Re: Quadra 950: System clock <--> Hardware clock questions
On Sun, 2003-03-02 at 06:19, Brad Boyer wrote:
> On Sat, Mar 01, 2003 at 06:57:11PM -0500, Hank wrote:
> > I guess have a couple of questions? How does the system clock keep time
> > if it does not
> > use the hardware clock?
> The system clock is tied to the timer interrupt. Reading the hardware
> clock is too expensive in terms of time to do regularly.
> > What exactly is the problem with the 900 series? Why can't the system
> > clock copy itself
> > to the hardware clock during shutdown and reboot?
> I suspect that there's a bug in the hwclock routines in the kernel. It
> decides how to read the actual hardware clock based on what ADB controller
> the machine has, since on most Macs it is actually accessed through the
> ADB routines. This means that it tries to treat the Q900 and Q950 like
> the IIfx, but I suspect that it while it's right on the IIfx, the Q900
> and Q950 actually need a different access method. It's been a problem
> as long as I've been involved, and noone has ever cared to fix it since
> as far as I know, those two models are the only ones that work at all
> but don't have hwclock support working. I have a IIfx, so I know it
> works, but I don't have a Q900 or Q950.
> Brad Boyer
I know that I'm replying to a very old posting, but I recently dug into
this problem and have some insight. Brad was correct, the Q900 and Q950
have different hardware for accessing the hardware clock. These units
have a custom IC that Apple calls 'Caboose'. This chip handles the
clock, PRAM and the key-switch. I haven't been able to find any specs
or info on accessing this chip. My TODO list now includes dumping the
Q900 and Q950 ROMS and attempting to locate some clues on accessing the
Caboose. Perhaps someone with more experience disassembling Mac ROMs
would be interested in helping?