SD-card formatting: cluster size?
Kickaha
I write to ask for hints on SD-cards in HP49G.
I bought a 256MB one and formatted it via the HP49G+ (format command after
ON+D), so I guess the SD-card is now formatted with FAT-16. If I remember
well, FAT-16 can't have more than 65536 clusters, so doing 256MB/65536=4096
byte -> cluster size is 4KB.
Now the strange thing is that if I store something on the SD-card, the
amount of free memory showed via the filer says that there are only 2 KB
less! Also, I've tried to copy to the SD-card an object 1936 bytes long and
another variable 19 bytes long: I expected to have 4 KB less, but the filer
still shows only 2KB less!!!!! So what's going on? Is the card formatting
utility formatting my card in FAT-32 even if the screen clearly said me the
card was FAT-16 formatted??
ANy suggestion is appreciated
Regards,
Kickaha
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James M. Prange
Yes, for a 256MB card, a 4KB (8 sector) cluster size is appropriate.
With everything moved off the card to your hard drive, what size does
the filer say it is? With a 256MB card, I'd expect around
240000-245000 KB. If you're only getting about half of that, it would
tend to confirm that the cluster size is smaller than it ought to be.
Try reformatting the card from Windows, and if that gets you the right
cluster size, format it in the 49g+ again and see if it helps.
Worst case would be that maybe the formatting procedure refuses to
change the cluster size (I know it won't change the number of sectors
from what's already in the boot record), in which case you may have to
use a disk editor to tweak it.
--
Regards,
James
Kickaha
is the filer to uncorrectly show the amount of free disk space...
> Try reformatting the card from Windows, and if that gets you the right
> cluster size, format it in the 49g+ again and see if it helps.
...(SNIP)...
Any free-smart-small tool to get drive specifications (cluster size, ecc..)
you could suggest?!
Best regards,
Kickaha
James M. Prange
> "James M. Prange" wrote:
> I can confirm approx 248000 KB free with just formatted card: so it seems it
> is the filer to uncorrectly show the amount of free disk space...
Now that you mention it, I think I've seen other posts about the filer
showing only 128KB free on larger cards.
>>Try reformatting the card from Windows, and if that gets you the right
>>cluster size, format it in the 49g+ again and see if it helps.
>
> ....(SNIP)...
> Any free-smart-small tool to get drive specifications (cluster size, ecc..)
> you could suggest?!
Does your OS have MS ScanDisk available? If so, then try that; it
should give you the basic information.
--
Regards,
James
James M. Prange
> "James M. Prange" wrote:
> is the filer to uncorrectly show the amount of free disk space...
Now that you mention it, I think I've seen other posts about the filer
showing only 128KB free on larger cards.
>>Try reformatting the card from Windows, and if that gets you the right
>>cluster size, format it in the 49g+ again and see if it helps.
>
> ....(SNIP)...
> Any free-smart-small tool to get drive specifications (cluster size, ecc..)
> you could suggest?!
Does your OS have MS ScanDisk available? If so, then try that; it
Kickaha
> Kickaha wrote:
> I can confirm approx 248000 KB free with just formatted card: so it seems
it
> is the filer to uncorrectly show the amount of free disk space...
>
> Now that you mention it, I think I've seen other posts about the filer
> showing only 128KB free on larger cards.
uncorrectly the frre disk space, BUT indeed I WAS WRONG!
I've used the Analyze function from Defrag built-in in Windows2000 and it
says that the cluster size is 2 KB! What a great mistery! Microsoft clearly
saysy at
http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us
/Default.asp?url=/resources/documentation/windows/xp/all/reskit/en-us/prkc_f
il_lxty.asp that for a 256MB drive the cluster size will be 4KB with
FAT-16...
Is the calc formatting the SD-card in FAT32? Can the pre-formatting of the
SD-card influence further formats?
Any opinion welcome.
Kickaha
MM
If the 256 MB card is formatted with 2K clustersize, then this is a plain
bug in the device's OS.
MM
p.s.
I also had some "amazing" phenomenons with the SD card, depending on *where*
it was formatted...
I once stored a very large file (ca. 20 MB) on it and deleted it thereafter.
The HP 49G+ wasn't able to recover (or "see") the freed memory, even after
reformatting !!!
To mention here, reformatted on a card reader/writer.
The 20 MB were somehow "lost", until I reformatted *on the device*.
"Kickaha" <kickaha...@tiscali.it> schrieb im Newsbeitrag
news:cb7j79$ogo$1...@lacerta.tiscalinet.it...
James M. Prange
> "James M. Prange" wrote:
>
>>Kickaha wrote:
>>I can confirm approx 248000 KB free with just formatted card: so it seems
>
> it
>
>>is the filer to uncorrectly show the amount of free disk space...
>>
>>Now that you mention it, I think I've seen other posts about the filer
>>showing only 128KB free on larger cards.
>
> Do you mean 128000 KB?
Yes. I must've been in 48 series mode when I wrote that.
> Anyway what I mean is that maybe the Filer shows
> uncorrectly the frre disk space, BUT indeed I WAS WRONG!
