The Pointer to PCI Data Structure is supposed to be two bytes. It is described in the PCI Firmware Specification Revision 3.0, section 5.1.1. PCI Expansion ROM Header Format.
The pointer is two bytes at 0x18. The pointer is supposed to be a multiple of 4 which means there's always at least two bytes of padding after the pointer. Some BIOS firmware images may use the 2 bytes following the pointer for other purposes (plus additional bytes before the PCI Data Structure) so we cannot assume the bytes will be zero.
Some PCI expansion ROMs may include both BIOS and Open Firmware images.
Fixed an issue where TBR doesn't have full 64-bit range. The original calculation was 64 bit and ended with a ÷ 10^9. This means the max for the upper 32 bits is 2^32/10^9 = 4. The solution is to use a multiplication method that supports a 96 bit product. core/mathutils.h contains functions for that. TBR driving frequency is assumed to be less than 1 GHz. Some minor modification is required for future > 1 GHz support.
Fixed an issue where get-msecs-601 and get-msecs-60x were not returning the same value. RTC was being calculated using timebase frequency instead of nanosecond frequency. 601 uses RTC. 60x uses TBR. On a real Mac, a G3 CPU won't have a RTC and accessing RTC would cause an exception. This is not the case for dingusppc but I don't think that's a problem.
Fixed an issue where RTC was not being updated if only the upper 32 bits (seconds) was read.
Also simplified things by always updating the timestamp instead of only when the seconds changes.
Fixed an issue where the following would cause inconsistent results (tb in the left column would sometimes decrement instead of always incrementing):
2 0 do 2 0 do cr tb@ 8 u.r ." ." 8 u.r loop 2 0 do cr 12 spaces rtc@ 8 u.r ." ." 8 u.r loop 2 0 do cr tb@ 8 u.r ." ." 8 u.r space rtc@ 8 u.r ." ." 8 u.r loop loop
RTC and TBR could not be used simultaneously because they are both incremented by an amount based on the last time stamp but that time stamp can be changed by accessing either RTC or TBR. The solution is to have a different time stamp for each.
