'll estimate that the discrete GPU will dissipate 17 watts (I think an overly high value which is based upon what I've found for the NVIDIA GT 330M). As for the latter, I suspect that Apple could do better, I'm sure that some of the newer mobile GPUs draw less power while still easily exceeding the performance of the integrated GPU used in the current MacBooks.

So, let's review some of the possible candidates for the Sandy Bridge CPU (with their corresponding range in turbo clock speeds and thermal requirements in watts, values under 35W are higher-priced, low-TDP parts which may be in short supply):

Core i7s
2617M (1.5/2.3/2.6GHz @ 17W TDP)
2657M (1.6/2.4/2.7GHz @ 17W TDP)
2629M (2.1/3.0GHz @ 25W TDP)
2649M (2.3/3.2GHz @ 25W TDP)

Core i5s
2537M (1.4/2.0/2.3GHz @ 17W TDP)
** there appears to be no 25W TDP Core i5 currently offered by Intel, I'd estimate that such a processor might operate within a turbo range of 2.0/2.7GHz **
2520M (2.5/3.2GHz @ 35W TDP)

Now, combine the above thermal requirements with our previous and rather generous assumption for a discrete GPU:

Core i5-2520M (35W TDP) + GPU (17W) = 52W total (not likely, given the single-fan design in the existing 13" MacBook Pro).
Core i7-2629M or i7-2649M (25W TDP) + GPU (17W) = 42W total.
Core i7-2617M or i5-2537M (17W TDP) + GPU (17W) = 34W total.

And, once again our "benchmark" design: Core 2 Duo (25W TDP) + NVIDIA 9400M (12W) = 37W total.

Given all of the above, I think it's possible that Apple could combine a low-TDP Sandy Bridge CPU with a discrete GPU to produce a fairly attractive 13" MacBook Pro design. It will, however, cost you and I'm not certain that Intel's existing low-TDP Core i5 will benchmark that well against the Core 2 Duos. Another option being that Apple could use one of the Core i7s, which would seem pretty strange given that the 13" MacBook Pro is currently marketed -- or seen -- as Apple's low-end pro model.

There are, however, some additional caveats. I've had to estimate the power requirements for the NVIDIA parts since I can find no direct specs or references from NVIDIA itself. The numbers I used came from technical sources on the internet (e.g. http://www.notebookcheck.net and others). If anyone has more reliable sources or figures, please posts those so that I can update my calculations.

Next, I'm not certain that Apple would or could use a low-TDP Core i7/i5 in a redesigned MacBook Pro. The cost is a big factor (of course), but it is also possible that Intel could have some objection to trying to produce additional low-TDP parts to meet the increased demand that might result from a new MacBook Pro design. It might mean only one or two million additional units per quarter for this class of processor but it seems obvious to me that Intel does not consider these low-TDP CPUs to be among their standard or mainstream offerings (it's a case of supply-and-demand and the costs associated with a CPU that may be difficult to manufacture).

On the plus side, it's very likely that Apple could find a better choice for a discrete GPU than the NVIDIA GT 330M I used for my analysis. They might use a smaller, lower-TDP, discrete GPU that could still notably outperform Sandy Bridge's integrated GPU without breaking the thermal budget on the 13" MacBook Pro design. Of course, such an option would have to offer enough value over Sandy Bridge's integrated GPU to negate the likely increase in system cost, since some consumers would balk at paying anything more than the current $1199 base price. It may, after all, be simply a matter of price and not a technical limitation or something directly to do with the 13" MacBook Pro's form factor.

macdud said:

...my humble guess: standard i3/i5 with no discrete gpu...

Click to expand...

After doing my analysis I'd have to agree, the 13" MacBook Pro probably won't be getting a discrete GPU. Largely because of the costs associated with the low-voltage/low-TDP Sandy Bridge processors. Furthermore, since Intel isn't offering a 25W TDP Core i5 I really can't see Apple stepping up and using a low-voltage Core i7 at the bottom of the MacBook Pro line.

So, this means the excited complaints about Intel's integrated graphics will probably dominate all discussion about the new 13" MacBook Pros.

What worries me now, however, are the rumors that the 13" MacBook Pro will use a Core i3 processor. That means a modestly clocked, fixed frequency part with no Turbo Boost mode. The only justification I can think of for using such a "cheap" processor in a product with a "Pro" designation is that the price savings will be applied to some other feature, perhaps the rumored 16GB SSD system cache. I guess that might be okay as long as they hold the price at the current $1199.

definitive said:

...apple really needs to stop slacking, and making excuses for their 13" laptops, and start catching up to their competitors who can offer better hardware for same or lower price (yes, im aware of "but it looks bettar" and "i have moar battery lief").

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I think if you read my analysis you would see that Apple doesn't have to make any excuses. The reason why the 13" MacBook Pro may ship without a discrete GPU is that Intel still isn't offering a 25W Core-i processor that would be a good fit in Apple's current MacBook Pro lineup. It may be that Apple is still trying to hit a starting price point of $1199 for the entry-level MacBook Pros (assuming no other changes for the better, which could justify a higher price).

Yes, Apple does charge more for the equivalent raw performance, but they can do that because their customers see additional value in other areas (some of which is real and some arguably imaginary).

dnkbro said:

One thing to keep in mind is Open CL support. Intel has been lagging with Open CL support for Sandy Bridge's IGP. Lion will use Open CL and it's coming this summer. Apple isn't going to release a laptop without discrete graphics if it doesn't support their software. I think at worst the new 13" MacBook Pros get the 320M from last year's refresh.

Click to expand...

I guess you mean the NVIDIA GT 320M, since the current 13" MacBook uses NVIDIA's 320M system controller/GPU which can't be used with the Sandy Bridge processor, that's one reason why last year's refresh stuck with the Core 2 Duo.

As for OpenCL, that's an abstraction layer (in software) that can be adapted to different underlying hardware. It may not run as fast when based on Intel's integrated graphics and the Sandy Bridge core but it will still function.

dnkbro said:

...What's stopping Apple from having Nvidia or ATI make a card specific for their MacBook Pro again?

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Nothing, except it would have to be a discrete GPU not an integrated system controller/GPU as with the previous generation's NVIDIA 9400M and 320M.

Besides that, I assume that you are talking about the 13" MacBook Pro and if so I think I've already answered your question (at length) in the original two posts that started this thread. Apple could design a 13" MacBook with a discrete GPU but it would raise the price of the entry-level model and most likely it would require a low-TDP/low-voltage Core-i processor which wouldn't perform as well as the mainstream Sandy Bridge processors (i.e. those CPUs running at a full 35W TDP).

icebiker said:

...Since there's only 1 core i3 mobile processor would it be possible to use it for both low end and high end 13" ?

If so...what would be upgraded to justify a price differenceof 300 $ ?

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An upgrade to the Core i5? That would be a little unusual, but it would be better than Apple's typical small bump in clock speed and hard drive space. Frankly, I don't see why they couldn't use the Core i5 in all of the MacBook Pros (including the 13" model).

icebiker said:

Let's not forget that from a marketing point of view Apple cannot offer a 13" with a SB i7 (even if it is a LV) and the 15" with a SB i5...

Then there's the price, the i7 LV just costs too much, and Apple is interested in high margins...

Click to expand...

Well, yes, that's what I said in my original analysis.

fpnc said:

It will, however, cost you and I'm not certain that Intel's existing low-TDP Core i5 will benchmark that well against the Core 2 Duos. Another option being that Apple could use one of the Core i7s, which would seem pretty strange given that the 13" MacBook Pro is currently marketed -- or seen -- as Apple's low-end pro model.

Click to expand...