Welcome guest, is this your first visit? Click the "Create Account" button now to join.
Results 1 to 3 of 3
  1. #1
    Garmin/GPS Systems GMod.

    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Oz.
    Posts
    7,391
    Rep Power
    1434

    Default Explanation of Actual Drive Space Availibility [in Laymen's Terms]

    First try to get your head around this: There are two uses of the terms kilobyte [kB], megabyte [MB], gigabyte [GB], terabyte [TB] etc.. The original I.T. 'binary' use which uses a factor of 1024 and the more recent 'decimal' use which uses a factor of 1000. See what's going to be happening there? Not a big difference with a kilobyte, only 24 bytes between the binary form [1024 bytes] and decimal form [1000 bytes]. But when we get to looking at a terabyte we're talking of 1,099,511,627,776 and 1,000,000,000,000 respectively so it's a huge difference of 99,511,627,776 bytes. That's almost 100 GB decimal or between 92 and 93 GiB [GB binary]. So the so called 2 TB drive you just bought is only a little over 1.8 TB according to your Windows PC. But both still mean ~2,000,000,000,000 [2 trillion] bytes though. Further explanation below about Microsoft's and the drive manufacturers' attitudes to use of binary and decimal terms and their conflation.

    There's a file size limit which still applies to some Garmin automotive devices such as nuvi 3xx, 6xx and all StreetPilot models and earlier Garmin devices and the limit is actually 1 byte under 2 GiB [gibibytes] i.e. 2,147,483,647 bytes which is about 2.15 GB [gigabytes]. In binary terms that's ~1.99999999906868 GiB [gibibytes]. It's the exact same limit which applies to any files under FAT16 [loosely referred to as just FAT by Windows OS's].

    Other earlier devices such as US/EU nuvi 2x0(W), 2x5(W), 465, 7xx once limited as above for map files on a media card can with latest firmware [for some many years now] use map *.img files up to the 4GiB minus 1 byte file size limit imposed by FAT32, i.e. 4,294,967,295 bytes or a little under 4.3 GB. Garmin presently does not produce single map images of 4 GiB or above in deference to the FAT32 limit. That conceivably may change with release of devices capable of using newer file formats such as exFAT which supports extraordinarily large file sizes and as Garmin drops support for older devices.

    It's also a popular 'folk-law' that all devices with the so-called '2 GB limit' are limited to using only [again 'so-called'] 2 GB [gigabytes] media cards, but some are and StreetPilot c3x0 is an example. No longer produced for the retail market, 2 GB cards were supplied factory formatted in FAT[16] and usually have something over 1.8 GiB [gibibytes] actually available hence the urban myth arose that ALL those devices can only use a '1.8 GB map img file'. Nominally the 2 GB cards would have theoretical storage of 2,000,000,000 bytes available or ~1.86 GiB but some is used for hardcoded info already so it's less, more like between 1.82 and 1.84 GiB depending on manufacturer. All older Garmin devices I've tested which actually can use large FAT32 formatted cards, despite some still having the '2 GB' file size limit and having their internal flash space formatted in FAT[16] or even as 'region-only' without a visible file system internally, work fine provided the IMG FILE is under 2 GiB. The workaround for the others if you can't find a 2 GB card is to create a smaller ~2 GB partition on a larger card and format it FAT16 then leave the rest unallocated, it's no big deal as you can't put a bigger .img file on the card and are limited to one gmapsupp.img in Garmin folder with such devices anyway.

    Anecdotal observation is CF cards do have a little more available space than SD and microSD cards of same nominal size. Also, StreetPilot 26x0 can use up to 32 GB FAT32 CF card provided the 2GiB file size limit is respected as an example.

    Microsoft, unfortunately but no doubt unintentionally though stubbornly, perpetuates the confusion by clinging to the original binary 'notation type' of 1024 for 'kilo' whereas the hard and flash drive manufacturers have long since hijacked the term to use as a decimal factor of 1000. Hence 1 kB [kilobyte] = 1000 bytes decimal, or 1024 bytes if it's Microsoft's binary 'kilobyte' [really kibibyte/KiB]. The difference increases exponentially the larger the drive as explained in red above, check the properties in Windows of a large HDD to see the total available space. That will show as something quite less and an apparent 'loss' of space compared to if they were 'binary' endowed by the drive manufacturers as for example 2 TiB and 3 TiB would have 2,199,023,255,552 and 3,298,534,883,328 bytes respectively and that's a lot of bytes down the gurgler. In fact 298,534,883,328 bytes is over 278 GiB or ~298.5 GB. Imagine how wide the difference will be when we start using yottabytes/yobibytes for drives at consumer level. Multiply each notation type of 1000 or 1024 by itself 8 times to see because they're to the power of 8. We started off losing only something over 2.3% with kB to KiB but approaching 5% with MB to MiB and almost 7% with GB to GiB. This is how it goes roughly:

    • 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

    and so on ......

    The downward progression in space 'lost' is very clear when put like that and we see that our now common TB drives are 'missing' over 9% of usable space and as drives get bigger so will the proportional 'apparently lost' storage space continue.

