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geekhack Community => Keyboards => Topic started by: PortablePlatypus on Wed, 03 September 2014, 03:34:35

Title: Switch on back of keyboard?
Post by: PortablePlatypus on Wed, 03 September 2014, 03:34:35

http://www.ebay.com/itm/261579910636 this acer of mine has a switch on the back. For some reason I can only get it to work on 2. I'm assuming that's normal, but I'm wondering what exactly it is for.

Title: Re: Switch on back of keyboard?
Post by: rowdy on Wed, 03 September 2014, 06:00:34

I'm guessing maybe it switches the keyboard between AT, XT and something else?

Title: Re: Switch on back of keyboard?
Post by: Findecanor on Wed, 03 September 2014, 06:56:38

I'm guessing that they are 1, 2 and 3 for XT AT(PS/2) and Terminal respectively.

The three are the same protocol at the lower levels, with the key codes and some behavioural details being different. The key code sets are internally numbered 1, 2  and 3.
There was a time when Microsoft wanted to transcend to using set 3 (Terminal) for Windows NT, but it didn't take off. I think the reason could have been that some popular non-IBM keyboards did not behave properly in set 3.

Title: Re: Switch on back of keyboard?
Post by: Daniel Beardsmore on Wed, 03 September 2014, 16:33:32

Quote from: Findecanor on Wed, 03 September 2014, 06:56:38

I'm guessing that they are 1, 2 and 3 for XT AT(PS/2) and Terminal respectively.

The three are the same protocol at the lower levels, with the key codes and some behavioural details being different.

XT and AT are fairly different:

http://www.cs.cmu.edu/~jmcm/info/key2.txt

Then again, that page says that people use set 3, and everyone else says people use set 2 …