Which SD card is tested by NI and can reach 2MB/s per card?

[Ex-NISH2]

Which SD card is tested by NI and can reach 2MB/s per card?

I used Sandisk Ultra II, which claims 10MB/s write speed, but only get about 0.6MB/s with 9802.  I think the problem is due to the writing algorithm.  Sandisk benchmark is tested with large data block (file size), while NI FPGA is writing word by word.

So, my questions are:

1. which SD card model is certified by NI?  You can find the claim of speed in the users manual of 9802, but I can not find the list of 'certified' models.

2. How to get the best benchmark of 9802?  Should I write in U8, U16, or U32?

Regards

[hrh1818]

On Jul 5, 2:10 am, Ex-NISH2 <x...@no.email> wrote:
> Which SD card is tested by NI and can reach 2MB/s per card?
> &nbsp;
> I used Sandisk Ultra II, which claims 10MB/s write speed, but only get about 0.6MB/s with 9802.&nbsp; I think the problem is due to the writing algorithm.&nbsp; Sandisk benchmark is tested with large data block (file size), while NI FPGA is writing word by word.
> &nbsp;
> So, my questions are:
> &nbsp;
> 1. which SD card model is certified by NI?&nbsp; You can find the claim of speed in the users manual of 9802, but I can not find the list of 'certified' models.
> 2. How to get the best benchmark of 9802?&nbsp; Should I write in U8, U16, or U32?
> &nbsp;
> Regards

SD cards are not designed for random access read/write. When you
write only one byte at a time the SD controller needs to read a block
of data change one byte in the block and then write the block of data
back to the card. National Instruments doesn't provide the
qualifications that go with its 2 megabyte per second specification
but 2 to one says it is not random access read write. If you want
higher speeds than 0,6 megabytes per second you will have to buffer
your data into block size chunks.

Howard

[Ex-NISH2]

Sorry, I didn't clarify that I am using LV FPGA and writing the SD card in the NI cRIO 9802.  I am using and modifying the write file example of LV FPGA for 9802.

The 9802 driver only provides one write method in LV FPGA, while it can take U8, U16 and U32.  I tried U8 and U32 yesterday, and got the same benchmark (in Bytes/sec).

I want to know how can I get the SD card, which has the same speed as the 9802 specification.

[hrh1818]

On Jul 6, 4:10 am, Ex-NISH2 <x...@no.email> wrote:
> Sorry, I didn't clarify that I am using LV FPGA and writing the SD card in the NI cRIO 9802.&nbsp; I am using and modifying the write file example of LV FPGA for 9802.
> The 9802 driver only provides one write method in LV FPGA, while it can take U8, U16 and U32.&nbsp; I tried U8 and U32 yesterday, and got the same benchmark (in Bytes/sec).
> I want to know how can I get the SD card, which has the same speed as the 9802 specification.

At this point I suggest you send an E-Mai to the Technical Support
Group at National Instruments. National Instruments doesn't supply
enough information about their 2 megabytes per second read/write
specification for the 9802 to enable one to know or not know if it
applies when writing one two or 4 bytes at at time. I don't believe
the specification applies when writing one, two or 4 bytes at a time.
You believe it does. Hence I suggest your next step should be to
contact National Instruments.

Howard

[Ex-NISH2]

Thanks.

I hope NI guys will reply.

I have 2 NI SD cards, and they actually reach 2MB/s with the same program which I got 0.8MB/s with Sandisk extreme III.

Posting on this forum is the fastest way to get support from NI gulus, if you are not in NI.

[hrh1818]

On Jul 6, 10:40 am, Ex-NISH2 <x...@no.email> wrote:
> Thanks.
> &nbsp;
> I hope NI guys will reply.
> &nbsp;
> I have 2 NI SD cards, and they actually reach 2MB/s with the same program which I got 0.8MB/s with Sandisk extreme III.
> &nbsp;
> Posting on this forum is the fastest way to get support from NI gulus, if you are not in NI.

The 9802 storage module seems to be pretty expensive for being just a
box to hold SD cards and National Instruments doesn't provide any
information on their SD cards. I suspect along about now you are
getting frustrated with how little information National Instruments
provides on these two products. Cheer up better days are coming.

Howard

[Bassett_Hound]

Ex-NISH2,

The NI Recommended SD cards are linked from the NI 9802 Product Page and are the following:

780245-01 512 MB SD Card, Industrially Rated  Price $  99.00      
780246-01 2 GB SD Card, Industrially Rated      Price $199.00  

The 2MB/sec specification is for the NI Recommended SD cards.  I do agree that it should really be specified as a typical spec so will make sure the manual gets updated properly.  I have seen other SD cards perform at much slower throughput rates so if your not meeting the specification with third party cards you'll want to use the NI card.  Additionally, the 2 MB/sec is only when accessed from the FPGA and not through the Real-Time Mount support.  I have attached an image of what I've used in the past to benchmark the 2 MB/sec speed as well.  You'll notice it just writes U32 values with the write method.

I hope that clarifies things a bit.  Let me know if you have any other questions or feedback.

Regards,

Basset Hound

Message Edited by Bassett Hound on 07-07-2008 01:44 PM

[hrh1818]

On Jul 6, 10:40 am, Ex-NISH2 <x...@no.email> wrote:
> Thanks.
> &nbsp;
> I hope NI guys will reply.
> &nbsp;
> I have 2 NI SD cards, and they actually reach 2MB/s with the same program which I got 0.8MB/s with Sandisk extreme III.
> &nbsp;
> Posting on this forum is the fastest way to get support from NI gulus, if you are not in NI.

Thank you for posting the reply you received from National
Instruments. I noticed Basset Hound didn't tell you what was unique
about National Instruments SD cards and why they seemed to be so much
faster. One thing you might try if you dislike paying National
Instruments price for a SD card is a Sandisk Extreme III SD card.
See:
http://www.sandisk.com/Products/Item(1973)-SDSDX3-2048-901-SanDisk_Extreme_III_SD_2GB.aspx
It has a minimum sequential read write speed of 20 megabytes per
second and a list price of $39.99 for a 2GB card.

Howard

[Ex-NISH2]

I tried.  It is 0.8MB/s.