February 5th, 2016

Hard Stare

Why do Macs have "logic boards" while PCs have "motherboards"?

Since it looks like my FB comment is about to get censored, I thought I'd repost it...


Gods, you are such a bunch of newbies! Only one comment out of 20 knows the actual answer.

History lesson. Sit down and shaddup, ya dumb punks.

Early microcomputers did not have a single PCB with all the components on it. They were on separate cards, and all connected together via a bus. This was called a backplane and there were 2 types: active and passive. It didn't do anything except interconnect other components.

Then, with increasing integration, a main board with the main controller logic on it became common, but this had slots on it for other components that were too expensive to include. The pioneer was the Apple II, known affectionately as the Apple ][. The main board had the processor, RAM and glue logic. Cards provided facilities such as printer ports, an 80 column display, a disk controller and so on.

But unlike the older S100 bus and similar machines, these boards did nothing without the main board. So they were called daughter boards, and the one they plugged into was the motherboard.

Then came the Mac. This had no slots so there could be no daughterboards. Nothing plugged into it, not even RAM -- it accepted no expansions at all; therefore it made no sense to call it a motherboard.

It was not the only PCB in the computer, though. The original Mac, remember, had a 9" mono CRT built in. An analogue display, it needed analogue electronics to control it. These were on the Analog Board (because Americans can't spell.)

The board with the digital electronics on it -- the bits that did the computing, in other words the logic -- was the Logic Board.

2 main boards, not one. But neither was primary, neither had other subboards. So, logic board and analog board.

And it's stuck. There are no expansion slots on any modern Mac. They're all logic boards, *not* motherboards because they have no children.