Why cannot a CPU be used as a GPU?

[archerbob]

How could one custom build a GPU?

 

 

[Enzo1001]

Just now, archerbob said:

How could one custom build a GPU?

 

 

actually i had the same thought, why the vram and gpu chips, cooler arent swapable

[Alex Atkin UK]

6 minutes ago, Enzo1001 said:

actually i had the same thought, why the vram and gpu chips, cooler arent swapable

 

[mariushm]

A gpu chip has a lot of very simple cores , hundreds or thousands of them, with just a few specialized functions, and all these "cores" can work in parallel on parts of each frame drawn on the screen to make lots of frames per second.

A cpu has much more complex cores which can do a lot of complex operations.

 

The vram on video card is needed to store as close as possible to the gpu cores the information about what's in the frame and the textures that get applied over all the items in the frame ... ex a tree, a door, wall of a building, etc ... everything is made out o thousands of polygons and triangles, and textures are applied over those triangles to make the picture you see.

 

You can't custom build a video card because it's just harder... you're dealing with memory chips that must be much closer to the gpu chip, can't have them on sticks because the extra distance and wire resistance of the slots would cause issues. those memory chips run at higher frequencies.

It's also pointless to have a gpu chip on a socket, because for example you could have a gtx 1050 ti chip that consumes under 60w or you could have a rtx3070 chip which consumes 250 watts ... it would be silly to make the  buyer spend 100$ or so on the base video card circuit board with a VRM (dc-dc converter) capable of supplying 300w to a gpu chip, if that gpu chip only consumes 60w.

 

 

[Moonzy]

6 minutes ago, mariushm said:

it would be silly to make the  buyer spend 100$ or so on the base video card circuit board with a VRM (dc-dc converter) capable of supplying 300w to a gpu chip, if that gpu chip only consumes 60w

Yet it's acceptable to design motherboard that caters to a wide range of CPU power consumption, don't think this argument makes sense lol

[BlueChinchillaEatingDorito]

18 minutes ago, Enzo1001 said:

actually i had the same thought, why the vram and gpu chips, cooler arent swapable

A big issue would be power delivery. It's technically possible to design a board where with the necessary power delivery to different configurations of GPU dies and VRAM... but it's just not practical. Everything would have to at least support the highest tier GPU in order to make it worth while. There are more complex explanations but I'm not going down that endless rabbit hole. 

 

I would recommend giving this thread a read as it was discussed prior.

 

[shadow_ray]

>Why cannot a CPU be used as a GPU?

 

actually the CPU can be used as a GPU... it's just going to be slllooooowww for the reasons @mariushm described above

i think mesa OpenGL drivers have this functionality: "A software implementation of OpenGL is useful for experimentation, such as testing new rendering techniques."

 

And i think Linus ran crisis on a threadripper in one video... or something similar

[Jeskspie]

32 minutes ago, archerbob said:

How could one custom build a GPU?

 

 

async.

[shadow_ray]

yep

 

[heimdali]

You probably need some kind of factory to manufacture the chips your GPU is made of ...

 

[Lurick]

56 minutes ago, archerbob said:

How could one custom build a GPU?

 

 

You need a small loan of about $20 billion to start

[Alex Atkin UK]

7 hours ago, shadow_ray said:

>Why cannot a CPU be used as a GPU?

 

actually the CPU can be used as a GPU... it's just going to be slllooooowww for the reasons @mariushm described above

i think mesa OpenGL drivers have this functionality: "A software implementation of OpenGL is useful for experimentation, such as testing new rendering techniques."

 

And i think Linus ran crisis on a threadripper in one video... or something similar

In fact it often IS used for 2D at least, when using something like VNC for a virtual desktop (not mirroring a real one so no GPU rendering).

 

Also when using Linux due to lack of standards video playback is often done on the CPU whereas on Windows/Mac the GPU decode blocks will do it saving a ton of CPU resources.

[thekingofmonks]

On 10/3/2021 at 2:18 AM, shadow_ray said:

>Why cannot a CPU be used as a GPU?

 

actually the CPU can be used as a GPU... it's just going to be slllooooowww for the reasons @mariushm described above

i think mesa OpenGL drivers have this functionality: "A software implementation of OpenGL is useful for experimentation, such as testing new rendering techniques."

 

And i think Linus ran crisis on a threadripper in one video... or something similar

You can use Cinebench as an example

[Mark Kaine]

Actually it can,  my Fujitsu with a Pentium CPU can play any 3D games from around 1995 i throw at it no problem...

I always knew I could buy a "voodoo card" or something, I just never understood why lol so I didn't...

 

Also tbh, I'm pretty sure a GPU is just a CPU, just different architecture with a lot of "cores" or whatever  

 

On 10/2/2021 at 7:59 PM, mariushm said:

you're dealing with memory chips that must be much closer to the gpu chip, can't have them on sticks because the extra distance and wire resistance of the slots would cause issues

Eh, isn't that exactly what consoles do though? I think there are pros and cons for both solutions and its not "it can only be done like this" at all.

 

One argument pro unified memory could be PCs finally wouldn't be limited by low vram most GPUs come with...

