Core i7 5775C processor review: Desktop Broadwell

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The GT3e GPU Architecture

The integrated Iris Pro GT3e graphics engine

The IGP inside the processor is called the Intel Graphics Media Accelerator HD, and is derived from existing Intel graphics products, but has some nice new improvements. The embedded graphics core is an updated model though revamped, improved and definitely more powerful with an improved video en/decoder now as well. The Intel 5000 series integrated graphics core is incorporated onto the same die as the CPU, and it also has access to Intel's automatic overclocking Turbo Boost features.

The biggest change is a strong increase in IGP performance as Intel decided to embed the GT3e IGP. That pretty much boils down to the fact that this IGP has 48 EU's (GPU cores). Next to that within the processor package they have tucked an 128 MB eDRAM chip that functions as L4 graphics memory. It is the the GPU that will benefit here the most as it will be used as a fast buffer, opposed to using the relatively slow system memory. As example, Haswell processors have up-to 20 EU's, so the performance should be double compared to the previous generation iGPUs. For Broadwell the minimum number used in the lower end SKUs are 24 EU's thus running up-to 48 units for the high end GT3e model as used in today's tested processor. The EUs are arranged in sets of 8 modules. The iGPU is now compatible with DirectX 11.2 en DirectX 12 feature level 11_1, OpenGL 4.3 and OpenCL 2.0

The Quick Sync video encoder has had a speed bump as well and according to Intel, now offers better quality. For those interested, a HEVC hardware decoding support is not embedded. Intel however has a nice workaround, as the drivers support a hybrid decoder that makes use of both the CPU and GPGPU algorithms. Ultra HD screens are supported up-to 60Hz through DisplayPort 1.2, HDMI 2.0 unfortunately is not supported and thus an Ultra HDTV can't be used in 60Hz. Broadwell has a very interesting and capable GPU, gaming wise you can expect entry-level dedicated graphics performance but we like to see the unit more as a video processor. Very good for stuff like Blu-ray playback and it supports 3D playback thanks to HDMI 1.4a implementation, but not 2.0. It supports Intel Wireless Display (WIDI), will use the embedded DisplayPort standard to connect the GPU to the screen, and is capable of handling the task of transcoding video. 

128MB eDRAM L4 cache chip

Interesting for the two desktop processors that are released is not only that IGP, and also the embedded 128MB eDRAM cache. The 5775C & 5675C both have a Crystall Well eDRAM embedded DRAM silicon. This unit functions as an L4 cache and bridges the gap in-between CPU, GPU and system memory. From what we've learned, the chip runs internally at roughly 1600 MHz with a bi-directional throughput of 50 GB/s. Considering that dual-channel DRAM DDR3-1600 offers roughly 25 GB/sec that boils down to a much faster cache, especially if you take low latency of this on-die embedded cache into account. The 128MB eDRAM is as stated also available to the CPU and in theory could be used for typical CPU-workloads. 



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