As someone who doesn't know very much about computer architecture, please excuse my ignorance, but why can't all of memory + CPU be located on the same chip? Does it cost more/ use more power/ etc? Why are buses used in the first place?
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yrkumar
@sbly: This actually has been explored: Computational RAM. The linked article suggests that the purpose of the various PIM (processor-in-memory) projects, the most notable of which was the Berkeley IRAM project, was to reduce memory latency and increase throughput. The main reason that it is difficult to put DRAM but not SRAM on the same chip as the processor is that the microprocessor technology for CPU chips optimizes for speed whereas DRAM chips optimize for density. SRAM can be built in the same way as the microprocessor technology, so it can more easily be put on the same chip.
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LilWaynesFather
Another more non-technical reason for why everything isn't located on the same chip is that many times buyers want modularity. If everything is on the same chip, if one part breaks, you have to replace the whole chip. If you want to upgrade just the memory/processor, you'd have to replace the whole chip. For supercomputers this would be a huge hassle. So they why not just fit tons of memory onto the same chip? Then the chip will probably get so large that you'll end up having the same issues that you did before with large distances between the processor and the memory.
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idl
System-on-a-chip architectures try to implement this too. It's kind of interesting to see how ARM architectures like the mobile devices take advantage of this, especially when physical space is precious.
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sluck
(Another person who knows little about computer architecture here) Would heat generation also be a problem? If you put more components that generate heat closer together, I'd imagine that the amount of heat would grow to the point that you would also have to design a way to remove the extra heat generated as a result of putting the components closer together.
As someone who doesn't know very much about computer architecture, please excuse my ignorance, but why can't all of memory + CPU be located on the same chip? Does it cost more/ use more power/ etc? Why are buses used in the first place?
This comment was marked helpful 0 times.
@sbly: This actually has been explored: Computational RAM. The linked article suggests that the purpose of the various PIM (processor-in-memory) projects, the most notable of which was the Berkeley IRAM project, was to reduce memory latency and increase throughput. The main reason that it is difficult to put DRAM but not SRAM on the same chip as the processor is that the microprocessor technology for CPU chips optimizes for speed whereas DRAM chips optimize for density. SRAM can be built in the same way as the microprocessor technology, so it can more easily be put on the same chip.
This comment was marked helpful 0 times.
Another more non-technical reason for why everything isn't located on the same chip is that many times buyers want modularity. If everything is on the same chip, if one part breaks, you have to replace the whole chip. If you want to upgrade just the memory/processor, you'd have to replace the whole chip. For supercomputers this would be a huge hassle. So they why not just fit tons of memory onto the same chip? Then the chip will probably get so large that you'll end up having the same issues that you did before with large distances between the processor and the memory.
This comment was marked helpful 0 times.
System-on-a-chip architectures try to implement this too. It's kind of interesting to see how ARM architectures like the mobile devices take advantage of this, especially when physical space is precious.
This comment was marked helpful 0 times.
(Another person who knows little about computer architecture here) Would heat generation also be a problem? If you put more components that generate heat closer together, I'd imagine that the amount of heat would grow to the point that you would also have to design a way to remove the extra heat generated as a result of putting the components closer together.
This comment was marked helpful 0 times.