Though the same memory serves on-die graphics, 3DMark 11 actually suggests that CPU-heavy tasks gain most from increased DRAM data rates.

I began 3DMark Professional Edition testing with the app's low-end Ice Storm test, only to have a "what the...?" moment after switching over to integrated graphics. Looking for performance differences attributable to memory, I was stunned to see just how badly Intel gimped the GPU on its LGA 1150-based processor compared to the embedded version. We told Intel this before Haswell launched, but I believe the company underestimated the market for a socketed processor with Iris Pro graphics 5200.

Cloud Gate pulls the Core i7-4770K's HD Graphics 4600 into the low 20s, while the embedded CPU's Iris Pro graphics 5200 engine cruises through unscathed. Again we see only minor performance differences attributable to memory data rate.

- Did You Know Mobile Haswell Doesn't Support 1.5 V DDR3?
- Ripjaws DDR3-1866 Low Voltage
- Ripjaws DDR3-1600 Low Voltage
- G.Skill Standard DDR3-1333
- Test Hardware And Software Configurations
- Results: SiSoftware Sandra
- Results: 3DMark
- Results: 3D Games
- Results: Adobe Creative Suite
- Results: File Compression
- Power, Efficiency, And Final Thoughts
The R version has 128MB of L4 cache. At 1280x720, it is large enough for all index and vertex buffers and most textures. That is why main memory speed doesn't significantly affect Iris Pro 5200...
intel claims that the edram costs around $80. that'd jack the a10 6800k price over $200 only to benefit the igpu (possibly the same with gddr5). imo, the weaker cpu cores wouldn't benefit much, if at all. that'd make the apus of poor value and people will argue against the apus claiming you can have a faster configuration under $200 (e.g. core i3 4110/fx6300 + radeon 7770/7750) without requiring the edram. as for core i7 4770R (and other R skus) - it's way too expensive. afaik, brix pro is barebones, the whole pc might cost near $800-1000 fully configured.
Simply wait for Broadwell-K near the end of this year and you will get the option of buying a $300+ i5 or $400+ i7 with 128MB L4 cache and Iris Pro.
From what little info leaked about it so far, it is still unclear whether or not there will be an option to buy a desktop Broadwell without that ~$100 extra.