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This talks about two major performance concerns in CPUs: control flow and memory access. The transition between the two was my favorite part of the article. It'

This talks about two major performance concerns in CPUs: control flow and memory access. The transition between the two was my favorite part of the article. It's both funny and accurate. "If the previous section gave the impression that, say, control flow is a particularly tough problem, but inventive methods can give powerful and practical tools to tackle it… good, that was the intent. In this section I want you to take that expectation and dash it against the rocks — memory is hard."

hinkley 7y ago
In the 90’s there was a group experimenting with putting small processors directly on the memory chips and doing data processing there.
- deepnotderp 7y ago
  Berkeley IRAM
- flohofwoe 7y ago
  This is also the idea behind the Pixel Planes rendering architecture from the 80's, they called it "logic-enhanced memory chips". It's not a "universal CPU" on the memory chips, but each chip can "process" and store 128 pixels, where the processing is implemented with a hardwired linear expression. Here's a video on Pixel Planes 4 from 1987: https://www.youtube.com/watch?v=7mzpZ861wEw https://www.youtube.com/watch?v=7mzpZ861wEw
  - leereeves 7y ago
    Sounds rather similar to GPU architecture.
    - thechao 7y ago
      Pixel Planes is the ancestor to GPUs with the identical relationship of the titans to the gods in Greek mythology.
- cfallin 7y ago
  There's still some research on this general idea -- e.g., a fellow grad student's work on in-memory bulk data operations: - https://archive.org/details/arxiv-1611.09988 https://archive.org/details/arxiv-1611.09988 (AND/OR/NOT in RAM) - https://www.pdl.cmu.edu/PDL-FTP/NVM/rowclone_micro13.pdf https://www.pdl.cmu.edu/PDL-FTP/NVM/rowclone_micro13.pdf (cloning data in RAM; full disclosure, I'm a co-author on this one) And IIRC at least one start-up (Emu Technology) that has built actual processing-in-memory (PIM) hardware.
- ip26 7y ago
  Of course when you start to look at how much die space is dedicated to SRAM on current CPU's, you begin to realize in a sense we have this now. Convergent evolution.
  - hinkley 7y ago
    Maybe we should just go NUMA and address the on die “cache” directly.
- verall 7y ago
  still a good way good way to get your phdce in computer architecture at least according to a couple profs i've talked to

hinkley 7y ago

In the 90’s there was a group experimenting with putting small processors directly on the memory chips and doing data processing there.

deepnotderp 7y ago
Berkeley IRAM
flohofwoe 7y ago
This is also the idea behind the Pixel Planes rendering architecture from the 80's, they called it "logic-enhanced memory chips". It's not a "universal CPU" on the memory chips, but each chip can "process" and store 128 pixels, where the processing is implemented with a hardwired linear expression. Here's a video on Pixel Planes 4 from 1987: https://www.youtube.com/watch?v=7mzpZ861wEw https://www.youtube.com/watch?v=7mzpZ861wEw
- leereeves 7y ago
  Sounds rather similar to GPU architecture.
  - thechao 7y ago
    Pixel Planes is the ancestor to GPUs with the identical relationship of the titans to the gods in Greek mythology.
cfallin 7y ago
There's still some research on this general idea -- e.g., a fellow grad student's work on in-memory bulk data operations: - https://archive.org/details/arxiv-1611.09988 https://archive.org/details/arxiv-1611.09988 (AND/OR/NOT in RAM) - https://www.pdl.cmu.edu/PDL-FTP/NVM/rowclone_micro13.pdf https://www.pdl.cmu.edu/PDL-FTP/NVM/rowclone_micro13.pdf (cloning data in RAM; full disclosure, I'm a co-author on this one) And IIRC at least one start-up (Emu Technology) that has built actual processing-in-memory (PIM) hardware.
ip26 7y ago
Of course when you start to look at how much die space is dedicated to SRAM on current CPU's, you begin to realize in a sense we have this now. Convergent evolution.
- hinkley 7y ago
  Maybe we should just go NUMA and address the on die “cache” directly.
verall 7y ago
still a good way good way to get your phdce in computer architecture at least according to a couple profs i've talked to