SD versus SDHC Cards?
Discussion
I know there are two types and both can come in 4GB flavour. It seems that your unit (whatever it is) must support the newer type (SDHC) to work with an SDHC card - does anyone have any experience of using an SDHC card in their products where it was delivered with the older SD card type?
SDHC uses a completely different addressing strategy to allow more than 2 GB to be easily addressed. Yes there are 'SD' cards in 2 GB and 4 GB capacities but the vast majority of the 4 GB ones don't conform properly to either the SD or the SDHC standard.
SDHC readers as a *standard* will read all *standard* SD cards as they've got specific backward compatibility designed in.
The problem is with the cards that are neither fish nor fowl - the 'sort-of' SD 2 and 4 GB cards. I would strongly advise just getting a proper SDHC if you're going to that capacity and upgrading your card reader.
As to SDHC in 'old' SD readers... SDHC is meant to be incompatible but it's the same physical interface so the support is purely a matter of firmware in the reader. For example, I've got a 5-way card reader that takes SD, compact flash, Sony memory sticks, those crappy fragile cards that early digital cameras used, etc. This *did* read a 2 GB SDHC card (proper Sandisk branded ultra jobbie) but only presented the card as a 1 GB device - theoretically it shouldn't have worked at all (and a 1 GB limit is right proper oddball, since you'd expect any hard limit to be along byte boundaries, which for 32 bit gives 2 GB).
I bought a proper SDHC reader (Sandisk Imagemate 5 in 1 reader) which happily deals with the biggest SDHC cards I own (4 GB) as well as old SD cards, along with a 'in-between-standards' 2 GB card I have (which doesn't play nice with my camera).
Rambling a bit but I'd go SDHC and upgrade your kit if possible to suit. SDHC comes in handily big sizes (the risk of data theft with these things is huge) but more importantly, the standard specifies guaranteed minimum transfer speeds. You can be sure that a Class 6 card will write 6 MB/sec to a fresh card.
SDHC readers as a *standard* will read all *standard* SD cards as they've got specific backward compatibility designed in.
The problem is with the cards that are neither fish nor fowl - the 'sort-of' SD 2 and 4 GB cards. I would strongly advise just getting a proper SDHC if you're going to that capacity and upgrading your card reader.
As to SDHC in 'old' SD readers... SDHC is meant to be incompatible but it's the same physical interface so the support is purely a matter of firmware in the reader. For example, I've got a 5-way card reader that takes SD, compact flash, Sony memory sticks, those crappy fragile cards that early digital cameras used, etc. This *did* read a 2 GB SDHC card (proper Sandisk branded ultra jobbie) but only presented the card as a 1 GB device - theoretically it shouldn't have worked at all (and a 1 GB limit is right proper oddball, since you'd expect any hard limit to be along byte boundaries, which for 32 bit gives 2 GB).
I bought a proper SDHC reader (Sandisk Imagemate 5 in 1 reader) which happily deals with the biggest SDHC cards I own (4 GB) as well as old SD cards, along with a 'in-between-standards' 2 GB card I have (which doesn't play nice with my camera).
Rambling a bit but I'd go SDHC and upgrade your kit if possible to suit. SDHC comes in handily big sizes (the risk of data theft with these things is huge) but more importantly, the standard specifies guaranteed minimum transfer speeds. You can be sure that a Class 6 card will write 6 MB/sec to a fresh card.
AMG Merc said:
Thanks but can't change my reader as it's part of the SatNav so I'd better go for a standard SD 4GB!
Does your satnav state any specific cards as being compatible though?The difference between SD and SDHC is FAT16 support and FAT32 support. It is just a firmware update for most devices to add this.
I'm intrigued as to why a card reader would have trouble though - the majority of the "intelligence" on them is actually on the PC that its connected to? Unless you've got a relatively nasty card reader?
clonmult said:
AMG Merc said:
Thanks but can't change my reader as it's part of the SatNav so I'd better go for a standard SD 4GB!
Does your satnav state any specific cards as being compatible though?The difference between SD and SDHC is FAT16 support and FAT32 support. It is just a firmware update for most devices to add this.
I'm intrigued as to why a card reader would have trouble though - the majority of the "intelligence" on them is actually on the PC that its connected to? Unless you've got a relatively nasty card reader?
AMG Merc said:
clonmult said:
AMG Merc said:
Thanks but can't change my reader as it's part of the SatNav so I'd better go for a standard SD 4GB!
Does your satnav state any specific cards as being compatible though?The difference between SD and SDHC is FAT16 support and FAT32 support. It is just a firmware update for most devices to add this.
I'm intrigued as to why a card reader would have trouble though - the majority of the "intelligence" on them is actually on the PC that its connected to? Unless you've got a relatively nasty card reader?
Admiteddly, the majority of the 4gig SD cards advertised on E-Bay aren't reputable, I wish my ex step daughter had asked me before she went and ordered one for her Nokia. She phoned me asking "How do I get this to work on my phone?" The answer was "You can't, you were conned".
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