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- Jun 10, 2014
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Processor | AMD Ryzen 9 5900X ||| Intel Core i7-3930K |
---|---|
Motherboard | ASUS ProArt B550-CREATOR ||| Asus P9X79 WS |
Cooling | Noctua NH-U14S ||| Be Quiet Pure Rock |
Memory | Crucial 2 x 16 GB 3200 MHz ||| Corsair 8 x 8 GB 1333 MHz |
Video Card(s) | MSI GTX 1060 3GB ||| MSI GTX 680 4GB |
Storage | Samsung 970 PRO 512 GB + 1 TB ||| Intel 545s 512 GB + 256 GB |
Display(s) | Asus ROG Swift PG278QR 27" ||| Eizo EV2416W 24" |
Case | Fractal Design Define 7 XL x 2 |
Audio Device(s) | Cambridge Audio DacMagic Plus |
Power Supply | Seasonic Focus PX-850 x 2 |
Mouse | Razer Abyssus |
Keyboard | CM Storm QuickFire XT |
Software | Ubuntu |
No memory controller works the way you describes.Now imagine a lopsided memory chip with just 3 locations. You will still need to build the infrastructure for 4 addresses into the chip, since the top bit is still being set, ie value 2 (10 binary) with the top address of 3 (11 binary) pointing nowhere and likely having to be masked off to avoid a crash. Hence the chip will still take the same number of transistors as if it had 4 locations, but not actually have that extra location in it and therefore the chip will not be an optimal design. Of course, what you get back is that the extra circuitry for the 4th location is missing, saving space, hence making for a compromise.
For starters, the memory controllers on GPUs have all power of 2 address space as I've said a number of times already, how hard is this to understand?
But for the hypothetical scenario where 3 out of 4 memory slots i occupied, the memory controller will never check if a memory address is inside the range on read/write, that would be too costly anyway. The whole "problem" is solved on allocation of memory (which is costly anyway, and done very rarely compared to read/write), and the only thing to check then is whether the memory address is above the maximum size, so the problem you describes doesn't exist.
Just to illustrate how wrong you are, I checked two of the machines I'm running here;
i7-3930K, 46-bit controller, 65536 GB (64 TB) theoretical physical address space, but the CPU is "limited" to 64 GB.
i5-4690K, 39-bit controller, 512 GB theoretical physical address space, but the CPU is "limited" to 32 GB.
(This is fetched directly from the CPU's cpuid instruction, so it's what the OS sees and is guaranteed to be correct)
Number of bits of what? Data bus? Memory bus? Register width?You have a similar situation regardless of what you're addressing, whether it's CUDA units and the number of bits they each handle in a GPU, or the number of CUDA units in the GPU, or whatever aspect of a digital circuit.
If you look at GPU architectures you'll see that most of then don't have a core count which adds up to a power of 2, like 256, 512, 1024, 2048, 4096, etc. Just scroll through here and here, that power of 2 is more the exception than the rule.
The term "a perfect power of 2 chip" doesn't make any sense.The problem in the real world of course, is that building a perfect power of 2 chip causes the number of transistors and physical size of that chip to double each time it's expanded, ie to grow exponentially which is unsustainable.
The GTX 970 "issue" was that two memory chips shared one 32-bit controller, while the others didn't, creating an address space where some of it was slower without the allocator taking this into account. Power of 2 had absolutely nothing to do with it.The 970 memory issue came about, because NVIDIA nibbled a bit off the GPU, giving rise to a compartmentalized memory addressing design, where they chose to use slow RAM for that last 500MB, but didn't declare it, leading to this scandal.
When I saw that the 1080 Ti with its weird 11GB RAM and crippled GPU, it brought back to me that NVIDIA could potentially have the same design issue…
If GTX 1080 Ti were to do the same thing it would have to do 12 memory chips on 11 controllers, which we know it doesn't, so we know it can't happen. If you still think it's a problem, then you're having a problem understanding how processors and memory work.
Your avatar is cool though.Oh and you asked for it - check my sig!