speeds of SD vs. SDHC cards

Discussion in 'Digital Photography' started by yawnmoth, Dec 7, 2007.

  1. yawnmoth

    yawnmoth Guest

    According to <http://en.wikipedia.org/wiki/Sd_card#Speeds>, SD cards
    come in four different possible speeds - 0.9mb/s, 6mb/s, 10mb/s, and
    20mb/s. According to <http://en.wikipedia.org/wiki/Sd_card#SDHC>, SDHC
    cards come in three different possible speeds - 2mb/s, 4mb/s, and 6mb/
    s. From that, it looks like the fastest SDHC card is slower then the
    fastest HD card. Is that correct or is there something I'm missing?
    And if it is correct... why? According to the article, "SDHC uses a
    different memory addressing method". Is that what's slowing it down?
     
    yawnmoth, Dec 7, 2007
    #1
    1. Advertising

  2. In article <86b5b4cd-a8a2-4f3f-9ccf-0a9107e00311
    @w40g2000hsb.googlegroups.com>, says...
    > According to <http://en.wikipedia.org/wiki/Sd_card#Speeds>, SD cards
    > come in four different possible speeds - 0.9mb/s, 6mb/s, 10mb/s, and
    > 20mb/s. According to <http://en.wikipedia.org/wiki/Sd_card#SDHC>, SDHC
    > cards come in three different possible speeds - 2mb/s, 4mb/s, and 6mb/
    > s. From that, it looks like the fastest SDHC card is slower then the
    > fastest HD card. Is that correct or is there something I'm missing?
    > And if it is correct... why? According to the article, "SDHC uses a
    > different memory addressing method". Is that what's slowing it down?



    No, they're mixing apples and oranges.
    The SD speeds listed are _READ_ speeds. The _WRITE_ speed for and SD
    card is typically 1/2 to 1/10 of the read speed. Note also that many of
    the speeds published on WP are in MB (megaBYTES), not Mb (megaBITS) per
    second.

    For SDHC, the "class" rating is for _WRITE_ speed:

    Class 2: >= 2 MBYTES/sec
    Class 4: >= 4 MBYTES/sec
    Class 6: >= 6 MBYTES/sec

    --Gene
     
    Gene S. Berkowitz, Dec 10, 2007
    #2
    1. Advertising

  3. Gene S. Berkowitz <> writes:
    >In article <86b5b4cd-a8a2-4f3f-9ccf-0a9107e00311
    >@w40g2000hsb.googlegroups.com>, says...
    >> According to <http://en.wikipedia.org/wiki/Sd_card#Speeds>, SD cards
    >> come in four different possible speeds - 0.9mb/s, 6mb/s, 10mb/s, and
    >> 20mb/s. According to <http://en.wikipedia.org/wiki/Sd_card#SDHC>, SDHC
    >> cards come in three different possible speeds - 2mb/s, 4mb/s, and 6mb/
    >> s. From that, it looks like the fastest SDHC card is slower then the
    >> fastest HD card. Is that correct or is there something I'm missing?
    >> And if it is correct... why? According to the article, "SDHC uses a
    >> different memory addressing method". Is that what's slowing it down?


    >No, they're mixing apples and oranges.
    >The SD speeds listed are _READ_ speeds. The _WRITE_ speed for and SD
    >card is typically 1/2 to 1/10 of the read speed. Note also that many of
    >the speeds published on WP are in MB (megaBYTES), not Mb (megaBITS) per
    >second.


    That may be true for some SD cards. But the Sandisk "Extreme III" cards
    are rated by Sandisk as 20 MBytes/sec. minimum for both read and write.
    That's faster than SDHC class 6.

    So it looks like most SDHC cards are faster than most but not all SD
    cards.

    By the way, are there SDHC cards smaller than 4 GB? I was looking
    yesterday in a Best Buy and could not find any - anything 2 GB and lower
    was SD, not SDHC.

    >For SDHC, the "class" rating is for _WRITE_ speed:


    >Class 2: >= 2 MBYTES/sec
    >Class 4: >= 4 MBYTES/sec
    >Class 6: >= 6 MBYTES/sec
     
    Dave Martindale, Dec 12, 2007
    #3
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Steve

    Kodak Z700 - does it support sdhc cards?

    Steve, Aug 28, 2007, in forum: Digital Photography
    Replies:
    3
    Views:
    710
    Ron Baird
    Sep 4, 2007
  2. Sitara Lal

    Nikon D80 / D50 & Kingston SDHC cards

    Sitara Lal, Oct 19, 2007, in forum: Digital Photography
    Replies:
    2
    Views:
    453
  3. PC

    Compatibility with SDHC cards??

    PC, Dec 11, 2007, in forum: Digital Photography
    Replies:
    2
    Views:
    283
  4. Transcend SDHC Cards

    , Jan 5, 2008, in forum: Digital Photography
    Replies:
    3
    Views:
    308
  5. NameHere
    Replies:
    0
    Views:
    1,634
    NameHere
    Mar 27, 2010
Loading...

Share This Page