RSP VSAW

[bryanperris]

The VSAR/VSAW instruction is not fully explained in the RSP official doc, but it clearly shows that the vector source is always written into the accumulator after the read part.

If I follow what the doc describes, the test fails, however if the accumulator is always written into the vector source before VSAW is executed then everything passes. This possible fact would mean VSAW is useless.

A test would be useful if it can show the vector register states after called VSAR and see if the vector source is indeed changed.

In the RSP graphics ucode, vsar is used where the same vector register is selected for vd, vs, vt, which clearly shows that they don't intend to change what is in the accumulator, only read from it.