Re: 68000 versus 8086
ULAs (Uncommitted Logic Arrays) were a UK innovation, mainly designed by Ferranti.
They allowed some of the layers of the wafers to be a common design, with the last few acting as a customization to get the chip to do what was needed. You could think of them as a half-way house to an FPGA, but with the configuration baked into the last few layers of silicon rather than after manufacturer.
I don't believe that any US company really bought into using ULAs, but they were used, as already pointed out, for the ZX81, BBC Micro, ZX Spectrum and Acorn Electron to reduce the chip count.
But production problems with ULAs were one of the main reasons why several of these systems were delivered late. Ferranti eventually disappeared into Marconi, which was sold off when that company went bust, so the technology disappeared.
Biting the hand that feeds IT
