Being the ouput of cat proc/ioports:
0000-001f : dma1
0020-0021 : pic1
0040-0043 : timer0
0050-0053 : timer1
0060-0060 : keyboard
0064-0064 : keyboard
0070-0071 : rtc0
0080-008f : dma page reg
00a0-00a1 : pic2
00c0-00df : dma2
00f0-00ff : fpu
0170-0177 : 0000:00:0f.1
0170-0177 : pata_via
01f0-01f7 : 0000:00:0f.1
01f0-01f7 : pata_via
0290-0297 : pnp 00:07
02f8-02ff : serial
0376-0376 : 0000:00:0f.1
0376-0376 : pata_via
0378-037a : parport0
037b-037f : parport0
03e0-03e7 : pnp 00:08
03f2-03f2 : floppy
03f4-03f5 : floppy
03f6-03f6 : 0000:00:0f.1
03f6-03f6 : pata_via
03f7-03f7 : floppy
0400-041f : pnp 00:08
0400-0407 : vt596_smbus
04d0-04d1 : pnp 00:08
0778-077a : parport0
0800-087f : pnp 00:08
0800-0803 : ACPI PM1a_EVT_BLK
0804-0805 : ACPI PM1a_CNT_BLK
0808-080b : ACPI PM_TMR
0810-0815 : ACPI CPU throttle
0820-0823 : ACPI GPE0_BLK
0cf8-0cff : PCI conf1
d000-d0ff : 0000:00:11.5
d000-d0ff : VIA8237
d400-d41f : 0000:00:10.3
d400-d41f : uhci_hcd
d480-d49f : 0000:00:10.2
d480-d49f : uhci_hcd
d800-d81f : 0000:00:10.1
d800-d81f : uhci_hcd
d880-d89f : 0000:00:10.0
and the output of cat /proc/iomem:
00000000-0000ffff : reserved
00010000-0009fbff : System RAM
0009fc00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000cf7ff : Video ROM
000e0000-000fffff : reserved
000f0000-000fffff : System ROM
00100000-bffbffff : System RAM
01000000-01538f03 : Kernel code
01538f04-017c217f : Kernel data
01877000-0194dfff : Kernel bss
bffc0000-bffcdfff : ACPI Tables
bffce000-bffeffff : ACPI Non-volatile Storage
bfff0000-bfffffff : reserved
cff00000-dfefffff : PCI Bus 0000:01
d0000000-d7ffffff : 0000:01:00.0
e0000000-efffffff : PCI MMCONFIG 0000 [bus 00-ff]
e0000000-efffffff : pnp 00:0d
f0000000-f7ffffff : 0000:00:00.0
fca00000-feafffff : PCI Bus 0000:01
fd000000-fdffffff : 0000:01:00.0
feae0000-feafffff : 0000:01:00.0
febc0000-febdffff : 0000:00:0d.0
febc0000-febdffff : e1000
febf0000-febf7fff : 0000:00:0a.0
febf0000-febf7fff : 0000:00:0a.0
febfbc00-febfbcff : 0000:00:10.4
febfbc00-febfbcff : ehci_hcd
fec00000-fec00fff : reserved
fec00000-fec003ff : IOAPIC 0
fecc0000-fecc03ff : IOAPIC 1
fee00000-fee00fff : Local APIC
fee00000-fee00fff : pnp 00:09
ff7c0000-ffffffff : reserved
fff80000-ffffffff : pnp 00:0e
I don't understand which memory addresses are being referred to here. Is it virtual memory?
Would it be possible to access these memory addresses from a user program to for example write into the serial port? Maybe using assembler?
Best Answer
Part of the design of the first IBM PC was to use some memory addresses for things other than actual memory (of the sort used by programs and data)
In the first IBM PC, you could have up to 640 KB of RAM but the chips could address up to 1024 KB of memory, however writing to memory addresses higher than 640 (and less than 1024) would actually be used to communicate not with RAM but with devices such as plug-in graphics adapters.
This concept is sometimes referred to as memory-mapped IO or memory mapped hardware devices.
IO ports are another type of addressable resource in the IBM PC architecture. In the early days you would physically configure such addresses on plug-in (ISA) cards by using "jumpers" to connect addressing pins on the board. You might also configure software to use matching IO addresses.
The white lettering on the left of the card describes which jumper positions give which IO Port addresses etc.
Nowadays, addressing details are negotiated and assigned dynamically by the cards and the host computer as the system starts up. We no longer have to configure them.
I believe so, assuming you are using an operating system that permits it (e.g. PC-DOS, a real-mode OS). In contrast, modern, protected-mode OSs will prevent such operations succeeding from a user program.