Hard disks with more than 137 GByte capacity

Hard disks with more than 137 GByte capacity

In view of the '137 GB problem', Maxtor launched the 'Big Drive' initiative without further ado. This problem is a limitation of the ATA standard for IDE hard disks, with which the maximum capacity of a hard disk can be 137 GB.

The addressing of the individual sectors is only possible with 28 bit long data, with which only 268,435,456 sectors can be addressed. With a sector size of 512 bytes, there is a limitation of 137.4 GB. Together with several other companies, including Microsoft, VIA, Compaq and Promise, Maxtor has now submitted a proposal to the ANSI standardization committee on how the limit of 137 GB can be exceeded and then an addressing of a maximum of 144 PetaByte (144,000,000 GB) becomes possible. The ANSI committee will integrate this proposal into the new ATA/ATAPI-6 standard. Among other things, the addresses are increased to 48 bits, which increases the maximum size of an IDE hard disk to 144 PBytes. Furthermore, the maximum amount of data that can be transmitted with a single command is increased. According to Maxtor's plans, the number of data that can be transferred per command will increase from 256 sectors to 65,536, i.e. from 128 KB to 32 MB per command.

The IDE interface itself has hardware moderately no changes to be made, but operating system and BIOS manufacturers are now in demand. The system must now make the new addressing possible with 44bit instead of only 28bit and the BIOS must recognize a new type of hard disk with full size and be able to pass the 48bit instructions to the HDD. The first models of HDDs with more than 137 GByte capacity should be available this year. One generally reckons with up to 160 GB by the end of 2001.