I/O addresses

[DT2PAAG]

I am studying for my A+ and don't understand where these addresses are located. They are in memory, but what memory, RAM?

[YODA74]

To communicate with the computer, any I/O device needs to have an address so that the computer can write to it and read from it. For this purpose many I/O devices (such as serial ports) use a special type of address known as an I/O addresses (sometimes called an I/O port). It's actually a range of addresses and the lower address in this range is the base address. If someone only says (or writes) "address" it likely really means "base address"

Instead of using I/O, addresses some I/O devices read and write directly from/to main memory. This provides more bandwidth since the conventional serial I/O system only moves a byte at a time. There are various ways to read/write directly to main memory. One way is called shared memory I/O (where the shared memory is usually on the same card as the I/O device). Other methods are DMA (direct memory access) on the ISA bus and what is about the same as DMA (only much faster): "bus mastering" on the PCI bus. These methods are a lot faster than those used for the serial port. Thus the conventional serial port with its interrupt driven (every 14 bytes) interface and single bytes transfers on a bus which could accommodate 4 (or 8) bytes at a time is not suited for very high speed I/O.

I'm sure you've read all this before also search the knowledge base here at the PC Guide it will have a lot more info.

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Death has come to our windows.

-- Jeremiah 9:21
(undoubtedly a Biblical reference to a Microsoft product!)

YODA74@carolina.rr.com