Hot Chips 2020 Live Blog: Microsoft Xbox Series X System Architecture (6:00pm PT)
by Dr. Ian Cutress on August 17, 2020 9:00 PM EST- Posted in
- CPUs
- Microsoft
- GPUs
- Xbox
- Live Blog
- Xbox Series X
- Hot Chips 32
09:04PM EDT - Final talk of the day is Xbox Series X System Architecture!
09:05PM EDT - Azure Silicon Architecture Team
09:06PM EDT - 3.8 GHz Zen2 Server cores
09:06PM EDT - DXR, VRS, Machine LEarning Acceleration
09:07PM EDT - 14 Gbps GDDR6, 320-bit = 560 GB/s
09:07PM EDT - Hardware accelerators in blue
09:07PM EDT - 120 Hz support, VRR, Xbox Velocity Architecture for MSP Crypto/Decomp on NVMe SSD
09:07PM EDT - Acoustic acceleration
09:07PM EDT - HSP/Pluton RoT - security
09:08PM EDT - 360.4mm2 TSMC N7 enhanced
09:08PM EDT - 15.3B transistors
09:08PM EDT - 2 four core CPU clusters
09:08PM EDT - 10 GDDR6 controllers
09:09PM EDT - GPU 12 FLOPs
09:10PM EDT - AVX256 gives 972 GFLOP over CPU
09:10PM EDT - 16 GB of GDDR6 total
09:11PM EDT - >Says Zen2 server class, but L3 cache is mobile class?
09:11PM EDT - Display processing is kept off the shader engines
09:11PM EDT - IO hub supports PCIe 4.0 x8
09:11PM EDT - Operates on linear light values, not gamma light values
09:12PM EDT - ALLM - Auto Low Latency Mode
09:13PM EDT - Increased die cost on this APU over previous generation
09:13PM EDT - Significantly more expensive!
09:13PM EDT - Trade off
09:13PM EDT - MS created Audio engines - 3 engines, CFPU2, MOVAD, LOGAN
09:13PM EDT - CFPU2 for audio convolution, FFT, reverb
09:14PM EDT - such as Project Acoustics to model 3D audio sources
09:14PM EDT - MOVAD - hyper real-time hardware audio decoder
09:14PM EDT - >300x channels decode at once
09:14PM EDT - best trade off codec, so made in hardware
09:15PM EDT - >100dB signal noise ratio
09:15PM EDT - HW realtime real-time matched to decode based on sampling
09:15PM EDT - Logan is offering also better offload in traditional modes
09:15PM EDT - HSP/Pluton: Root of trust, crypto, SHACK (crypto keys)
09:15PM EDT - MSP supports 5 GB/s high-bw crypto on the SSD
09:16PM EDT - DRAM to SSD balance needed for refill
09:16PM EDT - Load times are always increasing unless SW-to-DRAM bw increases, hence NVMe SSDs
09:17PM EDT - Sampler Feedback System
09:17PM EDT - New metadata for texture portions to pre-load texture caches
09:17PM EDT - Direct Storage
09:17PM EDT - Manages data locations ahead of developer
09:18PM EDT - Distinct savings for most detail texture maps savings
09:18PM EDT - Lossless MS XVA 2:1 compression
09:19PM EDT - Need big GPU - get the tech out of the way
09:19PM EDT - Need raw ops/second increase within PPA and cost
09:19PM EDT - 12.2 supported in HW
09:19PM EDT - 26 active dual CUs (52 CUs)
09:20PM EDT - single geometry supports primatives
09:20PM EDT - DIrectly snoop CPU caches
09:20PM EDT - Dual stream multi-core command processor
09:20PM EDT - Double rate 16-bit math
09:20PM EDT - single cycle issue rate to reduce stalls
09:21PM EDT - CUs have 25% better perf/clock compared to last gen
09:21PM EDT - GPU Evolution: FLOPS have outpaced mem space and BW
09:21PM EDT - Screen pixels has increased in th emiddle
09:22PM EDT - How to fill pixels better without blowing power budget
09:22PM EDT - VRS
09:22PM EDT - supports up to 2x2
09:22PM EDT - 10-30% perf gain for tiny area cost
09:23PM EDT - Full edge detail
09:23PM EDT - SFS
09:24PM EDT - Previously very slow to enable
09:24PM EDT - Two new HW structures for tile-by-tile management for in-DRAM textures
09:25PM EDT - clamps LOD
09:26PM EDT - Tilemaps should stay on die for best latency
09:27PM EDT - SFS: 60% IO/Mem savings for small die area cost
09:27PM EDT - DX Ray Tracing Accel
09:27PM EDT - Not a complete replacement - RT can be applied selectively based on traditional models
09:28PM EDT - Custom ray-triangle units
09:28PM EDT - ML inference
09:29PM EDT - Two virtualized command streams - two VMs
09:29PM EDT - Main title OS vs system OS
09:29PM EDT - 32b HDR rendering, blending display
09:29PM EDT - Optimized games. Unable to show at the event
09:30PM EDT - Q&A Time
09:31PM EDT - Q: TDP? A: Not commenting. There's so many things that are involved in the TDP, and tradeoffs. We're not really able to descibe it without describing it in a technical environemtn
09:32PM EDT - Q: Can you stream into the GPU cache? A: Lots of programmable cache modes. Streaming modes, bypass modes, coherence modes.
