The ATA/IDE Interface - Upgrading and Repairing PCs - page 420

Terabytes (TB) 144,115
Tebibytes (TiB) 131,072
Petabytes (PB) 144.12
Pebibytes (PiB) 128.00
As you can see, the 48-bit LBA in ATA-6 allows a capacity of just over 144PB (petabytes =
quadrillion bytes)!
Because the EDD BIOS functions use a 64-bit LBA number, they have a much larger limit:
Click here to view code image
Max. Values
---------------------------------------------
Total Sectors 18,446,744,073,709,551,616
---------------------------------------------
Total Bytes 9,444,732,965,739,290,427,392
Megabytes (MB) 9,444,732,965,739,290
Mebibytes (MiB) 9,007,199,254,740,992
Gigabytes (GB) 9,444,732,965,739
Gibibytes (GiB) 8,796,093,022,208
Terabytes (TB) 9,444,732,966
Tebibytes (TiB) 8,589,934,592
Petabytes (PB) 9,444,733
Pebibytes (PiB) 8,388,608
Exabytes (EB) 9,445
Exbibytes (EiB) 8,192
Zettabytes (ZB) 9.44
Zebibytes (ZiB) 8.00
Although the BIOS services use 64-bit LBA (allowing up to 2 64 sectors) for even greater capacity, the
144 petabyte ATA-6 limitation is the lowest common denominator that would apply. Still, that should
hold us for some time to come.
Because hard disk drives have been doubling in capacity every 1.5 to 2 years (a corollary of Moore's
Law), I estimate that it will take us until sometime between the years 2031 and 2041 before we reach
the 144PB barrier (assuming hard disk technology hasn't been completely replaced by then).
Similarly, I estimate that the 9.44ZB EDD BIOS barrier won't be reached until between the years
2055 and 2073! Phoenix originally claimed that the EDD specification would hold us until 2020, but
it seems they were being quite conservative.
The 137GB barrier proved a bit more complicated than previous barriers because, in addition to
BIOS issues, operating system issues also had to be considered.
Internal ATA drives larger than 137GB require 48-bit LBA (logical block address) support. This
support absolutely needs to be provided in the OS, but it can also be provided in the BIOS. It is best
if both the OS and BIOS provide this support, but it can be made to work if only the OS has the
support.
Having 48-bit LBA support in the OS requires one of the following:
• Windows XP with Service Pack 1 (SP1) or later.
• Windows 2000 with Service Pack 4 (SP4) or later.
• Windows 98/98SE/Me or NT 4.0 with the Intel Application Accelerator (IAA) loaded and a
motherboard with an IAA-supported chipset. See http://downloadcenter.intel.com and search
for IAA.
Having 48-bit LBA support in the BIOS requires either of the following: