Thinkpads Forum

I got a new T61, actually ordered for 160GB 5400 RPM with vista home premium, the capacity shows total capacity as 142GB will it be that much less?

File system is NTFS

any idea why the capacity is less?

Service partition on your HDD takes around 4-6GB, also HDD's capacity is always less and differs from the advertised size by a few GB's. This is due to the different measurements (Base 2) used by HDD manufactures (1000 MB per GB). Your computer uses the correct measurement (1024 MB per GB). So for e.g. if you HDD space was advertised as 100GB then actual size will be around 94GB.

For more info. you might consider reading the following article:

When a Byte is not a Byte.

Also take a look at the following thread:

why my available HDD under Vista is decreasing.

ryengineer wrote:Your computer uses the correct measurement (1024 MB per GB). So for e.g. if you HDD space was advertised as 100GB then actual size will be around 94GB.

This is mostly correct, except the SI prefixes are mostly supposed to be base 10 (e.g 1000) and not base 2 (1024). 1024 MiB is 1 GiB. It's a common misconception propegated ever since the early days of computer science that 1024 bytes of main memory should be called a kilobyte of main memory since 1024 is close enough to 1000. It makes sense to count main memory in base 2 (KiB, MiB, GiB, TiB, etc), but it makes little sense to count linear storage in base 2. Base 10 is perfectly adequate to reference linear storage, like hard drive spec. The drive manufactures do just that. People often use the SI prefixes to mean both 1000 bytes or 1024 bytes, depending on the context. Strictly both values are correct (historical reasons), but that convention does lead to confusion.

http://en.wikipedia.org/wiki/Binary_prefix

http://en.wikipedia.org/wiki/Mebibyte

http://en.wikipedia.org/wiki/Gibibyte

http://en.wikipedia.org/wiki/Kibibyte

http://en.wikipedia.org/wiki/Kilobyte

I'll include the above Wikipedia articles, with the understanding that Wikipedia isn't actually the best academic source, or even all that authoritative. But it does illustrate the difference.

In short, ryengineer is correct that the conversion of the represented space from base 10 to base 2 results in a 7% apparent reduction (100GB = (approx) 93GiB), there are some losses due to the act of disk formatting (not that much), and there are is loss of several GB -- which depends on the OS -- due to the recovery partition.

Aroc wrote:It makes sense to count main memory in base 2 (KiB, MiB, GiB, TiB, etc), but it makes little sense to count linear storage in base 2

Since its the same stuff that is being held in both "memory" and "storage", it makes no sense at all to use different number bases for referring to the capacity of either!

Cheers,

Bill B.

bill bolton wrote:Since its the same stuff that is being held in both "memory" and "storage", it makes no sense at all to use different number bases for referring to the capacity of either!

It's not exactly the same stuff though being held in both places. What's read, held, and executed in main memory is a bit different that what is held in storage. This is taught in introductory computer science courses. I do agree that is makes little sense to use two schemes. and it makes just as little sense to use the wrong base prefixes for a different counting base. It probably would have made more sense to lets humans see everything in base 10 but let the computer use main memory (internally) in base 2. Then things would have been more consisent and far less confusing for the humans who need to use and make sense of this stuff.