New answers tagged serial
13
Well, this is to be expected; the BIOS Data Area has only four slots for I/O addresses of serial ports, with slots for parallel ports immediately following. In the MEMORY.LST file from Ralf Brown’s, we can find the following entries0:
MEM 0040h:0000h - BASE I/O ADDRESS OF FIRST SERIAL I/O PORT
MEM 0040h:0002h - BASE I/O ADDRESS OF SECOND SERIAL I/O PORT
...
13
The BIOS list only contains addresses of up to four standard 8250-type COM ports found at boot at the standard addresses.
It will not contain more than four ports, it will not contain any non-8250 type COM ports, and COM ports at non-standard addresses, such as PCIE COM ports, and USB COM ports which don't have an IO address to begin with. It will not ...
6
The BIOS data area only has room for addresses of four com ports, at 40:00 through 40:07.
More serial ports would be driven by some device driver with some other place to store the address(es) and IRQ(s).
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