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[scriver]

Chairs are right to have toes. They're dirty and smell and always put themselves on top of them.

[methylatedspirit]

I wonder why GPU core counts are usually either a power of two or are the sum of a few powers of two. For example:
The R7 265 has 1024 cores. 1024 = 2¹⁰.
The GTX 1080 has 2560 cores. 2520 = 2¹¹ + 2⁹.
The GTX 1070 Ti has 2432 cores. 2432 = 2¹¹ + 2⁸ + 2⁷.
The Radeon VII has 3480 cores. 3480 = 2¹¹ + 2¹⁰ + 2⁹ + 2⁸.

Is there a reason for this, or have I been playing Spot the Pattern for too long?

Fakedit: And I suppose the same thing happens with CPU core counts, but when the "weirdest" number you'll get (as far as mainstream consumer and HEDT processors go) there is 6 and its multiples (12, 24), it somehow feels less significant.

[wierd]

Many forms of computation, especially related to graphics processing, are greatly eased by utilizing the natural squaring capabilities one gets when using powers of two.

Additionally, binary counting naturally lends itself to power-of-two exponentiation, and addressing cores in an efficient manner ends up making this the easiest path to take.

While one could indeed have odd numbers of cores, and have non-power-of-two numbers of cores, it ends up being annoying to programmers, and overall inefficient.

[Eschar]

Addressing uses binary numbers, so if you want more cores and you have to make your addresses longer, adding one digit to the end will double the amount of cores you can address. Repeatedly doubling like this gets you powers of two.

[Reelya]

I wonder why GPU core counts are usually either a power of two or are the sum of a few powers of two. For example:
The R7 265 has 1024 cores. 1024 = 2¹⁰.
The GTX 1080 has 2560 cores. 2520 = 2¹¹ + 2⁹.
The GTX 1070 Ti has 2432 cores. 2432 = 2¹¹ + 2⁸ + 2⁷.
The Radeon VII has 3480 cores. 3480 = 2¹¹ + 2¹⁰ + 2⁹ + 2⁸.

Is there a reason for this, or have I been playing Spot the Pattern for too long?

Fakedit: And I suppose the same thing happens with CPU core counts, but when the "weirdest" number you'll get (as far as mainstream consumer and HEDT processors go) there is 6 and its multiples (12, 24), it somehow feels less significant.

Well you need to consider what form factor the cores come in. With that many cores, they're not shipping individual cores, they're going to have some architecture, with modules, and each module is going to have an addressing scheme for cores in its package. For example, they could be designed around an architecture where they have sections of 128 cores each, and that section locally uses 7-bit addressing. Then, they chunk X amount of these segments on a chip, put Y amount of chips on the card, and that's your core count. You use powers of 2 per chip since that allows you to have an exact integer amount of address bits, which leads to more efficient use of the silicon space and simpler wiring.

As for some of the odd sizes, such as the GTX 1070 Ti, which is 19 times 128, I have a strong suspicion that this is just a GTX 1080 where they put one of the reject chips. Say they make chips with 512 cores, then you put 5 chips on a board and you have 2560 cores. But, each chip has some chance that there will be a flaw in the silicon. So you test every chip that's fabbed, and some won't work at all, some will work but only at a lower clock speed, some will have *some* cores that work but not others. So they might decide that chips in which 3/4 of the cores work are cost-effective to salvage, but no less. You can then collect all these reject chips and put 1-per-card to make a 2432 core card instead of a 2560 core card. This is most likely they story behind the GTX 1070 Ti vs the GTX 1080, since the 1070 Ti came out several months later.

[bloop_bleep]

Hold on Reelya, do you mean that they reuse the chips that work or somewhat work on the 1070 Ti, or that they reuse the chips that don't work on the 1070 Ti?

[wierd]

Re-binning has been a thing for a very very long time.

Basically, you have some chips on each run that come out a little off-spec but can still do useful work. Maybe it cant run at the advertised clockrate. Maybe a few of its cores are wonky. Whatev.  So, you create a discount line of products that can use those chips so that they can still be sold. You add some wire jumpers on the board the chip is installed on, or you send the chip a microcode patch to change the number of cores, and nobody is the wiser.

Intel has been doing that since at least the 486. (The SX chip is a DX chip with a defect math processor, which is disabled, for instance. Or a pentium 120. Its a rebinned 133 that does not run stable at 133.)

[Iduno]

It's not just computers. We also have Keystone, Busch, etc.

[Reelya]

Hold on Reelya, do you mean that they reuse the chips that work or somewhat work on the 1070 Ti, or that they reuse the chips that don't work on the 1070 Ti?

Let me explain the history here.

Silicon wafers have defects on them. Any circuitry that's printed where the defect is will be shit basically. So, you want the things you're printing on the silicon to be individually small. If your chip was the size of the entire wafer then if there was even one flaw in the silicon, the entire wafer would need to be thrown away. So, one of the benefits of shrinking dies is that you waste less % of the silicon if there are flaws. It's as if you're printing something on paper, and if there's a hole in the paper you need to throw that sheet out, but you shrink your type so that each document takes up 1/4 of the page, then you only need to throw out the 1/4 of the page with the hole in it.

