poking at the broken timer interrupt handler again

boot.subx

@@ -302,7 +302,7 @@ idt_start:
 # https://wiki.osdev.org/index.php?title=Interrupts&oldid=25102#Default_PC_Interrupt_Vector_Assignment
 
 # entry 8: https://wiki.osdev.org/Programmable_Interval_Timer
-  timer-interrupt-handler/imm16  # target[0:16]
+  null-interrupt-handler/imm16  # target[0:16]
   8/imm16  # segment selector (gdt_code)
   00  # unused
   8e  # 1/p 00/dpl 0 1110/type/32-bit-interrupt-gate
@@ -360,24 +360,6 @@ $null-interrupt-handler:epilogue:
   fb/enable-interrupts
   cf/return-from-interrupt
 
-timer-interrupt-handler:
-  # prologue
-  # Don't disable interrupts; the timer has the highest priority anyway,
-  # and this interrupt triggers extremely frequently.
-  fa/disable-interrupts
-  60/push-all-registers
-  9c/push-flags
-  # acknowledge interrupt
-  b0/copy-to-al 0x20/imm8
-  e6/write-al-into-port 0x20/imm8
-  31/xor %eax 0/r32/eax
-$timer-interrupt-handler:epilogue:
-  # epilogue
-  9d/pop-flags
-  61/pop-all-registers
-  fb/enable-interrupts
-  cf/return-from-interrupt
-
 keyboard-interrupt-handler:
   # prologue
   fa/disable-interrupts