It is very hard to estimate the relative speed of a mov-only CPU (with a jump at the end of the program). The mov-only restriction applies only to how a program is input into the machine, it does not restrict the CPU architecture in any way. Obviously, the CPU would first analyze the whole mov-only program and convert it into something that is closer to x86 instructions: arithmetic instructions, unconditional jumps, conditional jumps. The success of this procedure, and ultimately the execution speed, depends on how many mov-patterns the CPU can recognize.

Compilers would need to produce code that consists of standardized mov-only code patterns. This would help keep the CPU architectures relatively simple.

Coming very close to native x86 performance seems possible, at least in theory.