Subject: Re: malloc above splimp
To: Ethan Dicks < (Ethan Dicks)>
From: None <>
List: amiga-dev
Date: 09/01/1994 18:31:28
> > Chris> If its do to interrupts from the IO bridge, is it possible to
> > Chris> use interrupt level 2 instead?  This is the level that IO
> > Chris> should take place at not level 6.  Interrupt level 6 is
> > Chris> reserved for system clocks and other things (?) of such high
> > Chris> importance.
> > 
> While I did not design the GG2, I do currently manufacture it.  AFAIK, the
> reason that David Salamon designed the card to use INT6 is that under
> AmigaDOS, it's the Right Thing.  I can certainly understand how people might
> want an INT2-interrupting board, but consider that the GG2 might be asked to
> handle interrupts from an IDE hard disk, an Ethernet card and a couple of
> high-speed serial ports.  This is all do-able inside an A4000 with two ISA
> cards.

I am willing to say that I have done no benchmarks, so if you have then
I will drop this :)

However, all the things you mentioned are IO based devices.  You can have
20 of them on this bridge if you want, I claim that it should still be
interrupt level 2 and not 6.

The point is that no IO device should be interrupting at level 6 unless its
totaly critical.  I have always seen this as a way of working around either
1) bad hardware (of which I admit many ISA fall claim to) or 2) bad software.

In both cases the reason for using level 6 is oxymoronic the software/hardware
is poorly written so it uses level 6 for speed and thus wastes time in
the most critical level of the system.

Would you rather have your audio sample mess up or your video/animation?
Or would you rather wait a short time to get the next datum from the IO device?

IO devices (fair to good ones) are designed to handle small pauses.  This is
becuase they are never considered as time critical as other devices.  Realize
that nothing under amigados is happening when *any* interrupt is pending
except interrupt processing.  So what if 300 bytes of interrupt code gets to
execute above you..

Just my opinion, of which I have no benchmarks to back up. :)