How many two 8259A can connect interrupt sources?

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leetow2003
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How many two 8259A can connect interrupt sources?

Post by leetow2003 »

One 8259A can connect 8 interrupt sources,
the IRQ2 in master 8259A must connect to slave 8259A,
I think two 8259A can connect 7+8 interrupt sources,
but I find some books say two 8259A can connect
8+8 interrupt sources,I want to know how many?
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qw
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Re: How many two 8259A can connect interrupt sources?

Post by qw »

Technically, one can attach 8 slave PIC's to one master PIC, resulting in 64 distinct IRQ lines. It's never been done as far as I know.
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rdos
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Re: How many two 8259A can connect interrupt sources?

Post by rdos »

The PIC is all legacy, and all modern computers have an APIC (and some PCI-cards even use MSI to directly generate processor interrupts). Some modern computers still have legacy-PICs as well, but then typically won't support non-legacy devices through PIC.
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