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prism

macrumors 65816
Original poster
Dec 6, 2006
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ok so it seems to be a given that the skylake 13 rMBP will come with the 550 igpu. From what I've read it is essentially the exact same architecture as the broadwell 6100 except that it comes with a 64mb memory cache that substantially boosts the performance (in the order of something like 50%), is this correct that the only difference is the cache and just having that can so substantially improve performance?
 
I'm interested in this as well as I don't know if I can hold out to September if it comes to it for the 13". I want to do some light gaming and I haven't fully understood how significant the 550 is compared to the 6100.
 
ok so it seems to be a given that the skylake 13 rMBP will come with the 550 igpu. From what I've read it is essentially the exact same architecture as the broadwell 6100 except that it comes with a 64mb memory cache that substantially boosts the performance (in the order of something like 50%), is this correct that the only difference is the cache and just having that can so substantially improve performance?

Pretty much yes that's exactly what the original Iris pro did on the i7 quad core mobile processors added a 128mb eDRAM cache and it was a huge boost.
 
Yes, from the benchmarks I've seen the boost from the HD 6000 to the Iris 540 (the 15w versions of the 6100 and 550) is close to 50% so I would expect a similar boost for the 28w equivalents.
 
Honestly, Id expect certain applications to get more than 50%.

For Integrated GPU's, there are two main performance limiters - TDP and Memory bandwidth. The 64MB of localized ram really helps minimize memory bandwidth issues.
 
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Any idea if the i5 and the i7 Skylake chips will have much of a performance difference for gaming on the 13"?

Id expect gaming to be mostly a wash between the two. With the CPU fighting against the iGPU for its TDP limit id honestly expect both CPU's to be largely identical.
 
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The 550 should do much better in games and application that require high throughout, as Intel has rebalanced the sampler/ALU ratios. Also, if I remember correctly Skylake supports half-precision computation, which could give it a healthy boost in apps for which fp16 is enough. Overall, I'd expect about 30% increase in performance, more if we are talking about bandwidth-limited operations (where the new cache will play a big role).
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Any idea if the i5 and the i7 Skylake chips will have much of a performance difference for gaming on the 13"?

The i7 is often clocked higher, but given the thermal constraints, I doubt it would make much of a difference.
 
The 550 should do much better in games and application that require high throughout, as Intel has rebalanced the sampler/ALU ratios. Also, if I remember correctly Skylake supports half-precision computation, which could give it a healthy boost in apps for which fp16 is enough. Overall, I'd expect about 30% increase in performance, more if we are talking about bandwidth-limited operations (where the new cache will play a big role).

So just by adding a memory cache and keeping the rest of the architecture identical we get around a 30% boost? Makes you wonder why Intel didn't just include the cache in the first place!
 
So just by adding a memory cache and keeping the rest of the architecture identical we get around a 30% boost? Makes you wonder why Intel didn't just include the cache in the first place!

The rest of the architecture is by no means identical. There are a lot of changes and efficiency improvements. I guess they didn't add the cache earlier as not to make the chips prohibitively expensive (they were probably still working out the kinks of the tech).
 
So just by adding a memory cache and keeping the rest of the architecture identical we get around a 30% boost? Makes you wonder why Intel didn't just include the cache in the first place!

engineering issues I'd imagine. And of course haswell and broadwell did get it in the 4 core Iris pro chips but they are much bigger dies with increased thermal limits.
 
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