The program control code began to be built into the BIOS carried by the motherboard, thus no longer relying on the ROM chip carried by the interface control card.
The system began to support the newly added high IRQ interrupt number, canceled the occupation of DMA channel and changed the I/O address used by the hard disk interface.
The hard disk interface in AT specification is as follows: IRQ 14 is used.
Use the I/O interface address 1F0- 1F8.
No longer occupy DMA channel.
Use the program code built in the motherboard BIOS to control the hard disk interface.
Use an operating system above DOS2.0.
The hardware setting information of AT-compatible computer is saved on a CMOS chip, and the recorded content is maintained by a small battery.
Therefore, even if the power of the chassis is turned off, all settings will still be saved.
This technology makes PC users no longer have to be bothered by a large number of jumpers and toggle switches (in early computers, the system resources occupied by each device were allocated by users manually changing jumpers or toggle switches), and the contents recorded in CMOS can be easily changed by running a simple program, which is also a great progress in improving computer usability.
The original AT specification defined 14 hard disk, with the capacity ranging from 10MB to 1 12MB * *. When using those substandard hard disks, it is still necessary to carry ROM chips or load special device drivers on the interface card when the system is started.
Before DOS4.0, the operating system did not support partitions above 32MB. Even if you use a hard disk with a capacity of 100MB or more, you have to cut it into units before you can use it. This is because of the traditional limitation that "the total number of sectors in the system cannot exceed 65,438+06 bits (65,536)".
If you want to use partitions larger than 32MB, you must use special partitioning tools, such as Ontrack's sDiskManager (even today, the new version of DiskManager is still welcomed by users, which is a magic weapon to solve the problem that the old motherboard does not support large-capacity hard disks). At that time, many hard disk manufacturers bundled DiskManager with their own products.
Unfortunately, there are compatibility problems between DiskManager and many other disk tools, because under most tool software, the partitions divided by DiskManager will be identified as non-DOS (non-DOS) partitions.
So many users are forced to use large-capacity hard disks by dividing a number of small partitions below 32MB, but this method also has limitATions, because the version before DOS3.3 did not support the concept of extended partitions at all ... Now users certainly don't have to pay attention to these restrictions, because the types of hard disks supported by AT compatible machines have increased to more than 40, and most BIOS will provide an option for users to freely set various hard disk parameters.
As long as you open the hard disk properties in the WINDOWS operating system, you can see the words "genericdediskTYPE46/47/47 47/47" (whether to display 46 or 47 is related to the system settings; when the hard disk type is set to USER in the BIOS, it is displayed as type 46 and when it is set to AUTO, it is displayed in the system properties), which is the "inherent hard disk type" to which your hard disk belongs.
Of course, in the WINDOWS environment, users don't need to care about what type of hard disk is set, because with the development and progress of the operating system itself, WINDOWS itself can read and write the hard disk correctly without reading this parameter.
However, some clauses in the original AT specification are still the shackles of today's PC. For example, a PC can only connect two hard disks at most, and the BIOS/ operating system can only recognize restrictions such as 1024 cylinder, 16 head and 63 sectors/tracks. Of course, these restrictions have been overcome now.
People have adopted many different methods to convert those "substandard" physical parameters into logical parameters that the system can support.