COTS stands for Commercial Off-The-Shelf and means any component that is freely available and/or well-documented.
IC
Especially in Integrated Circuit (IC) chips, it is the contrary to ASIC, "Application-Specific IC" that are custom-built. COTS components normally are mass-produced in higher numbers and, therefore, cost-effective.
As supply chains for chip manufacture were all out-sourced to South East Asia, where Red China uses massive government subsidies and workers live in barracks, many former chip manufacturers in the EU/USA went out of business as customers (like "Apple") discontinued their domestic-built manufacture and relocated to Red China. This makes costs for creating ASIC chips much more prohibitive, reserving it to the biggest companies; many chip designers (ARM Assoc., ex-Acorn) now are "No-Fab", meaning they just sell the designs and specifications to other companies.
CPLD and FPGA re-programmable chips have alleviated this, so designers can use IPs or "Softcores", Instruction set Processors, to attain ASIC capabilities; as reprogrammable chips now are available to the hobbyist market, discontinued chips can be simulated by those chips.
CPC
The Amstrad CPC does not make heavy use of ASICs; the MSX series, however, holds the pole-position as it is exclusively constructed using COTS component so many manufacturers could build them. Commodore, instead, acquired MOS technologies and relied heavily on ASIC chips for all their product lines apart from the IBM PC/XT/AT-compatibles.
The CPC uses those COTS chips:
- Zilog Z80 CPU
- General Instruments AY-3-8912 PSG, also built by Yamaha as the Ym2149, as sound chip (also used in the MSX platform)
- Motorola 6845 CRTC; however, the different manufactures use by Amstrad cause incompatibilities, and it was combined to a Gate Array ASIC. In later generations (cost-down CPC and CPD+), this chip was integrated into an Amstrad ASIC.
- NEC 765 FDC as Floppy controller
- NEC 8255 PPI chip as Programmable Peripheral Interface (PIO)