http://www.bitsavers.org/components/sgs/_dataBooks/1985_SGS_Shortform_Catalog.pdf
Page 139... :o
Original GateArray for Amstrad. ;
Who will find the original programmer and software?
https://ethw.org/w/images/b/b0/Ref11_1987SGSShortformCatalog.1653458996.pdf
Gate arrays weren't programmed, the wires connecting the gates providing the desired functionality were manufactured on top of it.
Think of it as a piece of paper with a grid, and the 'program' as the thing you draw on that paper.
That is, if you could get an empty gate array, you'd only have an empty grid of gates. And I guess there were many different chips manufactured on top of that grid.
Yes, this is how it works in principle. So you can use the gatearray to cheaply manufacture your own logic chip. But it is not programmable at the customer side (e.g. Amstrad), but will get produced to order by the vendor.
It is massively cheaper, than creating a full chip (all the desing that needs to go into it). It is the same idea as of CPLDs and FPGAs. CPLDs were customer programmable logic devices (hence the name), but could only carry very low amount of logic (by far not enough for the GateArray). FPGA would have been what they would have used if they would have existed at the time ;-)