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Thread: Larger-Smaller memory cards...

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    rpcrowe's Avatar
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    Larger-Smaller memory cards...

    Should there be any difference in read/write speeds of the same speed and UDMA type cards (I am specifically asking about CF cards) that are of different sizes. I don't have any cards of the same brand and speed and of different sizes to test this.

    In other words does CF card memory work like RAM, with the larger amount of memory being faster.

    So as an example, would a 16 gig, Lexar, 400x, UDMA, CF card read/write faster than a 4 gig, Lexar, 400x UDMA, CF card; considering that I would be shooting with the same camera and downloading with the same setup!

    I do know that UDMA cards will write faster and will transfer data faster (when using a UDMA capable reader) than non-UDMA cards - if the camera can take advantage of UDMA capability.

    The UDMA cards also download considerably faster if I use a UDMA capable card reader than when I use a non-UDMA reader.

    Even when shooting a camera (such as my backup 40D) which doesn't take advantage of UDMA capability, downloading the cards to a computer with a UDMA capable reader is considerably faster than downloading with a non-UDMA capable reader.

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    PhotomanJohn's Avatar
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    Re: Larger-Smaller memory cards...

    Richard - I believe the read/write speeds should be the same as the rating on the cards suggest. Your comment about being like RAM and the more the faster I believe references that computers process things generally faster if they have more memory. This is a different thing. The speed gain is because the program can keep more of what it is working on in memory so it doesn't have to access the disk drive as much which speeds the processing up. The actual speed of the RAM does not change.

    Did I understand your question and did this help?

    John

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    rpcrowe's Avatar
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    Re: Larger-Smaller memory cards...

    Thanks John. I suspected as much. This was one of those "interesting" but useless questions which keep popping into my brain!

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    Moderator Dave Humphries's Avatar
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    Re: Larger-Smaller memory cards...

    Not relevant to Richard's question, but given the all encompassing thread title, I'll just say ...

    With SDHC cards in a bridge camera, I have found that supposedly faster large cards can be slower writing to than smaller, slower cards.

    From (my) memory; 32GB C10 was slower than 4GB/8GB C2/C6 cards in a Nikon P510.
    Can only assume there's some bottle neck in address decoding that causes this.

    Same cards in DSLR (Nikon D5000) behave more as one would expect

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    rpcrowe's Avatar
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    Re: Larger-Smaller memory cards...

    Dave, It seems as if card speeds can be directly related to camera types.

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    Re: Larger-Smaller memory cards...

    Quote Originally Posted by rpcrowe View Post
    Thanks John. I suspected as much. This was one of those "interesting" but useless questions which keep popping into my brain!
    Not useless at all. I've always felt that using smaller cards made more sense. Using multiple smaller cards means if there is an issue (corrupt card, lost card, etc.) then less photos are at risk. But if there was a performance issue, then that might mitigate that risk. So I was/am interested to see the responses.

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    Re: Larger-Smaller memory cards...

    SD cards can transfer data either as a single bit data stream or a 4 bit wide data transfer. I assume all SLR cameras use the 4bit mode but some may not. The memory is arranged so that access is via blocks and I understand they must be written or read as complete blocks. With the larger memory devices these blocks may be 2 or 4 times bigger than in the smaller devices so if a record/file only needs a small part of the block the whole block still needs to be transferred (within the SD card) regardless.

    I do not know the overall timing of transferring data between a SD card and the computer but it is possible that block size within the SD card is one of the factors.
    Last edited by pnodrog; 3rd July 2013 at 06:15 AM.

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    Administrator Manfred M's Avatar
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    Re: Larger-Smaller memory cards...

    I believe smaller cards (under 4GB; practically speaking 2GB cards and smaller) use shorter memory address pointers (32-bit); anything larger uses 64-bit, so in theory, the smaller cards should be slightly faster.

    I shoot the largest, fastest CF cards I can afford (right now that means 64GB 800x Lexar Professional) and notice card speed more during download operations than when the camera writes data to the card; but then, I rarely shoot burst mode, so the camera's buffer has lots of time to dump the data.

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    Re: Larger-Smaller memory cards...

    I'm fairly certain advancements in technology would completely overwhelm any possible difference between 32 and 64 bit pointers.

    I don't believe that size would make any difference in read/write speeds. Memory cards certainly work differently than RAM. With a computer, extra RAM speeds up the whole system, but with cameras we're just talking about reading/writing to memory. I think the better analogy would probably be the hard drive. You can have a hard drive that is both faster and higher capacity.

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    Re: Larger-Smaller memory cards...

    The read/write times usually refer to the speed of the flash/e2ram memory modules within the SD/CF card, not the speed of data transfer between the computer (or camera) and the card or the card's processor's speed of performing or buffering the blocks of read/write data to its memory. We assume designers/manufactures ensure that these transfers are reasonably synchronized but some of the cheaper devises may have truthful but misleading specifications. It is a bit like city roads having a specified 30m/h speed limit and a driver expecting to have traveled 30 miles after an hour of driving. Some cities are better designed than others.

    The performance at the bottom end of the market is driven by price first with technology advancement a distant second. You tend to get what you pay for.
    Last edited by pnodrog; 4th July 2013 at 12:29 AM.

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    Re: Larger-Smaller memory cards...

