Gate Array is one of the typical method of producing an LSI chip in ASIC.
Gate-arrayed boards are already made and sold, which en engineer is only to buy.
Just as named gate-arrayed board is a certain size of board on which transistors, as much as millions, are arrayed like on a chessboard.
A unit as this is already made and arranged.
An engineer only draws wire, as he like, among those units.
It enables a rapid development. To complete the product in a day is not impossible. Usually, it will take a month or so to produce a typical type of LSI.
On the other hands, it will cost much and performance of the product is low, and power-consuming.
Assume one is in a dead hurry to make up 2-input NAND, which requires 4 transistors.
He would buy a gate-arrayed board with 10 millions of it.
Only a small area of the product would be actually used.
This would waste size, money, power, but earn only time.
Now this gate-array processing is rarely used.
The rare example is a few basic access points of NTT handy phones, our professor says.