8100 has extra pins on both ports, 840av only on one port. I suspect they were worrying about people plugging ADB into the ports so made them different, but couldn't make up their mind. Plus decided to use the pins for something.My Power Mac 8600 has those 3 extra pins on the S-Video input. The S-Video output just has 4 pins (like ADB).
Some Macs have the extra pins on both ports? Some Macs have a composite output pin on the S-Video output? Some Macs don't have S-Video output.
They must accept ADB because it's the same connector as S-Video.I suspect they were worrying about people plugging ADB into the ports so made them different, but couldn't make up their mind.
Your screenshot says Phillips serial bus. I suppose there's some Phillips specs that describes this I2C interface and what it would be used for in this S-Video input context - probably to control the video equipment that is sending the video signal to the S-Video input - maybe play/pause/input select/channel select etc.Plus decided to use the pins for something.
The image of the backside of the 8500 from wikipedia (linked above) shows the same S-Video connectors as my 8600.The 8600 should have the I2C pins. It doesn't mention it the Dev Notes, but it does in the 8500, and they're close enough to the same that they wouldn't have removed the feature.
Yes, but if they add pins, they don't look the same.They must accept ADB because it's the same connector as S-Video.
It's because Phillips invented I2C, they're just being a bit formal in their description.Your screenshot says Phillips serial bus. I suppose there's some Phillips specs that describes this I2C interface and what it would be used for in this S-Video input context - probably to control the video equipment that is sending the video signal to the S-Video input - maybe play/pause/input select/channel select etc.
Yeah, if you go further back the RTC was controlled by bit banged I2C from the VIA chip on the SE and I assume earlier macs.I2C is used a lot in Macs, but Apple didn't really talk about it ever. The DFAC and DFAC-II sound chips both are controlled via I2C, including for the system volume. The Mac TV and Quadra AVs used it to control the Philips video input chips, and the Mac TV also used it to interface to the IR remote control reader. The beige G3 and all later PowerMacs also use the I2C bus to read the DIMM serial presence detect information so they can auto-configure, and both of those machines also can use VESA DDC/EDID to read the monitor info, which is I2C once again. (Yes, the iMac's internal monitor returns valid DDC/EDID information).
The I2C bus master is usually Egret or Cuda. Egret and Cuda 2.x bit-bang it in software, while CudaLite and the short-lived Cuda 3 had a hardware implementation. Motorola calls it something else to dodge Phillips' trademarks, but that's clearly what it is (CudaLite/Cuda 3 are the publicly-sold 68HC05E5 with Apple's software burned into the internal ROM, so you can easily find the datasheet/programming manual). PG&E handles it in PowerBooks, again with hardware assist.