I/O probeing at Win XP startup?

Microsoft Windows xp professional w/serv...
February 2, 2010 at 23:12:38
Specs: Windows XP
We have an ISA-board that seems to be addressed at a very early point in the Windows startup sequence. The board uses the I/O address space 0x340 - 0x35F. Does Win XP probe I/O addresses at startup? What are the board supposed to answer? Is the probeing configurable?

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#1
February 3, 2010 at 02:29:04
Of course windows addresses the motherboard at an early point in windows startup. Thats what windows does, acts an an interface between hardware and software.

The board uses lots of I/O addresses, hundreds of them. Every piece of hardware has its own I/O address. It is the BIOS that reads theses I/O addresses and passes them onto Windows. The BIOS does this even before Windows has started to load.

Stuart


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#2
February 3, 2010 at 03:45:17
The address space for the board has been reserved in BIOS and the board driver is not yet running. Still there seems to be some very early part of Windows that sends addresses whithin the address space of the board on the ISA-bus. Therefore I wonder if there is a probe mechanism in Windows and if it is configurable?

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#3
February 3, 2010 at 04:31:13
Windows doesn't send anything to the board. It reads the addresses that are set by the BIOS. Some of them are configurable via device manager but most are per-configured by the hardware itself and you are stuck with what you get.

There are huge swathes of memory set aside for I/O addressing. Most of this is controlled by the BIOS (Basic Input Output System) and the hardware. This is why you will never have much more than 3.2 Mbs RAM available to Windows XP although there may be 4 Mbs installed and the CPU is capable of addressing 4Mbs. The rest is used for I/O addressing.

Stuart


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#4
February 3, 2010 at 04:53:52

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