| ??? 01/11/08 09:23 Read: times |
#149302 - and more... Responding to: ???'s previous message |
On Intel 8086 and 80186 IOports was only in IOspace(64kB).Processor has dedicated strobes IO_Write,IO_Read. IN and OUT instructions use these stobes.
From 80386(or 80286?) IOports can be memory mapped - i think only in protected mode, but i'm not sure. Mapped ports can be accessed trough memory access instructions. On my PC (Athlon 2+GHz) onboard PCIExpress SATA contoller occupies 09f0,0BF0 and other such IO addresses (seen from DeviceManager/System/Control_panel on WinXP). Each IO add-on card has address decoder, which recognises address bus and IO strobes. Hystorically IBM introduces PC in time, when chips are expensive. So decoder was limited to first 10..11 address bits and not to whole 16 bits. regards stefan |
| Topic | Author | Date |
| PC Ports - Just curious | 01/01/70 00:00 | |
| x86 has a separate IO space from memory space... | 01/01/70 00:00 | |
| Misunderstanding? | 01/01/70 00:00 | |
| 10bits | 01/01/70 00:00 | |
| 16 bits | 01/01/70 00:00 | |
| and more... | 01/01/70 00:00 | |
| Memory mapped? | 01/01/70 00:00 | |
| yes | 01/01/70 00:00 | |
| cache... | 01/01/70 00:00 | |
| IP Ports | 01/01/70 00:00 | |
| Yes thats what I was looking for... | 01/01/70 00:00 | |
Nothing specifically to do with PCs, then! | 01/01/70 00:00 |