A computer is powered by many microchips, all operating in sync. These microchips handle pretty much everything that the computer does. But not all microchips do the same thing. Each is dedicated to a particular task, though in some cases, that task is quite broad. Depending on the task, a computer might have one microchip performing a task or an extensive array of them.
There are two major classes of microchips: memory and logic. A memory chip is designed to store data. A logic chip is designed to operate on data. Some microchips will do some of each, though typically tending towards one over the other.
A DRAM chip is an example of a memory chip. It’s designed to store data so it can be accessed quickly and is used as system RAM. A 3D VNAND chip is also a memory chip. They are used in SSDs and provide high-speed long-term storage. A CPU is a prime example of a logic chip. It processes a vast amount of data performing logic operations on all of it to determine what should happen and instruct the rest of the computer. A GPU is another example of a logic chip. It processes graphics data according to its logic rules and then outputs data, typically to a screen.
No Hard and Fast Definitions
As previously mentioned, a logic chip doesn’t necessarily need only to perform logic; it can store data too. CPUs are once again a great example of this. A CPU has a small amount of onboard memory. This takes the form of cache memory, and the processor registers. Combined, they only store a few megabytes of data but can take up a surprisingly large percentage of the die area.
Its primary function is the key factor in determining if a chip is a logic chip or a memory chip. This doesn’t depend on the percentage of the die area used for what purpose or how much power a purpose takes. It’s just what the chip is used for. The memory in a CPU is to enable it to process logic as fast as possible.
The reverse would be true in a memory chip, for example, where the memory controller was integrated into the memory chip. While modern designs don’t do this, it would be possible. In that case, the controller’s processing power is there to optimize the memory chip. It would still be a memory chip.
Complexity
There are no particular rules for how much logic a logic chip needs to do to be a logic chip. A modern CPU, for example, has billions of transistors. This is part of what makes them excellent at the processing they do. It would be possible, however, to have a single logic gate on a microchip. Even though this theoretical chip is essentially just an XOR gate, for example, it is still a microchip that performs logic and, thus, a logic chip.
In the early days of computing, CPUs tended to come with extra coprocessors. One of these might be a floating-point processor. This was a logic chip designed to perform floating-point computations. Those floating-point coprocessors, however, could only do that. Still, they were microchips performing logical processes, and so were logic chips.
Conclusion
A logic chip is a microchip that is primarily designed to perform logic operations on data. It may or may not have some onboard storage space, but this does not make it a memory chip. Similarly, memory chips with small onboard processing power are not logic chips. Logic may be highly complex or incredibly simple, as the terminology does not imply complexity.
