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The lead APU of each generation usually wouldn't get meaningfully faster if you just spent more silicon on the GPU instead of the CPU. The fundamental problem

The lead APU of each generation usually wouldn't get meaningfully faster if you just spent more silicon on the GPU instead of the CPU. The fundamental problem here is that GPUs require more memory bandwidth than CPUs, the platforms are created for CPUs, resulting in a pretty hard cap on APU GPU performance using the same platform. Generational GPU performance gains on APUs happen when the platforms update to faster memory. The big break in this will be Strix Halo, coming from AMD either next year or late this year, as it will support 256-bit LPDDR5. Even using the fastest LPDDR5 available on the market, this will still just barely match the memory performance of Radeon 7600, the weakest current-gen discrete GPU AMD has on the market.

rowanG077 3y ago
And even then memory channels is not really a marketable term for OEMs so not much is done to get that in. Only enthusiast (and thus really expensive) laptops go with a large number of memory channels.
- wtallis 3y ago
  There aren't any enthusiast laptops with more than a 128bit memory bus for the CPU, and memory channels and bus width are the wrong metrics to compare discrete GPUs where both width and clock speed vary widely across the entire product line.
  - rowanG077 3y ago
    This isn't at all about discrete GPUs, where did you get that from? This is about APU/iGPUs. In general memory channel are expensive so you won't see a new product with 8 channels running 3000Mhz memory speed or something like that. Also Apple laptops do have large memory busses. The Apple M1 Max chip for example has a 512bit memory bus.
    - wtallis 3y ago
      I assumed when you said "Only enthusiast laptops go with a large number of memory channels" you intended to refer to something beyond just the MacBook Pro, because "enthusiast laptop" is usually used to describe a category that definitely includes a lot of laptops that aren't MacBook Pros, and only arguably includes some MacBook Pros. And if you did mean to refer specifically and only to MacBook Pros, there were plenty of more straightforward ways for you to do so.
      - rowanG077 3y ago
        It's quite simple really. Macbook Pro M1 Max is in the set of enthusiast laptops. You said there are none. I gave that as a counterexample. I wasn't specifically thinking about it in my original comment. In fact I wasn't specifically thinking about even a bus width that I consider "large". It was a general comment that memory channels are not cheap to have in a piece of silicon and that consumers generally don't care about it as a metric of performance.
jorvi 3y ago
I don’t know if this goes for VRAM, but I know that with system RAM, applications care very little about data rate and very much about timings. This includes games. I do know that overclocking VRAM (or at least GDDR6) barely increases performance, but that’s mostly because it’s usually already been pushed to the edge at stock. My old 3070Ti could easily overclock 10-15% higher, but the memory had to self-correct significantly more errors so the actual improvement was a wash. I’m also curious if gaming handhelds would benefit from switching their entire memory architecture over to VRAM, like both consoles have done in this generation.
- ben-schaaf 3y ago
  Timings are much less important for GPUs than bandwidth; the cores are slow and doing the same work on similar memory. A 3090 has ~270ns of memory latency - <70ns is normal for a CPU. See https://chipsandcheese.com/2021/05/13/gpu-memory-latencys-impact-and-updated-test/ https://chipsandcheese.com/2021/05/13/gpu-memory-latencys-im...
  - jorvi 3y ago
    Maybe I’m misunderstanding the article, but there’s multiple places where they mention memory latency being the main bottleneck. At any rate, thanks for sharing! Interesting stuff.
    - lynguist 3y ago
      No, it’s really bandwidth. Big GPUs have on the order of 800 GB/s memory bandwidth and big CPUs only 80 GB/s! Except for Apple. They really need to up the bandwidth. GPU performance is proportional to both bandwidth and compute.
AnthonyMouse 3y ago
> The big break in this will be Strix Halo, coming from AMD either next year or late this year, as it will support 256-bit LPDDR5. Even using the fastest LPDDR5 available on the market, this will still just barely match the memory performance of Radeon 7600, the weakest current-gen discrete GPU AMD has on the market. You can do better than that simply by putting some HBM or GDDR6 on the APU itself. Then you don't need to change the socket or have to add memory channels, and you don't need that much of it because you still have the ordinary memory slots to provide some DDR5 where the OS can keep all its dreck bloat. 8-16GB of the stuff would be enough to rival any of the current midrange discrete GPUs.
DinaCoder99 3y ago
> this will still just barely match the memory performance of Radeon 7600 Wow, I had no idea integrated GPUs had come this far. This is fantastic news.

