Competing RISC designs tanked for a number of reasons, but not just because Intel and AMD started pumping money into their products. RISC vendors were in the b

Competing RISC designs tanked for a number of reasons, but not just because Intel and AMD started pumping money into their products. RISC vendors were in the business of selling hi-end workstations and servers that required their own respective RISC CPU's, which meant that each vendor had its own, in-house CPU design arm and either their own fab or they outsourced the CPU manufacturing to someone else. In a way, the RISC CPU was a by-product of what they sold but never the product they sold alone. Two problems followed. The CPU design is an expensive process, and keeping one's own fabs up to date with the latest and greatest manufacturing process is even more expensive, especially as the designs and processes advanced. It eventually became prohibitively expensive to maintain one's own fab, and RISC vendors started falling behind the bleeding edge (DEC, Motorola, etc.). IBM managed to get away with it for a time, but eventually, they also divested. The second problem concerned the outsourcing of the CPU manufacturing. Those RISC vendors (e.g. SGI with their MIPS) who did not have their own fabs had to contract a fab (e.g. NEC). Such a fab would produce a diverse range of microchip products, and a CPU would be just one of them. Which typically meant not the latest and greatest process, but at least a generation behind. Whereas both Intel and AMD were dedicated CPU design and manufacturing houses (although AMD also divested their fabs later), so they could specifically focus on what mattered for CPU's and for CPU's only. That said, for Intel and AMD, the CPU was the product, whereas for the RISC vendors, it was not, however important, the CPU was for them.