OlfinBedwere said:
It also had that 32MB of faster eSRAM which was intended to act as a fast cache and make up for the slower main memory bus. Which developers promptly stopped using as soon as the One X (which didn't include it and just kicked everything out to its faster main memory) arrived on the scene, explaining why the quality of One (S) ports of third-party games dropped off a cliff from around 2018 onwards. |
The eSRAM was a net-benefit, if a developer didn't optimize their games for it, it just acted like a cache for the GPU (For the CPU, it still needed to copy to DRAM first) automagically.
The eSRAM was mapped to a part of the system memory, so it was transparent, so developers could opt to make their stencil buffer, z-targets or more into that part of the memory space, but they didn't have to.
But even if Microsoft had 176GB/s of GDDR5 bandwidth like the Playstation 4, the eSRAM would still have been a big benefit, there is a very big reason why AMD includes upwards of 128MB SRAM in their GPU's -and- CPU's these days.
The issue isn't the eSRAM itself, the issue is that it's not a large overall encompassing cache that can communicate with the CPU and GPU concurrently like what would occur with Intel CPU/IGP's, that's a design choice on AMD/Microsofts part. And a silly one... Having to copy the CPU data to DRAM, then transfer it to eSRAM for the GPU to work on and vice-versa is not efficient, it's wasted cycles.
The real issue that held back the Xbox One was: System Memory, the DDR3 on a 256bit bus wasn't enough, it needed to be on a even wider bus to match GDDR5 or Microsoft needed to adopt GDDR5.
But there also wasn't a point in doing that unless Microsoft made a larger GPU, having only 16 ROPS (Render Output Pipeline) isn't going to make much use of memory bandwidth, it needed 32 ROPS, the Xbox One was ROP starved.
The lower amount of shader pipelines, texture mapping units and more were also a hindrance.
And this is where the crux of the issue is... Microsoft SACRIFICED compute resources for cache, Microsoft should have had a larger GPU, with faster DRAM, but kept the cache.
Large caches have been the reason for some of the largest improvements in performance and efficiency in the PC space over the last few years, it's definitely not a useless "feature".
As for the Xbox One X specifically... Microsoft still had the eSRAM mapped to a part of the system memory. - But if the Xbox One X included eSRAM and made those changes that I alluded to above... There would have been further performance and efficiency gains, the Jaguar cores were trash, more cache would let them breathe a little better, but alas, that was not a design choice Microsoft had in mind when developing the Xbox One platform.
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