This means less overall wastage, since you're only throwing out the bit of the silicon where the defect is, not the whole sheet. However, small things lack the economy of scale. Imagine if they printed every single GPU core as it's own chip, then had 2560 individual chips in the video card? So, they want to package many things on an individual chip because that's good for economies of scale (less chips per card) but it's bad because you'll end up with more dead chips if you do that due to pre-existing defects in the silicon per area.

So, instead what they do is package many components on the same die, but they do it in a way that's modular, so you can test how much of each chip is usable, then you grade them based on that. EDIT: looks like all the GPUs are actually in one package, but they're modular down to 128 so they can turn that many cores off and sell it as a cheaper card. Note that the 1070 Ti came out the year after the 1080, and has 128 less cores (2560 down to 2432), while the 1070 care out a year after the 980, and also has 128 less cores (2048 down to 1920). So this suggests the 1070 line "gaming perfected" is in fact a line of cards designed to soak up all the reject chips from their flagship line.

[methylatedspirit]

Intel has been doing that since at least the 486. (The SX chip is a DX chip with a defect math processor, which is disabled, for instance. Or a pentium 120. Its a rebinned 133 that does not run stable at 133.)

AMD took it a step further in 2007 with their Phenom series of chips. They made quad-core chips, but some of them had a defective core. Instead of dumping them or selling them off as dual-cores, they sold them as Phenom X3 chips, quite literally tri-core CPUs. If you had a nice motherboard (and assuming you got lucky with the chip you had), you could unlock that missing core and get the performance of an X4 (quad-core) chip for the price of an X3.

[Frumple]

So human fingers and such have oils on them or somethin'. It's why we basically destroy monuments and whatnot of you let people touch them.

Has anyone tried to, like. Collect that? If so, what were they trying to do with it?

[bloop_bleep]

Hold on Reelya, do you mean that they reuse the chips that work or somewhat work on the 1070 Ti, or that they reuse the chips that don't work on the 1070 Ti?

Let me explain the history here.

Silicon wafers have defects on them. Any circuitry that's printed where the defect is will be shit basically. So, you want the things you're printing on the silicon to be individually small. If your chip was the size of the entire wafer then if there was even one flaw in the silicon, the entire wafer would need to be thrown away. So, one of the benefits of shrinking dies is that you waste less % of the silicon if there are flaws. It's as if you're printing something on paper, and if there's a hole in the paper you need to throw that sheet out, but you shrink your type so that each document takes up 1/4 of the page, then you only need to throw out the 1/4 of the page with the hole in it.

This means less overall wastage, since you're only throwing out the bit of the silicon where the defect is, not the whole sheet. However, small things lack the economy of scale. Imagine if they printed every single GPU core as it's own chip, then had 2560 individual chips in the video card? So, they want to package many things on an individual chip because that's good for economies of scale (less chips per card) but it's bad because you'll end up with more dead chips if you do that due to pre-existing defects in the silicon per area.

So, instead what they do is package many components on the same die, but they do it in a way that's modular, so you can test how much of each chip is usable, then you grade them based on that. EDIT: looks like all the GPUs are actually in one package, but they're modular down to 128 so they can turn that many cores off and sell it as a cheaper card. Note that the 1070 Ti came out the year after the 1080, and has 128 less cores (2560 down to 2432), while the 1070 care out a year after the 980, and also has 128 less cores (2048 down to 1920). So this suggests the 1070 line "gaming perfected" is in fact a line of cards designed to soak up all the reject chips from their flagship line.

I understand how silicon chips are made, I was just wondering whether they have completely defective cores on the 1070 Ti but still count them or not. Thanks for clarifying.

So human fingers and such have oils on them or somethin'. It's why we basically destroy monuments and whatnot of you let people touch them.

Has anyone tried to, like. Collect that? If so, what were they trying to do with it?

Collect that? For what? Sebum has fatty acids and their compounds rather than hydrocarbons, if that's what you're thinking. I doubt that would be cost-effective to try to convert the fatty acids back into hydrocarbons either, since fatty acids from other sources are much more available and I haven't heard of any massive hydrocarbon production lines from those.

[Frumple]

I mean, I don't know why you'd do it, other than for whatever reason you collect similar materials. That's why I was asking

Probably most curious if anyone had tried to cook with it somehow, but any use for it besides destroying stalagmites would be neat to hear about.

[methylatedspirit]

I got my brother's old laptop, a Lenovo Yoga 2 Pro. The keyboard and touchpad are on their last legs, and it's in poor physical shape. What can I do with it that isn't "disassemble it and cannibalize it for parts", "use it as a HTPC" (already have one) or "destroy it"?

[bloop_bleep]

Send it to a charity? Better than destroying it, at least.