09:33PM EDT - Q: Coherency CPU and GPU? A: GPU can snoop CPU, reverse requires software
09:35PM EDT - Q: Are you happy as DX12 as a low hardware API? A: DX12 is very versatile - we have some Xbox specific enhancements that power developers can use. But we try to have consistency between Xbox and PC. Divergence isn't that good. But we work with developers when designing these chips so that their needs are met. Not heard many complains so far (as a silicon person!). We have a SMASH driver model. The games on the binaries implement the hardware layed out data that the GPU eats directly - it's not a HAL layer abstraction. MS also re-writes the driver and smashes it together, we replace that and the firmware in the GPU. It's significantly more efficient than the PC.
09:35PM EDT - Q: Is link between CPU and GPU clocks? A: Hardware is independent.
09:36PM EDT - Q: Is the CPU 3.8 GHz clock a continual or turbo? A: Continual.
09:36PM EDT - Continual to minimize variance
09:37PM EDT - Q: TSMC 7nm enhanced, is it N7P, N7+, or something else? A: It's not base 7nm, it's progressed over time. Lots of work between AMD and TSMC to hit our targets and what we needed
09:38PM EDT - Q: Says Zen 2 is server class, but you use L3 mobile class? A: Yeah our caches are different, but I won't say any more, that's more AMD.
09:39PM EDT - Q: With 20 channels GDDR6, is that really cheaper than 2 stacks HBM? A: We're not religious about which DRAM tech to use. We needed the GPU to have a ton of bandwidth. Lots of channels allows for low latency requests to be serviced. HBM did have an MLC model thought about, but people voted with their feet and JEDEC decided not to go with it.
09:40PM EDT - Q: GDDR6 on sides, not bottom? A: bottom is power, how board interfaces with the chip. GPU has high EDC and currents, and you need clean copper to deliver that. With that much current you need to leave that space unless you use super expensive packaging. We did it the cost efficient way
09:41PM EDT - Q: Why do you need so much math for audio processing? A: 3D positional audio and spatial audio and real world spaces if you 300-400 audio sounds positional in 3D and want to start doing other effects on all samples, it gets very heavy compute. Imagine 20 people fighting in a cave and reflections with all sorts of noises
09:43PM EDT - That's a wrap and we're done for today. Come back tomorrow at 8:30am PT to talk about FPGAs. It's 2:44am here in the UK, time to go to bed.
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Raqia - Tuesday, August 18, 2020 - link
This would be a very attractive APU for a gaming PC. It's a shame that the integrated design of consoles with one big and fast pool of memory isn't copied PC designs with open application installation, and enthusiasts are still left with only legacy architectures with DIMMs and a GPU sitting across at PCIe bus with its own separate pool of memory. Yes, you get upgrade options and the opportunity to swap in snapshots of the state of the art GPU once in a while, but the integration really does improve efficiency, and the snapshots will matter less as process improvements slow. Furthermore, the cost of the entire console is way less than a high end GPU as well.Microsoft can afford a custom design like this because it gets subsidized by licensing in the end; it would be great if it licensed up the APU for implementations by other OEMs like something meant to work with Valve's Steam for instance.
drothgery - Tuesday, August 18, 2020 - link
GDDR has significantly more latency than DDR, which usually isn't a good trade-off for a general purpose computer. For gaming and streaming, it's a different story.Raqia - Tuesday, August 18, 2020 - link
That's a fair point, and I wouldn't use this to run something like a DB server. However, I wouldn't provision a GPU like this for a server chip either and something architected like this would still run productivity apps just fine.I think it makes perfect sense to redefine the "unit of upgrade" abstraction for an entertainment oriented PC along similar same lines as a console, bundling a CPU and RAM upgrade along with a GPU upgrade which would give you more performance for the buck now that high end GPUs retail for > $1k. You can keep separate your storage, power supply, and PCIe cards just like before and keep apace with any innovations from the console space as well.
vithrell - Friday, August 21, 2020 - link
That architecture would require support in Windows/Linux drivers, there was Chinese PC-Console called Subor Z+ with custom APU based on quad core zen and ~1500 SP iGPU coupled with GDDR6 memory and it had compatibility issues. People also ran Linux on PS4 and PS4 Pro, and there 8 small CPU cores were the problem.eastcoast_pete - Tuesday, August 18, 2020 - link
After re-reading the parts about the audio processing, here is how I translated it for myself: " we wanted to get Dolby Atmos-like audio, but really wanted to avoid paying license fees for console and games. So, we came up with this".eastcoast_pete - Tuesday, August 18, 2020 - link
Also, found it interesting that they emphasized the AVX256 prowess of their CPU cores. I guess upcoming games will make use of that; the numbers are impressive. Alternatively, is this about using the chip in Azure xCloud?abufrejoval - Thursday, August 20, 2020 - link
Looks like really nice hardware!Now if they only gave up on trying to suck people into the Microsoft store...
I want to be able to buy a game on Steam and then play it on any of my various PCs, in the cloud when I am on the road (e.g. Nvidia Geforce Now) or on an Xbox (even a PSx for that matter).
The hassle of being locked into distinct eco-systems for every device is just blocking sales.
Ptosio - Monday, August 24, 2020 - link
Can it run WIndows?It has a decent PC-class hardware - if Microsoft really cares about reducing electrowaste and carbon footprint it should allow tro run Windows-on_Xbox so that people would not be forced to buy extra desktop containing essentially the same basic parts.