rowanG077 3y ago

And even then memory channels is not really a marketable term for OEMs so not much is done to get that in. Only enthusiast (and thus really expensive) laptops go with a large number of memory channels.

wtallis 3y ago
There aren't any enthusiast laptops with more than a 128bit memory bus for the CPU, and memory channels and bus width are the wrong metrics to compare discrete GPUs where both width and clock speed vary widely across the entire product line.
- rowanG077 3y ago
  This isn't at all about discrete GPUs, where did you get that from? This is about APU/iGPUs. In general memory channel are expensive so you won't see a new product with 8 channels running 3000Mhz memory speed or something like that. Also Apple laptops do have large memory busses. The Apple M1 Max chip for example has a 512bit memory bus.
  - wtallis 3y ago
    I assumed when you said "Only enthusiast laptops go with a large number of memory channels" you intended to refer to something beyond just the MacBook Pro, because "enthusiast laptop" is usually used to describe a category that definitely includes a lot of laptops that aren't MacBook Pros, and only arguably includes some MacBook Pros. And if you did mean to refer specifically and only to MacBook Pros, there were plenty of more straightforward ways for you to do so.
    - rowanG077 3y ago
      It's quite simple really. Macbook Pro M1 Max is in the set of enthusiast laptops. You said there are none. I gave that as a counterexample. I wasn't specifically thinking about it in my original comment. In fact I wasn't specifically thinking about even a bus width that I consider "large". It was a general comment that memory channels are not cheap to have in a piece of silicon and that consumers generally don't care about it as a metric of performance.

jorvi 3y ago

I don’t know if this goes for VRAM, but I know that with system RAM, applications care very little about data rate and very much about timings. This includes games. I do know that overclocking VRAM (or at least GDDR6) barely increases performance, but that’s mostly because it’s usually already been pushed to the edge at stock. My old 3070Ti could easily overclock 10-15% higher, but the memory had to self-correct significantly more errors so the actual improvement was a wash. I’m also curious if gaming handhelds would benefit from switching their entire memory architecture over to VRAM, like both consoles have done in this generation.

ben-schaaf 3y ago
Timings are much less important for GPUs than bandwidth; the cores are slow and doing the same work on similar memory. A 3090 has ~270ns of memory latency - <70ns is normal for a CPU. See https://chipsandcheese.com/2021/05/13/gpu-memory-latencys-impact-and-updated-test/ https://chipsandcheese.com/2021/05/13/gpu-memory-latencys-im...
- jorvi 3y ago
  Maybe I’m misunderstanding the article, but there’s multiple places where they mention memory latency being the main bottleneck. At any rate, thanks for sharing! Interesting stuff.
  - lynguist 3y ago
    No, it’s really bandwidth. Big GPUs have on the order of 800 GB/s memory bandwidth and big CPUs only 80 GB/s! Except for Apple. They really need to up the bandwidth. GPU performance is proportional to both bandwidth and compute.

AnthonyMouse 3y ago

> The big break in this will be Strix Halo, coming from AMD either next year or late this year, as it will support 256-bit LPDDR5. Even using the fastest LPDDR5 available on the market, this will still just barely match the memory performance of Radeon 7600, the weakest current-gen discrete GPU AMD has on the market. You can do better than that simply by putting some HBM or GDDR6 on the APU itself. Then you don't need to change the socket or have to add memory channels, and you don't need that much of it because you still have the ordinary memory slots to provide some DDR5 where the OS can keep all its dreck bloat. 8-16GB of the stuff would be enough to rival any of the current midrange discrete GPUs.

DinaCoder99 3y ago

> this will still just barely match the memory performance of Radeon 7600 Wow, I had no idea integrated GPUs had come this far. This is fantastic news.