FLAME ABOUT STUPID INTERRUPT SYSTEM DESIGNERS (partial apology)

[John M. Haugen]

In article <9005282014.aa08953 at PARIS.ICS.UCI.EDU>, baxter at zola.ICS.UCI.EDU (Ira Baxter) writes:
. . .
> Given all that... has anybody made the ISC 2.0.2 X5 ASY update operate
> with more than one device on the same interrupt level?  The docs
> explicitly say that some serial ports really do allow multiple devices

Yes IBM goofed in their first attempt at the bus (ISA) by not allowing shared
interrupts. But there second attempt (Microchannel) does.  Also I believe that
the interrupts on the ISA bus are edge triggered.  It would be hard to share
interrupts that are edge triggered.  Microchannel is level sensitive.  That is
the interrupt line is not dropped until the card driving the interrupt is
referenced by reading or writing to it's I/O registers.  That would make it
much easier to share interrupts.

> IDB
> (714) 856-6693  ICS Dept/ UC Irvine, Irvine CA 92717

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