Differences

This shows you the differences between two versions of the page.

--- wswan:guide:optimization_v30mz [2024/02/17 20:10] – asie
+++ wswan:guide:optimization_v30mz [2025/12/31 12:35] (current) – removed asie
@@ Line 1: / Line 1: @@
-====== Optimizing for the NEC V30MZ CPU ======
-While the V30MZ is an 80186-compatible CPU, its instruction timings differ wildly from common expectations and are more reflective of its 1990s-era design:
-  * ''MUL'' is very fast on this CPU, taking 3-4 cycles. As a result, "shift plus add" ladders will almost always be equal in performance on slower.
-  * Using ''XCHG'' over ''PUSH/POP'' (and ''XCHG AX, reg'' over ''MOV AX, reg'') is a popular pattern on the 8088/8086 due to the speed benefit. However, on the V30MZ, that is not the case:
-    * ''XCHG'' on V30MZ always takes 3 cycles.
-    * ''PUSH'' and ''POP'' take 1 cycle each for general registers. This means that ''PUSH/POP'' will be one cycle faster.
-    * While ''MOV AX, reg'' is one byte larger than ''XCHG AX, reg'', it also only takes 1 cycle.
-  * ''XLAT'' takes 5 cycles. Many simple CPU operations (such as ''SHR reg, 4'' or ''MUL reg'' - both taking 3 cycles) can actually be faster!
-TODO: Expand this list.