 

And no, there's also no reason why a PC couldn't have the fastest RAM available instead of the cheapest ... afaik.

 

[Vishera]

5 minutes ago, Mark Kaine said:

Also tbh, I'm pretty sure a GPU is just a CPU, just different architecture with a lot of "cores" or whatever  

They are both processing units,just designed for different purposes.

GPU - Graphics Processing Unit

CPU - Central Processing Unit

[Stahlmann]

You can use your CPU to "software render" your frames. Thing is, the CPU core is MUCH slower at it than a dedicated GPU core.

 

That's about as simple as i can keep it.

[Parvesh Khatri]

CPUs are dumb in solving graphics, just like me, in solving math problems. GPUs are designed to be quick in solving graphics related problems, which are easy to solve but there are hell a lot of them, so GPUs have hell a lot of smaller cores. Buttt, GPUs are dumb in solving large problems which CPUs are good at, because they have fewer but more capable cores.

[RoseLuck462]

The architectures are too different, otherwise you’d have Intel and AMD  CPUs being touted for their graphics capabilities.

[Guest willies leg]

Sure it can, the same way a GPU can be used as a CPU.

Of course it's not too efficient, a CPU as a GPU will be really slow ("software renderer")  same as a GPU running as a CPU, really poorly. https://www.nvidia.com/en-us/geforce/forums/gaming-pcs/8/265725/dawn-operating-system-boots-and-runs-fully-on-gpu/

 

Just because you can doesn't mean you should.

 

 

[flindeberg]

On 10/2/2021 at 7:49 PM, archerbob said:

How could one custom build a GPU?

At a very broad and general level a CPU can do everything a GPU can, and more, but they are optimised for different use-cases. GPUs are essentially CPUs optimized for large matrix multiplications of floats. And as it turns out you can do a lot with matrix multiplications of floats (machine learning, AI, or whatever you want to call it). CUDA cores (Nvidia) and Stream processors (AMD) are essentially small accumulators optimised for floating point arithmetics, which together with a lot of other accumulators are optimised for matrices. 

 

If you are interested at a technical level look at how the late nineties SIMD instruction-sets for x86 CPUs MMX, SSE and AVX started doing essentially what GPUs do today. 

 

An interesting project on the topic is the Intel Larrabee project, which tried to put fully programmable microprocessors in arrays to form a GPU, rather than the only partially programmable more accumulator like entities of then current Nvidia and Radeon products. 

[aramini]

4 hours ago, Vishera said:

They are both processing units,just designed for different purposes.

GPU - Graphics Processing Unit

CPU - Central Processing Unit

A CPU would be an example of a more generalized processor whereas a GPU is highly specialized/optimized for the task of rendering graphics, especially when you get into the higher end GPU/cards.

 

43 minutes ago, flindeberg said:

An interesting project on the topic is the Intel Larrabee project, which tried to put fully programmable microprocessors in arrays to form a GPU, rather than the only partially programmable more accumulator like entities of then current Nvidia and Radeon products.

Which is kinda the opposite of what crypto miners do, use the less expensive (depending on the card) GPUs and many of them to work on completing the hash blocks instead of having the CPU do the work. Because as you stated...

 

44 minutes ago, flindeberg said:

GPUs are essentially CPUs optimized for large matrix multiplications of floats.

 

[Sauron]

On 10/2/2021 at 7:49 PM, archerbob said:

How could one custom build a GPU?

 

[archerbob]

What about the making of a card using the BGA chip from an old laptop for a 2060, I've see old broken laptops that have decent graphics chips in them.

 

Is it in the realm of possibility for the home user to create the PCB needed to hot air the GPU BGA chip to a PCIe card?

[Mark Kaine]

2 hours ago, flindeberg said:

An interesting project on the topic is the Intel Larrabee project,

Another one was IBM Cell processor,  with the advantage that actually worked and sold millions...

 

Would have been super interesting if Sony went ahead with their initial plan to use two of them and therefore one for graphics rendering,  i believe they didn't due to heat mostly, the original PS3s ran hot as hell, but the concept was way ahead of its time,  true "multi purpose" processors... think Alderlake is a similar concept,  even just general "multi threaded" CPUs were kinda the evolution of that IBM / Sony chip.

 

In hindsight it was probably not super ideal for gaming consoles (way too many issues) doesn't make it any less forward thinking though. 

 

5 hours ago, Sauron said:

 

Haha, this is so cool. That's actually kinda what these "voodoo" cards were? They even look similar albeit more complex obviously.

 

Sidenote: dude sounds like vwwestlife,  wonder if there's a connection...even the video style is very similar...

[Freakwise]

6 minutes ago, archerbob said:

Is it in the realm of possibility

yes

6 minutes ago, archerbob said:

for the home user to create the PCB needed to hot air the GPU BGA chip to a PCIe card?

no

 

home user (depending on what you meant by that) isnt going to bother doing all of the stuff that require to make that mobile gpu works as normal pcie card gpu, i mean it sounds fairly easy at first right? just take it out from laptop and resolder it to the card

until you realized you need to design the pcb (obviously), and hope someone on the internet upload a schematic of that spesific moblle gpu not to mention the trial and error that goes along the way