Talk:RAMBO-1

As for the 2mb PRG, I'm not sure if the cart actually supports that much ROM, but the PRG registers apparently are 8 bits, and 8kb * $100 = 2048kb = 2mb. --Drag 03:05, 9 November 2011 (UTC)

Alternate IRQ timing

This is how to get 4 games working: Klax, Skull&Crossbones, Rolling Thunder and Hard Drivin'.

• Address mask: $E001.

writes to $C000: irq_flags|=2; irq_latch=data;
writes to $C001: irq_flags|=1; irq_mode=data&1;
writes to $E000: irq_enable=false; IRQ acknowledge by CPU.
writes to $E001: irq_enable=true; IRQ acknowledge by CPU.

• When the IRQ is clocked by CPU or scanline modes:

If irq_flags&1:
   irq_counter = irq_latch;
   if irq_latch != 0
   {
      if irq_flags&2 irq_counter |= 1;
      else irq_counter+=1;
   }
   irq_flags=0;
Else if irq_counter == 0:
   irq_counter = irq_latch;
Else
   irq_counter--;
If irq_counter == 0 and irq_enable == true
   irq_delay=4 (IRQ will be fired 4 CPU cycles later)

--Zepper (talk) 20:12, 7 August 2017 (MDT)