boot loader question

Bill Hacker wbh at
Tue Apr 5 01:32:28 PDT 2005

Joerg Sonnenberger wrote:

On Tue, Apr 05, 2005 at 05:22:49AM +0800, Bill Hacker wrote:

IBM chose the '8 *plus* 8 -1' route, joining the IRQ 2 and IRQ 9 pins 
together, and leaving us with a miserable few
IRQ's (several being hard-wired to the system).  No one would ever need 
any more IRQ's, right?

Actually you can't use more than 4+X IRQs on any PCI system, with X
being the number of SMP or timer interrupts, simple because PCI doesn't
allow more interrupts.
ACK.  Which is the *another* round of ignorant design.

How useful is that in a system with even six valid PCI slots
(one of mine) or an IBM p-series with 14 to 53 such slots?
Again - 'shared interrupts' have us going out in software and burning 
to inquire as to who wishes to do what, with which, and to whom each 
time one line goes active.

Were the INT lines to be read as a byte, or even a nibble, we could 
decode that
in a gate array and save a lot of time and code execution.

Same with drive devices.  Move one jumper on an 8" FDD, from unit select 
to radial select,
and the same cable and controller supported 16 drives instead of 4. 
SCSI-like, not IDE-like.

Designing for LCD consumer devices means Lybarger's Corrolary to Sod's 
Law applies here:

'All else being equal, you lose!'



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