What are the roots to the 18x8 matrix?

[Topre]

Most keyboards, especially full-sized keyboards has an 18x8 matrix. Why was this? Is it not more efficient to have a 11x10 matrix for 104 keyboards, or a 12x12 for 144 key keyboards? There are no keyboards that I know of that actually has an 18x8 gird when you look at the keys, however it seems as if the 18x8 matrix is a standard. When tracing matrices of CST104 keyboards, it seems like the most of the modifiers has it's own column, or in some cases shares a column with another less commonly used key. Each Windows key has it's own column. Both of the shift-keys share the same column alone. Both control-keys share a column with F5 and Pause/Break. Both Alt-keys share a column with Print Screen and Scroll Lock. It seems like the doing this will make NKRO easier, or at least have KRO + modifiers for no ghosting. So was the 18x8 matrix related to ghosting issues, or was it completely something else?

[Hak Foo]

NKRO is equally easy regardless of layout.

However, if you're limited to 2KRO, you might benefit from some layout compromises that ensure, say, control-alt-delete, will be trackable.

[Topre]

Yea, I figured the matrix had nothing much to do with NKRO, but 2KRO or similar does seem possible. But it just seems weird to pick 18x8 to be a standard out of all those possible combinations such as 16x8 or 12x11 for 122-key or less keyboards. Or using a matrix that does not take up as many traces as the 18x8 matrix.

[Zustiur]

Don't forget that computer keyboards inherited a lot from typewriters and electric typewriters. You may have to look further back for your justification.
It stands to reason that electric typewriters followed the same key layout as their mechanical forebears. Why should a computer keyboard be any different? It's just a glorified typewriter... and a calculator. It's a calculator too, so lets tack one of those on ... hmm where to put it. I guess just to the side of the keyboard makes sense, it's the same basic number of rows... Everyone's right handed aren't they, so we'll put it on the right hand side...  <-- This is how I imagine it went. For the record, I'm left handed

What puzzles me more is where the Page Up Page Down cluster came from ... and what is that cluster even called anyway?

[dorkvader]

For some keyboards, it makes a difference. From what (little) I know about capacitive matricies, the way IBM did their matrix is easier than a 12*12, what with all the sense / scan lines. For most regular keyboards I imagine it can't make too much of a difference, but it's probably easier to program the way they did it.

Another option is that it'd be much easier to lay out the traces that way. With a matrix that's different than your key configuration, it would start to get very difficult indeed to get it working on your PCB. In the olden days, you didn't have a computer to route your PCB lines, and in the modern era, the PCB is often one-sided. In both cases, you only have so much room for your traces (unless you use super thin traces like vortex)

Zustiur, I think that might be called the nav cluster, but I'm not sure on that.

[Topre]

I don't think typewriters have what we would call matrices, but not sure about electrical typewriters.

[davkol]

Don't forget that computer keyboards inherited a lot from typewriters and electric typewriters. You may have to look further back for your justification.
It stands to reason that electric typewriters followed the same key layout as their mechanical forebears. Why should a computer keyboard be any different? It's just a glorified typewriter... and a calculator. It's a calculator too, so lets tack one of those on ... hmm where to put it. I guess just to the side of the keyboard makes sense, it's the same basic number of rows... Everyone's right handed aren't they, so we'll put it on the right hand side...  <-- This is how I imagine it went. For the record, I'm left handed

What puzzles me more is where the Page Up Page Down cluster came from ... and what is that cluster even called anyway?

Theoretically, they could go with matrix layout, but the [enterprise] market demanded something else.