Re: Re: A86: Questions on Port 3, calc on, off, APD, etc
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Re: Re: A86: Questions on Port 3, calc on, off, APD, etc
I don't know what book he was refering to, but I have read several on the
subject. Two that stand out are Peter Norton's Inside the PC, and The
Peter Norton PC Programming Bible. These books have much info on the Intel
based PC:
Interrupt 2 on the PC, which has 256 vectored software interrupts, is the
NMI interrupt. This NMI bypasses the regular PIC interrupt controller. It
is used by the hardware to signal that memory has not been refreshed or is
otherwise corrupted. It is normally tied to a BIOS routine that gives a
"PARITY ERROR" message, then halts the computer. I've seen this on my old
8088 based IBM PC immediately after pulling the memory expansion card; I'd
forgotten to turn off the computer first. It also occurs when a device
conflicts with memory--like a game controller card.
On IBM PS/2 systems, with Microchannel architecture, there is a Timer Mode
3 (0-2 are on all PC's) that is also tied to the NMI. It can be used by
the operating system as a watchdog to make sure a task like a timer tick
handler doesn't take too long and crash the entire system, since most ISR's
cannot be re-entered.
But since this doesn't have much to do with A86 programming, I'll let you
read the books for yourselves.
At 06:38 PM 5/29/98 EDT, ComAsYuAre@aol.com wrote:
>
>
>In a message dated 5/29/98 12:52:54, you wrote:
>
>>I remember reading in a x86 ASM book that the NMI on Intel processors was
>used
>>for some kind of hardware error (memory corruption?)
>
>
>what book are you referring to?
>
>
// David Phillips
// mailto:electrum@tfs.net
// AIM: electrum32
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