Hard disk Working mode

The motherboard now supports three hard disk working modes: NORMAL, LBA, and large mode.

Normal Normal mode is the earliest IDE way. In this manner, the BIOS and IDE controllers do not convert any parameters to the hard drive when it is accessed. The maximum number of cylinders supported by this mode is 1024, the maximum number of heads is 16, the maximum number of sectors is 63, and the number of bytes per sector is 512. Therefore, the maximum hard drive capacity is supported: 512X63X16X1024=528MB. In this mode, even though the actual physical capacity of the hard disk is larger, the available hard disk space can only be 528MB.

LBA (Logical block addressing) logical chunk addressing mode. This mode manages the hard disk space to break through the 528KB bottleneck, up to 8.4GB. In LBA mode, the set of parameters such as cylinder, head, sector, etc. are not physical parameters of the actual hard disk. When accessing the hard disk, the IDE controller converts the logical addresses determined by parameters such as cylinder, head, sector, and so on to the physical address of the actual hard disk. In LBA mode, the maximum number of heads that can be set is 255, and the remaining parameters are the same as normal mode. This allows you to calculate the capacity of the accessible hard disk: 512X63X255X1024=8.4GB.

Large large hard drive mode. This pattern can be used when the cylinder of the hard disk exceeds 1024 and is not LBA supported. The large mode takes a method of dividing the number of cylinders by 2, multiplying the number of heads by 2, and the total volume of the results is unchanged. For example, in normal mode, the number of cylinders is 1220, the head number is 16, the number of cylinders entering large mode is 610, and the head number is 32. This will work correctly in DOS if the cylinder number is less than 1024. At present, only LBA is practically meaningful.