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Ask HN: In Apple parlance, why is the motherboard called the logic board?

3 points by kunai 13y ago

Title says all.

daenney 13y ago
Because Apple is our mother. She is so much she can hardly be encompassed in something simple as a board with a bunch of chips. But all the logic, the brainpower of her children, is located on such a board. Therefor it's only logical this be called a logic board.
blakdawg 13y ago
Older Macs with built-in monitors had two main circuit boards - a video board and a "logic" board with the CPU, RAM, etc.
marssaxman 13y ago
On the original Macintosh, there were two circuit boards: the "analog board" contained the power supply and CRT driver, while the "logic board" held the microprocessor and all the digital logic. At the time, "motherboard" was a more general term, describing any arrangement where "daughterboards" plugged into sockets on a "motherboard".
- Someone 13y ago
  I think you mean _less_ general. A motherboard must allow daughter boards to be plugged in. On the other hand, http://www.imsai.net/download/IEEE_696_1983.pdf http://www.imsai.net/download/IEEE_696_1983.pdf uses it for he board that generates the clock signal: "The memory write strobe, MWRT, shall be generated somewhere in the system. It has traditionally been generated by front-panel type devices, but is optionally generated by permanent masters or mother boards in systems without front panels" In my memory, however, the term 'motherboard' originated with the PC and is restricted to the PC. For example, I can't find the term in Wikipedia's article on the S-100 bus (http://en.wikipedia.org/wiki/S-100_bus http://en.wikipedia.org/wiki/S-100_bus), the Apple II reference manual (http://ia600602.us.archive.org/19/items/applerefjan78/appleIIrefjan78.pdf http://ia600602.us.archive.org/19/items/applerefjan78/appleI...), or the Macintoh II service manual (http://tim.id.au/laptops/apple/legacy/macintosh_ii.iix.iifx.pdf http://tim.id.au/laptops/apple/legacy/macintosh_ii.iix.iifx....) They use terms 'processor board', 'board', and 'logic board'.
  - marssaxman 13y ago
    I mean that a PC motherboard is a specific type of "mother board", which is a board into which one plugs "daughter boards", aka expansion cards. I have vague recollections of this terminology being used in the late '80s to describe machines with upgradeable processors, and have thus imagined that this is where the modern sense of "motherboard" comes from. But it was 25 years ago or more, so my memory may not be accurate.
  - mtdewcmu 13y ago
    > the term 'motherboard' originated with the PC and is restricted to the PC I guess it doesn't make a difference that Macs are now PCs?

3 points by kunai 13y ago

Title says all.

Because Apple is our mother. She is so much she can hardly be encompassed in something simple as a board with a bunch of chips. But all the logic, the brainpower of her children, is located on such a board. Therefor it's only logical this be called a logic board.

blakdawg 13y ago

Older Macs with built-in monitors had two main circuit boards - a video board and a "logic" board with the CPU, RAM, etc.

marssaxman 13y ago

On the original Macintosh, there were two circuit boards: the "analog board" contained the power supply and CRT driver, while the "logic board" held the microprocessor and all the digital logic. At the time, "motherboard" was a more general term, describing any arrangement where "daughterboards" plugged into sockets on a "motherboard".

Someone 13y ago
I think you mean _less_ general. A motherboard must allow daughter boards to be plugged in. On the other hand, http://www.imsai.net/download/IEEE_696_1983.pdf http://www.imsai.net/download/IEEE_696_1983.pdf uses it for he board that generates the clock signal: "The memory write strobe, MWRT, shall be generated somewhere in the system. It has traditionally been generated by front-panel type devices, but is optionally generated by permanent masters or mother boards in systems without front panels" In my memory, however, the term 'motherboard' originated with the PC and is restricted to the PC. For example, I can't find the term in Wikipedia's article on the S-100 bus (http://en.wikipedia.org/wiki/S-100_bus http://en.wikipedia.org/wiki/S-100_bus), the Apple II reference manual (http://ia600602.us.archive.org/19/items/applerefjan78/appleIIrefjan78.pdf http://ia600602.us.archive.org/19/items/applerefjan78/appleI...), or the Macintoh II service manual (http://tim.id.au/laptops/apple/legacy/macintosh_ii.iix.iifx.pdf http://tim.id.au/laptops/apple/legacy/macintosh_ii.iix.iifx....) They use terms 'processor board', 'board', and 'logic board'.
- marssaxman 13y ago
  I mean that a PC motherboard is a specific type of "mother board", which is a board into which one plugs "daughter boards", aka expansion cards. I have vague recollections of this terminology being used in the late '80s to describe machines with upgradeable processors, and have thus imagined that this is where the modern sense of "motherboard" comes from. But it was 25 years ago or more, so my memory may not be accurate.
- mtdewcmu 13y ago
  > the term 'motherboard' originated with the PC and is restricted to the PC I guess it doesn't make a difference that Macs are now PCs?