[lallysingh]

AFAIK, the FPU was a stack calculator. So you pushed things on and ran calculations on the stack. https://en.wikibooks.org/wiki/X86_Assembly/Floating_Point

[Sesse__]

It's only a stack machine in front, really. Behind-the-scenes, it's probably just eight registers (the stack is a fixed size, it doesn't spill to memory or anything).

[lallysingh]

Definitely was 8 regs: https://intranetssn.github.io/www.ssn.net/twiki/pub/CseIntra... also where you'd see 'long double'