Thread: Is SD slower than CF????
07-20-2003, 09:55 PM #1
Is SD slower than CF????
An additional feature of SD is the so it's slower than CompactFlash according to Chris O'Herrera.
If that is true, why would I want to buy SD over CF? Would'nt any programs installed to the SD card load slower?????
07-21-2003, 08:16 AM #2
Can anyone help me with this?
I am trying to decide whether to buy an SD card to store my programs on. If it is slower than my CF card I will use it instead.
07-21-2003, 10:02 AM #3
I think the general idea is to get an SD memory card purely to leave the CF slot free for things like W-LAN, GPS, CF camera, etc...
SD-IO allows some expansion devices, but CF is king of the expansion device options at the moment, so buying an SD memory card might be more expensive and perform less well than a top range CF memory card, but at least you have the CF slot free for other cards.
If you don't need expansion devices, you can fill both slots with memory cards, if you like.
07-21-2003, 10:26 AM #4
It isn't THAT much slower. It is only noticealbe if you are moving 10+ MB, espescially over ActiveStync. I keep all of my programs on my 128MB sd card, and all of my larger multimedia files on my CF card. I always have my sd card in, but I plan on getting a WiFi CF card at some point.
07-21-2003, 10:26 AM #5
CF is faster than SD, but you will only see some difference when trying to copy big files. If you just install programs and small files to the SD, you won't really see any speed improvement over a CF card.
Current PDA: HP 4155 + Sprint PM325 = Wireless Heaven
Past PDA's: Palm III, Jornada 525, Jornada 547, iPaq 3760, iPaq 3835, ipaq 3670, iPaq 3970, Toshiba e740, iPAQ 5455, iPAQ 2215.
07-21-2003, 10:56 AM #6
- Join Date
- Jun 2003
What I find interesting is all of the reviews and head-to-heads (probably marketing) that talk about SD being faster than CF. Go figure. Probably what some of you have said: nominal throughput is slower, but burst on SD may be faster.
07-21-2003, 04:09 PM #7
The problem is SD cards currently only have vague descriptions of their speed like, Fast, Very Fast, High speed, which doesn't tell you much.
CF on the otherhand almost always has the X rating that we are used to from cd-roms.
I think lexar is the first to give their high speed SD cards a 32x label.
In actual testing it doesn't seem like the PDA can use all that speed... Anyone have a fast CF card to test? I think Ogreboy tested an 8x CF card and he got about 6.5x out of it. And slightly slower for his 32x SD card...
to calculate the X rating just take the k/s and divide by 150k/s. So 4.8 mb/s=4800k/s. 4800k/s / 150k/s = 32x.
07-21-2003, 04:48 PM #8
if you take a high-end SD card (512Mb) and a high-end CF Card (1 Gig) you will find out that acording to the specs in MB/sec the SD card is much faster. There was a recent discusion about this and a gave a few links that had a table about this comparing SD to cf, ms etc etc. Search and you will find it. Also someting to note is that a 512MB SD card is 10 times faster than a 256MB SD, acording to the specs and also to real life tests.
07-21-2003, 05:39 PM #9
Paris, Do you have a USb 2.0 card reader by chance? Then you could test the max sustained read/write speed of your 512mb card. In the other thread you said it took 25 seconds to backup 16mb, which is actually very slow. (650k/s / 150 = 4.26X). This 650k/s is no where near the 4.8mb/s the lexar 32x SD cards claim and no where near the 10mb/sec - 20mb/sec these high capcity cards are said to have int he links you gave in the other thread.
I've only seen extensive testing of the lexar 32x 256mb card and a 8x 1gig compact flash card. The compact flash card had slightly higher transfer rates between system memory to the card (i recall around 6.5x). Transfering from a computer through the cradle hit some bottleneck that was about 1x or 150k/s transfer rate.
here is the thread:
final results: 18.5 meg file transfered
Mem->SD: 25 seconds (4.9x)
SD->Mem: 28 seconds (4.4x)
Mem->CF: 18 seconds (6.8x)
CF->Mem: 35 seconds (3.2x)
HD->SD: 101 seconds (1.2x)
HD->CF: 105 seconds (1.17x)
I would expect both cards to perform near their max in a usb 2.0 card reader (usb 1.1 would max at 8.33x), but it appears the pocket pc cannot off max speeds.
Anyone have any cards to test? just time how long it takes to transfer a good sized file from the system memory to a sd card.
Paris since you have a 512mb maybe you could test and see if your SD speeds are faster than the 256mb card that should be 32x, but only gets 4.5x on the 2215.
07-21-2003, 05:49 PM #10
Peppe your results are very nice!!!!!!! I dont have a USB 2 reader but i can run the test if you send one to Cyprus (or come on to Cyprus for vacations and will use your reader to do the test). Anyway i like your results since i did test a 256 vs the 512 and the 512 SD was 5 or 10(dont remeber exactly) times faster than the 256. This was acording to the specs but most importantly results of real tests i did. If this is the case then you will find that a 512 SD will outperform the 1 Gb CF you have tested.
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