PoetPhilosopher
Veteran Member
Today I'm going to explain unified memory, a type and model of RAM which some computer-type devices these days are using, and my explanation is going to get technical, though I'm hoping it's actually a little less technical and more detailed still, than some of the technical articles of the subject that are on the web.
A limited amount of devices (Playstation 5, Mac Mini, etc) are using a technology known as unified computer memory, not to be confused with the worser "shared memory" which is when a portion of normal system RAM on a computer becomes allocated and used as if it is Video RAM (the memory which the GPU of a computer generally accesses).
Unified memory is when any portion of RAM can be used for different things across the CPU and GPU. And here is what I consider to be the main benefit of this "unified memory" found in PlayStation 5 and XBox Series X, Mac Mini and Mac Studio, the NVIDIA Orin, etc.
On a normal computer system without unified memory, one of two things often happens while playing a video game or using a graphical application (like 3D modeling, etc, or even most normal applications). Some of the graphics or textures (if not all of them), are stored in system RAM. But then one of two other things happen as the GPU of the system processes the graphics:
1. A separate copy of the graphics or textures in system RAM is then saved in the Video RAM so that the GPU can access it, creating two copies (one in system RAM, one in Video RAM). This consumes more memory overall.
Or:
2. The contents of system RAM are transferred to Video RAM or back to system RAM as needed. This may not necessarily consume more memory, but it consumes more memory bandwidth - which can slightly hinder performance or framerate as the computer does these operations (because moving items back and forth between system RAM and Video RAM can be quite slow and intensive, even on modern computers).
However, with unified memory, it tries to actually make it so that both the CPU and GPU are able to access the same copy of graphics or texture data, even at the same time - this can save memory and memory bandwidth, freeing memory and speeding things up.
This is in the most ideal scenario, though. There are some computer softwares where the driver software of the GPU may still decide that some graphics or textures still need two copies, even in unified memory (in the case of unified memory, two copies may be created - both in unified memory). But overall, there is generally still a memory and performance savings from unified memory. One might ask how if it may do some of the same things as the ordinary, non-unified memory most computers use, how it's still better than non-unified memory. My answer is that the key word here is "some" - for example, some graphics or textures may still get copied twice in unified memory, but generally, the effects are still significantly better than with standard memory (which either duplicates more data, or has to swap it back and forth between two pools of RAM).
Resources:
What is Unified Memory and how does it work on Apple Silicon?
Central processing unit - Wikipedia
Graphics processing unit - Wikipedia
Memory bandwidth - Wikipedia
Tl;Dr or simpler explanation - Unified memory reduces the copying and duplication that comes with having separate pools of RAM for system and GPU. Which can reduce the amount of memory used on a task, and/or increase performance - over not having unified memory.
A limited amount of devices (Playstation 5, Mac Mini, etc) are using a technology known as unified computer memory, not to be confused with the worser "shared memory" which is when a portion of normal system RAM on a computer becomes allocated and used as if it is Video RAM (the memory which the GPU of a computer generally accesses).
Unified memory is when any portion of RAM can be used for different things across the CPU and GPU. And here is what I consider to be the main benefit of this "unified memory" found in PlayStation 5 and XBox Series X, Mac Mini and Mac Studio, the NVIDIA Orin, etc.
On a normal computer system without unified memory, one of two things often happens while playing a video game or using a graphical application (like 3D modeling, etc, or even most normal applications). Some of the graphics or textures (if not all of them), are stored in system RAM. But then one of two other things happen as the GPU of the system processes the graphics:
1. A separate copy of the graphics or textures in system RAM is then saved in the Video RAM so that the GPU can access it, creating two copies (one in system RAM, one in Video RAM). This consumes more memory overall.
Or:
2. The contents of system RAM are transferred to Video RAM or back to system RAM as needed. This may not necessarily consume more memory, but it consumes more memory bandwidth - which can slightly hinder performance or framerate as the computer does these operations (because moving items back and forth between system RAM and Video RAM can be quite slow and intensive, even on modern computers).
However, with unified memory, it tries to actually make it so that both the CPU and GPU are able to access the same copy of graphics or texture data, even at the same time - this can save memory and memory bandwidth, freeing memory and speeding things up.
This is in the most ideal scenario, though. There are some computer softwares where the driver software of the GPU may still decide that some graphics or textures still need two copies, even in unified memory (in the case of unified memory, two copies may be created - both in unified memory). But overall, there is generally still a memory and performance savings from unified memory. One might ask how if it may do some of the same things as the ordinary, non-unified memory most computers use, how it's still better than non-unified memory. My answer is that the key word here is "some" - for example, some graphics or textures may still get copied twice in unified memory, but generally, the effects are still significantly better than with standard memory (which either duplicates more data, or has to swap it back and forth between two pools of RAM).
Resources:
What is Unified Memory and how does it work on Apple Silicon?
Central processing unit - Wikipedia
Graphics processing unit - Wikipedia
Memory bandwidth - Wikipedia
Tl;Dr or simpler explanation - Unified memory reduces the copying and duplication that comes with having separate pools of RAM for system and GPU. Which can reduce the amount of memory used on a task, and/or increase performance - over not having unified memory.
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