>
> I've used the Analyze function from Defrag built-in in Windows2000 and it
> says that the cluster size is 2 KB! What a great mistery! Microsoft clearly
> saysy at
> http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us
> /Default.asp?url=/resources/documentation/windows/xp/all/reskit/en-us/prkc_f
> il_lxty.asp that for a 256MB drive the cluster size will be 4KB with
> FAT-16...
I guess someone at Microsoft is smart enough to figure out that with
FAT16, using 2K clusters would waste about half of a 256MB drive. But
sometimes their software gives strange results.
> Is the calc formatting the SD-card in FAT32?
I haven't heard of that, but who knows? I don't have an SD card big
enough to make FAT32 worthwhile. Actually, I not even sure that FAT32
is supported for drives smaller than 512MB.
Is your 49g+ running on ROM revision 1.23?
> Can the pre-formatting of the
> SD-card influence further formats?
Yes. For example, when I was fooling around, I trashed the card's boot
record, and experimentally found that neither the Windows 98SE format
nor the 49g+ format would change the number of sectors recorded in the
boot record. If I recall correctly, I temporarily changed my 128KB
card to a 16KB card. I ended up tweaking it with the disk editor. It
was fun though. I don't know whether a DOS format would've gotten it
straightened out.
Experimentally, I can tweak the cluster size either up or down in the
boot record, and the 49g+ is smart enough to change it back to
4-sector (2KB) clusters as appropriate for my 246016-sector card. I
sure hope it's smart enough to make 8-sector clusters for a 256MB
card.
> Any opinion welcome.
Do a web search for a disk/sector/hex/ASCII editor named WinHex and
download an evaluation copy. It's cripple ware in that the trial
version won't actually write to the drive, but it can give you a lot
of information.
To actually write to the card, I used an editor called Windisk. The
way it reports things is kind of screwy, and the PDF documentation
isn't in the ZIP file with the application. But it's free and it does
allow me to write to the card. It's available at:
http://dvalot.chez.tiscali.fr/
The 49g+ formats the card with some bogus information for drive
geometry. What matters for the card is the number of sectors specified
in the boot record, not what heads * cylinders * sectors per track
happens to work out to.
Of course, if you use a disk editor, be sure that you're editing the
card, not your hard drive.
--
Regards,
James
Matt M.
Nononononono ... boot record contains partition table, no actual FAT
data. All "format" utilities just format one partition, at whatever
size is reported in the boot record. To un-do what you did, you'd have
to use "fdisk". Except DOS fdisk doesn't do USB-attached disks (AFAIK).
So you'd have to use Linux fdisk =)
-MrM
James M. Prange
Perhaps you mean a "master boot record" (or "partition sector")?
But as far as I can tell, my SD card has no master boot record,
and thus no partition table. Some disk utilities do show me a
"partition table", but I'm a bit skeptical of a partition on the
card being hundreds of gigabytes or even terabytes in size. I
think what happens is that they look at sector 0 (the boot record)
and tell me what it would mean if it really were a master boot
record.
The boot record (or "boot sector" ) certainly does specify such
things as bytes per sector, sectors per cluster, number of FATs,
sectors per FAT, number of root directory entries, and total
sectors on the drive. If you have partitions it's at sector 0 of
each partition. But since my SD card doesn't have partitions, it's
at sector 0 of the card (or at least what the SD system presents
as being logically sector 0). It seems to be much like a floppy
disk, except a lot bigger than any floppy I've ever used.
If I null out the boot record and then tell the 49g+ to format the
card to 128MB, it writes in the boot record that it has 262144
sectors, which indeed works out to exactly 128MB (as long as we
define 1MB as 2^20 bytes). But if I try reading from or writing to
all of those sectors, I run into a bit of a problem. I chose
246016 sectors simply because that's the highest value that works
with Norton Disk Doctor without freezing up near the end of the
drive when I try a surface test. Once the card has a valid boot
record, the 49g+ uses the total sectors already recorded in the
card's boot record to determine the appropriate sectors per
cluster and sectors per FAT and doesn't prompt me for the card
size.
> To un-do what you did, you'd have
> to use "fdisk".
Oh, well, it works just fine for me without using FDISK on it.
> Except DOS fdisk doesn't do USB-attached disks (AFAIK).
That seems to be true.
> So you'd have to use Linux fdisk =)
Free FDISK seems to work pretty well.
What does your Linux fdisk tell you about the SD card?
But it might be interesting to put an MBR on the card. I wonder
how the 49g+ would respond to multiple partitions on the card. Or
what it would do with a card formatted as FAT32, for that matter.
--
Regards,
James
manjo
sector size 512 bytes
I was thinking:
since HP files are small often few bytes this will reduce the slack
-it works great and slack is only 2%
where on the other hand if you'd use 8k cluster you'd get more slack each
file no matter how small
would take at least 8k
(of course one must take care to choose proper sector/cluster size so that
FAT16 can cover
the whole available media)
i tried, but couldn't format my card to FAT32 (media too small),
but there is realy no use, because 512 bytes cluster size can cover my whole
16M card on
default FAT(16)
odd thing is:
some software reports FAT12 (not FAT16) being used on the card.
But i don't care (should i?)
-it all works as expected :-)
manjo