diff --git a/src/cpu.c b/src/cpu.c
index 64a9702..1e62d9b 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -520,7 +520,10 @@ void cpu_set()
   
         isa_cycles = cpu_s->atclk_div;      
         
-        cpu_rom_prefetch_cycles = cpu_s->rspeed / 1000000;
+        if (cpu_s->rspeed <= 8000000)
+                cpu_rom_prefetch_cycles = cpu_mem_prefetch_cycles;
+        else
+                cpu_rom_prefetch_cycles = cpu_s->rspeed / 1000000;
 
         if (cpu_s->pci_speed)
         {
@@ -1680,6 +1683,8 @@ void cpu_update_waitstates()
         if (is486)
                 cpu_prefetch_cycles *= 4;
         cpu_mem_prefetch_cycles = cpu_prefetch_cycles;
+        if (cpu_s->rspeed <= 8000000)
+                cpu_rom_prefetch_cycles = cpu_mem_prefetch_cycles;
 }
 
 void cpu_set_turbo(int turbo)