🚀 go-pugleaf

I am attempting to do some performance predictions, for native PowerPC 
assembler code running on a PowerMAC 6100/66

Unfortunately, I know next to nothing about the System 7.5 operating
system I am sitting on, and the overheads it introduces. Any help with
some of the following questions would be much appreciated.

Whilst running a piece of code that simply loops and reads memory
I notice that the timer at the top of the screen freezes, however
I would assume that asynchronous timer ticks (interrupts) are still
occuring.

so :

How often does a timer interrupt occur on a 6100/66 ?

How much work is done in the timer interrupt handler, specifically :
a) How long is spent in the timer handler (microseconds) and
b) How much code and data (in Kb) is called into the cache as
     part of this handler. 
c) Do chained interrupt handlers get called ?

Are there any other asynchronous system events occuring....I know
that moving the mouse causes interrupts, but are there any others,
such a disk management interrupts ? (This particular machine is not
networked, so no comms interrupts occur)

What is the bus speed of this particular machine ? Is it the same as
the processor ? (I don't have the reference manual :( either )

Any help will be much appreciated....even if it is just pointing me toward
a good book to read.

Regards

Nic