**2^10 vs. 10^3**

Historically most people defines 1 kilobyte as 2^10=1024 bytes, 1 megabyte as 1024 kilobytes, 1 gigabyte as 1024 megabytes and so on. That's the definition that was used in the beginning of calculating bits and bytes in computers and PCs.

Storage manufacturers have hijacked the term and by political and technical lobbying got the SI definition of decimal counting for kb, MB, GB, TB etc. to be commercially accepted. They claim that k stands for 10^3=1000, M for 10^6=1000000, G for 10^9=1000000000 and that it allows them to use the decimal definition of prefixes for bytes. That even despite the de facto standard for computer science had been binary 1024 calculated prefixes for decades.

When we where using kB and MB it didn't matter so much if it was decimal or binary definition behind the symbols. But we loose approx. 2.34% for each step in the k -> M -> G -> T -> P ...

1 kB is ~97.66% of 1 KiB

1 MB is ~95.37% of 1 MiB

1 GB is ~93.13% of 1 GiB

1 TB is ~90.95% of 1 TiB

1 PB is ~88.82% of 1 PiB

...

...

So with TB and PB we have lost close to 10% or more from what many of us actually expected from binary calculated units.

**Gigabytes vs. gibibytes class action suit nears end**

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Microsoft still uses the term gigabyte (GB) as calculating 1024 MB or 1024*1024 kB or 1024*1024*1024 bytes. I'm also using 1 GB as 1024 MB in normal everyday life but tries to be as accurate as possible here in the Noeman forum. So here at Noeman I'm trying to use KiB, MiB, GiB when appropriate. Most file host forums also shows MB but uses binary calculation such as it should be displayed as MiB instead.

We could even complicate it further by using the original definition of a byte - one **data word** used for CPU calculation or data storage. That means 1 byte = 4 bits in a 4-bit CPU world, 1 byte = 8 bits in a 8-bit CPU environment and so on. In my Windows 7 64-bit OS that would mean 1 byte = 64 bits.

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**2^32**

If you have a FAT32 file system it means the address space is 32-bits. Calculating from address 0 (zero) and up to 2^32-1. The -1 comes from that you start with address 0. That's the maximum unsigned 32-bit integer that could be used in linear addressing. This is equal to 4 GiB - 1.

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**Some (un)usefull historical data**

In the old DOS days with 16-bit application there was a lot of tools like DOS Phar Lap Extender to break the OS limit of 16-bit addressing. By using such extenders they could write 32-bit applications to run in a 16-bit OS.

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**About the total numbers of map families (MapIDs) that can be used at the same time in a Garmin unit.**

I haven't tried to measure this by science and taking the time to test my Garmin units. If I load my 32 GB Samsung Class 10 microSDHC card with 4 City Navigator NT, 7 TOPO maps and 6 BC g2 the result is that some maps is not seen by the unit.

Perhaps Mapperoni would be kind and share his more exhaustive evaluations of that subject. I think Mapperoni tested the capacity of a GPSmap 62 unit with TOPO Norway Adventure. There's a total of 20 maps in that series and all have a different MapID.

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