    Quote Originally Posted by blakemcguire View Post
    I'm fairly certain advancements in technology would completely overwhelm any possible difference between 32 and 64 bit pointers.
    CF cards appear as a (ATA) hard drive, with 28-bit addressing, and it's blocks that are addressed, not single bytes, so the difference isn't there.
    What is happening is that a write requires some fairly complicated operations, called 'wear levelling', in order to assure that all blocks are used equally. For a large card, that could mean more data to check (more blocks) and perhaps more to shuffle around. The use of the card might also play a role: a card that's filled up and then emptied will have to do less shuffling than a card where some images are added, then some are removed , and a few stay a long time on the card.


    [/quote]I don't believe that size would make any difference in read/write speeds. Memory cards certainly work differently than RAM. With a computer, extra RAM speeds up the whole system, but with cameras we're just talking about reading/writing to memory. I think the better analogy would probably be the hard drive. You can have a hard drive that is both faster and higher capacity.[/QUOTE]
    Extra RAM will speed up the system only if the available memory was too small to hold all programs and data in RAM (i.e. swap files/partitions were actively used). As long as there is enough RAM to hold the active programs, extra will not speed up the system (so putting 16 GB in a system that only uses 8GB is a waste of money).

    What can happen is that the first set of RAM modules was badly placed. In that case, adding another set of RAM modules will speed up the system (DDR2 or DDR3) (don't laugh, that's what happened to me with my current computer, the assembler had placed the second RAM module in the wrong slot...).

    Comparison with a hard drive also goes only so far, as a traditional hard drive doesn't need 'wear levelling': it has many more erase/write cycles before failure, where flash memory has only a 'limited' number of cycles (1M was cited, and that also holds for the directory blocks, which are written at every write or delete operation, a reason not to delete individual files from the card).

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    Administrator Manfred M's Avatar
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    Re: Larger-Smaller memory cards...

    Quote Originally Posted by revi View Post
    CF cards appear as a (ATA) hard drive, with 28-bit addressing, and it's blocks that are addressed, not single bytes, so the difference isn't there.
    What is happening is that a write requires some fairly complicated operations, called 'wear levelling', in order to assure that all blocks are used equally. For a large card, that could mean more data to check (more blocks) and perhaps more to shuffle around. The use of the card might also play a role: a card that's filled up and then emptied will have to do less shuffling than a card where some images are added, then some are removed , and a few stay a long time on the card.


    I don't believe that size would make any difference in read/write speeds. Memory cards certainly work differently than RAM. With a computer, extra RAM speeds up the whole system, but with cameras we're just talking about reading/writing to memory. I think the better analogy would probably be the hard drive. You can have a hard drive that is both faster and higher capacity.

    Extra RAM will speed up the system only if the available memory was too small to hold all programs and data in RAM (i.e. swap files/partitions were actively used). As long as there is enough RAM to hold the active programs, extra will not speed up the system (so putting 16 GB in a system that only uses 8GB is a waste of money).

    What can happen is that the first set of RAM modules was badly placed. In that case, adding another set of RAM modules will speed up the system (DDR2 or DDR3) (don't laugh, that's what happened to me with my current computer, the assembler had placed the second RAM module in the wrong slot...).

    Comparison with a hard drive also goes only so far, as a traditional hard drive doesn't need 'wear levelling': it has many more erase/write cycles before failure, where flash memory has only a 'limited' number of cycles (1M was cited, and that also holds for the directory blocks, which are written at every write or delete operation, a reason not to delete individual files from the card).
    Revi - This is a very good explanation of how NAND memory controllers work. In many ways, there are parallels with writing large files to badly fragmented hard drives and the noticeable slow down that can occur as the read / write heads move around to the appropriate empty blocks.

    As to your computer having memory set up in the wrong slots; I’m surprised that it even booted up. The ones I’ve used just give a boot error. It’s nice to see that some motherboard manufacturers have smartened up and colour code the memory slots to reduce the likelihood of this happening.

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    Re: Larger-Smaller memory cards...

    Quote Originally Posted by GrumpyDiver View Post
    Revi - This is a very good explanation of how NAND memory controllers work. In many ways, there are parallels with writing large files to badly fragmented hard drives and the noticeable slow down that can occur as the read / write heads move around to the appropriate empty blocks.
    thank you

    As to your computer having memory set up in the wrong slots; I’m surprised that it even booted up. The ones I’ve used just give a boot error. It’s nice to see that some motherboard manufacturers have smartened up and colour code the memory slots to reduce the likelihood of this happening.
    It's a DDR2 system, and the modules were in A1 and A2, where they would have been better in A1 and B1 (or the other way around, I'd have to check the manual...). But those were the only two valid possibilities
    But yes, the system booted. But I'm curious, and opened the box and manual to check...

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    Administrator Manfred M's Avatar
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    Re: Larger-Smaller memory cards...

    Quote Originally Posted by revi View Post
    It's a DDR2 system, and the modules were in A1 and A2, where they would have been better in A1 and B1 (or the other way around, I'd have to check the manual...). But those were the only two valid possibilities
    But yes, the system booted. But I'm curious, and opened the box and manual to check...
    That makes sense - some DDR2 systems do get a boost that way by splitting the read / write across two different banks. I was thinking DDR3, where this is a requirement.

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