    Note that Garmin's MapInstall program in Windows toes the binary 'party line' with Microsoft and will measure the map tiles size in binary 'GB'. Therefore although it will show the cumulative size as GB you do need to limit the map img files compiled from it accordingly to no more than ~1.99 or ~3.99 'GB' as applicable to be sure you're keeping them under the 2 or 4 GiB limits.

    It's only hard to understand because of the confusion/conflation of terms compounded by M$'s stubbornness, but it's much better to make the effort to understand this than simply carry on believing and perpetuating the old wives' tales. It's better to use gibibyte [GiB] not gigabyte [GB] when we mean the binary form and avoid use of anything other than the standard EN abbreviation forms. In this EN-only forum please avoid the use of the Continental 'Go'. Similarly avoid the nonsense 'gb' and don't incorrectly use 'Gb' [that's gigabit] when you mean 'GB' the 'decimal gigabyte'. Otherwise the confusion will just continue to swirl.

    Some references:
    Code:
    Please Login or Register to see the links
    Full credit to our much revered Ballebar for helping me to understand this many years ago. [Come back BB, we miss you so bad!]
    'Thanking Posts' are banned. To thank someone, and/or to see hidden links and content, use the [Only registered and activated users can see links. ] button below left of the helpful post then refresh your browser [F5 key]. 'Thanking Posts' are banned.
    Please don't spam. Posts serving no purpose other than to thank or to ask about hidden links are trashed or deleted, it's GPSPower's policy. Please don't spam.
    [Only registered and activated users can see links. ] should make their first post as a new Intro Thread in [Only registered and activated users can see links. ].

  2.    Advertissements


  3. #2
    Senior Member Strephon Alkhalikoi's Avatar
    Join Date
    Feb 2011
    Location
    Massachusetts, United States
    Posts
    264
    Rep Power
    164

    Default

    The confusion is the fault of the storage companies, not Microsoft. Microsoft used SI units for years prior to the introduction of IEC binary prefixes . Storage companies should be using SI units, not IEC.
    [Only registered and activated users can see links. ]
    [Only registered and activated users can see links. ]
    [Only registered and activated users can see links. ]

    "Anyone who is capable of getting themselves made President should on no account be allowed to do the job."
    --Douglas Adams

  4. #3
    Garmin/GPS Systems GMod.

    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Oz.
    Posts
    7,391
    Rep Power
    1434

    Default

    I agree, but it's like trying to hold back the tide with your hands. Like i said "........the hard and flash drive manufacturers have long since hijacked the term to use as a decimal factor of 1000" and i wasn't really saying it's MS's fault as such, i do quite agree with them in fact on a pedantic and intellectual basis. But we need keep in mind that the majority of PC users are mere mortals these days, not coders or IT experts like most were back in the DOS days. We may as well say 'Australia and New Zealand should go back to Pounds, Shillings and Pence instead of Dollars and Cents as currency' as say 'the drive manufacturers should revert to SI units'. It will never happen [either of them ] and Mac OS X since V10.6 and modern Linux use the decimal notation type so that only makes it harder for the average Joe with MicroSoft staying with the binary forms. Plenty of ppl have a mix of OS types say a PC or Mac for home use and an iPad/Mac lappy or Andoid tablet or Win laptop/tablet etc for out and about. If MS don't want to change the notation type from 1024 to 1000 [and i don't think they should to be frank] they could at least use the prefixes of kibi, mebi, gibi and tebi, with the symbols Ki, Mi, Gi and Ti respectively to help ease the confusion. I know MS has been around much longer than the organizations that tried to sort this mess out about 20 years ago. It took another 3 years until 1999 when the standards were adopted and in the last 17 years i doubt more than 10% of PC users would've come to understand wotthehell is going on. If MS sticks to their determination to be 'right' [they are] it will only continue to add to the confusion and ppl will endlessly be confounded by all this. If they'd at least use GiB instead of GB it would help.

    Anyway, my main reason for posting the tut was not to start a brushfire on use of prefixes although i well-and-truely put my big flat foot in that camp. My primary aim was to have a 'point of reference' to give ppl who post incorrect and/or confusing information in Garmin threads. If we don't get the terms right the only way to know exactly what ppl are inferring is to talk only in bytes and for large files that's billions of the little b's ....

    So don't even get me started on clock speeds, data transfer and RAM size and if you mention bits under different types of OSs, 32 bit or 64 bit for instance, i may just pop an aneurism ......
    'Thanking Posts' are banned. To thank someone, and/or to see hidden links and content, use the [Only registered and activated users can see links. ] button below left of the helpful post then refresh your browser [F5 key]. 'Thanking Posts' are banned.
    Please don't spam. Posts serving no purpose other than to thank or to ask about hidden links are trashed or deleted, it's GPSPower's policy. Please don't spam.
    [Only registered and activated users can see links. ] should make their first post as a new Intro Thread in [Only registered and activated users can see links. ].

 

 

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
This website uses cookies
We use cookies to store session information to facilitate remembering your login information, to allow you to save website preferences, to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.