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"Processor-in-Memory", is an age-old idea which was even explored in a doctoral thesis from 1998: "Computational RAM: A Memory-SIMD Hybrid"*. At the time, the m
by roadbuster 1mo ago
"Processor-in-Memory", is an age-old idea which was even explored in a doctoral thesis from 1998: "Computational RAM: A Memory-SIMD Hybrid"*. At the time, the motivation was, "Between a DRAM chip and a microprocessor mounted on a circuit board, we can only get a few hundred megabytes per second of bandwidth. However, inside the memory chip itself, there's hundreds of gigabytes (terabits) of bandwidth available, so why not move some of the logic there?". And then the author pushed it to the extreme where there was a wide array of 1-bit processors at each column of DRAM. (Note: the reason why true PIM isn't viable is because of the radically different semiconductor process used for DRAM vs. high-speed digital logic, i.e.: your digital logic circuits will perform poorly on a "DRAM process").
The designers of HBM5 had the same observations and thought, "why don't we put a logic chip at the bottom of the stack of HBM DRAM chips and get extremely high memory bandwidth?" But, in looking at this, you'll also quickly realize this is almost exactly what Intel and Micron pitched 15 years ago as Hybrid Memory Cube** (which lost on the market compared to the simpler, less costly, and more flexible alternative, HBM)
* https://www.eecg.toronto.edu/~stumm/Theses/Elliott-PhD98.pdf https://www.eecg.toronto.edu/~stumm/Theses/Elliott-PhD98.pdf
** https://en.wikipedia.org/wiki/Hybrid_Memory_Cube https://en.wikipedia.org/wiki/Hybrid_Memory_Cube
- hn_acc1 1mo agoDuncan Elliott taught my graduate (IIRC) computer architecture course while writing that thesis - we all talked about C-RAM for a while.. And I think it was a rehash of an even older paper / discussion about that idea.
- jhgorrell 1mo agoI have been reading about this for the last 25 years. So, yea, in another 25 years "this will be a thing".
- timcobb 1mo agoAge-old... 1998... :grimace:
- Bratmon 1mo agoRemember: 1998 is as old now as 1970 was in 1998.
- schaefer 1mo agoI don’t think he was asking you to twist the knife.
- timcobb 1mo agoEh it's okay. It's just that, man, computers were already so well along by 1998, when I hear "age-old" I think like the 60s, 70s, _maybe_ 80s--but 90s?! oh well! I did a few double takes assuming my mind had flipped the 9 and 8 in 98, but no :D.
- margalabargala 1mo agoAt this point, "age-old" means "64-bit processors were not the default".
- Bratmon 1mo agoRemember: AMD64 is as old now as the 286 was when AMD64 came out!
- deleted 1mo ago[deleted]
- snailmailman 1mo agoI think it goes back further than 1998. Several old systems had special memory locations where the numbers written would then read back changed. The Apollo Guidance computer for instance didn’t have a shift-right or shift-left cpu instruction. They would write data to a specific area of memory that would modify the data to shift bits around. Although I’m sure it’s quite different. The cpu and memory hardware is so completely different. And basic bit manipulation is hardly computation.
- inigyou 1mo agoThat's transport triggered architecture and it's the same hardware with a different ISA. This is different hardware.
- genxy 1mo agohttps://dblp.org/pid/m/OnurMutlu.html https://dblp.org/pid/m/OnurMutlu.html (search for "processing") also has a ton of great lectures on youtube, https://www.youtube.com/results?search_query=onur+mutlu+processing+in+memory https://www.youtube.com/results?search_query=onur+mutlu+proc... 99 page primer on PIM https://arxiv.org/abs/2012.03112 https://arxiv.org/abs/2012.03112 https://en.wikipedia.org/wiki/Berkeley_IRAM_project https://en.wikipedia.org/wiki/Berkeley_IRAM_project