BIOS Overview
30 product description
DMA Channel Controllers
Only “I/O-to-memory” and “memory-to-I/O” transfers are allowed. “I/O-to-I/O” and “memory-to-memory”
transfers are disallowed by the hardware configuration.
The system controller supports seven DMA channels, each with a page register used to extend the
addressing range of the channel to 16 MB. The following table summarizes how the DMA channels are
allocated.
I/O Address Ports Function
0000 - 000F DMA controller 1
0020 - 0021 Master interrupt controller (8259)
002E - 002F NS364 Configuration registers
0040 - 0043 Timer 1
0060, 0064 Keyboard controller (reset, slow A20)
0061 Port B (speaker, NMI status and control)
0070 Bit 7: NMI mask register
0070 - 0071 RTC and CMOS data
0080 Manufacturing port (POST card)
0081 - 0083, 008F DMA low page register
0092 PS/2 reset and Fast A20
00A0 - 00A1 Slave interrupt controller
00C0 - 00DF DMA controller 2
00F0 - 00FF Co-processor error
0170 - 0177 IDE secondary channel
01F0 - 01F7 IDE primary channel
0278 - 027F LPT 2
02E8 - 02EF Serial port 4 (COM4)
02F8 - 02FF Serial port 2 (COM2)
0372 - 0377 IDE secondary channel, secondary floppy disk drive
0378 - 037A LPT1
03B0 - 03DF VGA
03E8 - 03EF COM3
03F0h- 03F5 Floppy disk drive controller
03F6 IDE primary channel
03F7 Floppy disk drive controller
03F8 - 03FF COM1
04D0 - 04D1 Interrupt edge/level control
0678 - 067B LPT2 ECP
0778 - 077B LPT1 ECP
0CF8 - 0CFF PCI configuration space
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