| ---------- | - | ---------- |
| P64-prefix | rsvd | P48-Prefix |
-When Twin-SVP Mode is enabled (0b11), a *second* P48-P64 prefix pair follows
-in the VBLOCK, which applies vector-context from the *second* instruction's
-registers.
+When Twin-SVP Mode is enabled (0b11), a *second* P48 prefix follows after a P48-P64 pair,
+in the VBLOCK (another 16 bits after the 32 bit P48/P64 block), which applies vector-context from the *second* instruction's
+registers. The reason why Twin-SVP's prefix is only P48 is because P64 can change VL and MVL. It makes no srnse to try to reset VL/MVL twice in succession.
+
+VL/MVL from a P64 prefix is applied as if a [[SV.SETVL]] instruction had been executed as a hidden (first, implicit) instruction in the VBLOCK.
# Rules