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Tyler
No, just remember generalized "keywords" that will help you re-find stuff later. Or use bookmarks. It always works for me with the few things I've managed to learn.
I suggest you go with FAT16 or FAT32 because of how 12 always leaves you with that awkward nibble to deal with. |
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26 Apr 2010, 22:14 |
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edfed
i recommend you to read a lot of old threads in this sub forum.
you will see many interresting datas in earlier pages. and yuo xwill find many implementations for FAT12, ready to use, many others for FAT32 or 16, and other interresting stuff  |
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27 Apr 2010, 00:52 |
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roboman
http://www.brokenthorn.com/
http://www.osdcom.info/component/option,com_frontpage/Itemid,1/ and lots of stuff here Dex has a simple and a less simple OS MikeOS is also a great example Lots of others, those just come to mind quickly |
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27 Apr 2010, 05:12 |
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adroit
Thanks!
- I will start with Fat12, then graduate slowly as i learn more about file systems. - I've found a few good threads as i browsed. - osdcom.info and brokenthorn.com are two of the best sites I've seen. |
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27 Apr 2010, 12:52 |
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revolution
FAT12 would actually be harder to code than FAT16 for FAT32.
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27 Apr 2010, 12:55 |
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adroit
Really? So should I code FAT16 instead of FAT12?
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01 May 2010, 15:22 |
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edfed
some M$ document about fat say that the 3 fat versions are needed.
fat12 for little drives. fat16 for middle drives. fat32 for large drives. |
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01 May 2010, 15:50 |
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Dex4u
revolution wrote: FAT12 would actually be harder to code than FAT16 for FAT32. 
Also beginners think, coders that have been coding for some time memorizes everything. But we just look it up, the only difference is we know where to look it up.  |
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01 May 2010, 18:02 |
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adroit
I think I will code a FAT12 just to get more experience and take FAT16 into consideration.
Dex4u I don't have to take everything to memory except the basics, like knowing how to code. |
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03 May 2010, 20:27 |
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Tyler
MeshNix wrote:
I even have to look that up every once in a while.
But you may want to consider the fact that when you start to read the FAT of the FAT12 fs, you'll have to deal with the leftover nibble. |
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04 May 2010, 00:37 |
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adroit
What exactly is the leftover nibble? The nibble comes from where exactly?
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06 May 2010, 04:40 |
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baldr
MeshNix,
Tyler means that standard 512-byte sector contains 341⅓ FAT12 entries. |
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06 May 2010, 05:39 |
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revolution
MeshNix wrote: What exactly is the leftover nibble? The nibble comes from where exactly? |
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06 May 2010, 05:43 |
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bitshifter
The overlap is where people get lost with FAT12...
Code: 0000000000001111 1111111100000000 0000111111111111 So this means that only 12 bits per word are used. The extra 4 bits belong to the next group and so on... |
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06 May 2010, 12:05 |
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smiddy
MeshNix wrote: What exactly is the leftover nibble? The nibble comes from where exactly? |
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06 May 2010, 12:37 |
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edfed
franckly, fat12 is one of the worse designs never used to be a standard.
it is limited to only drives with less than 4192 sectors.. means that it is a pure limitation. does OSes supports other file systems for floppies? like FAT16 for example... it is like the 20bits address bus limitation in early 8086... does franckly the deisgners thinked about the possibility of 4GB of ram? etc... or the LBA28... or the 24bpp, or else.... Last edited by edfed on 06 May 2010, 23:24; edited 1 time in total |
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06 May 2010, 18:35 |
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Tyler
baldr wrote:
Actually, I never even thought of that  , although that too would be annoying. I was just talking about how that nibble would make reading the FAT a pain. Poor choice of words I guess. I think bitshiter is showing an example of what I meant.
Yet another reason not to use FAT12. |
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06 May 2010, 21:45 |
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baldr
edfed wrote: franckly, fat12 is one of the worse designs never used to be a standard. Number of clusters on FAT12 volume indeed is limited (4084 max), with maximum allowed cluster size of 32 KiB that's 127.625 MiB. FAT12 looks like good compromise for late-'70-born floppy disk file system: simple and compact, yet flexible (pre-2.0 DOSes didn't support directories, for example). IBM 5150 PC was 8088-based with 16 KiB RAM minimum — not a much room and power. ----8<---- Tyler wrote: Yet another reason not to use FAT12. Code: ;;; si = cluster number mov bx, si shr bx, 1 mov ax, FAT12[bx+si] jnc @f shr ax, 4 @@: and ah, 0x0f ;;; ax = next cluster number or free/bad/EOF marker |
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06 May 2010, 23:40 |
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adroit
I am totally lost!
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09 May 2010, 21:58 |
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