> some customers insisted on a 'second source' for cpus

IBM required it. It was their business MO to protect themselves from losing access to a technology or having the market be dictated by one company. Intel acquiesced so that they would be the architecture of the IBM PC-series.

Afaik they could implement the ISA but not the Intel interconnect bus so AMD licensed Hypertransport (as used in the Alpha) from DEC so you had different motherboards/chipsets.

All second source AMD (and other manufacturer) chips were pin-compatible with Intel chips. Compare the i386/am386, the i486/am486, etc. Even a few non-second source (e.g. the unique uArchs that came later) designs were still pin-compatible, such as the 5x86 and K6/K6-II/K6-III. In fact, the third parties were the first to break away from electrical compatibility with their Super Socket 7 motherboards.

Intel did change sockets as a means to disallow socket-compatibility; forcing consumers into their architecture if they bought their motherboard, but that had no effect on AMD's development. AMD had purchased a significant share of DEC's engineering portfolio and, along with it, their employees. Those employees then developed the K7 (Athlon) architecture around some of the Alpha's technological advantages, which included HyperTransport, a multi-issue FPU (fixing one of the major issues AMD had struggled with and bringing them ahead of Intel), etc.

Those cross licenses are the only reason why this laptop isn't running on Itanium, without them there wouldn't exist AMD64.

The 'only' reasons (plural) that your laptop does not run Itanium: - battery life: an Itanium in a laptop would run for less than an your - too hot: Itanium servers ran incredibly hot due to power. A laptop would probably catch fire in short order - Windows was not supported on Itanium - cost: would you pay $5K for an Itanium laptop?

some customers? I heard it was IBM.