Compact Flash Card Driver - How fast?

[jcgxxx]

Was browsing tru the forum but cant seem to find any information on how fast the access speed (read/write) is for CF cards - especially the 30X ones when used with CF card driver

Anyone has any data on this?

MS Read 2.45MB/Sec Write 1.5MB/Sec
CF card Fast 30X 4.5MB/s
MS Pro: Transfer Rate: 160Mbps (20MB/sec) (Theoretical maximum
Minimum Write Speed: 15Mbps

How fast is the MS Pro on the NX 70?

[CliePet]

> Was browsing tru the forum but cant seem to find any information on how fast the access speed (read/write) is for CF cards - especially the 30X ones when used with CF card driver

People have posted VFSMark numbers, but I find them only marginally useful.

> Anyone has any data on this?

For real "MB/s" rates, check this thread (ie. the last post on the first page)

http://www.cliesource.com/forums/showthread.php?s=&threadid=12285

My best speed (30X Transcend CF card) was 924KB/s read, 525KB/s write

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> MS Read 2.45MB/Sec Write 1.5MB/Sec
> CF card Fast 30X 4.5MB/s
> MS Pro: Transfer Rate: 160Mbps (20MB/sec) (Theoretical maximum
> Minimum Write Speed: 15Mbps

These are theoretical maximums and bear little resemblance on real world speeds (in PDA or non-PDA devices).

If you are getting 1MB/sec read speeds, consider yourself lucky.

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>How fast is the MS Pro on the NX 70?

This has been discussed in other threads.
The MS Pro max specs are once again misleading (since the CLIE doesn't support the faster data path)

[jcgxxx]

Interesting : got this reply from Sony singapore helpdesk giving high read write for NX70 - i.e able to maximise the MS's limit, but Will not get any faster with the MSPro.


From: Helpdesk, Vaio [SMTP:Vaio-Helpdesk@ap.sony.com]
Sent: Wednesday, 07 May, 2003 2:42 PM
Subject: RE: Memroy stick

Dear Sir,

Thank you for your e-mail.

For your information, the PEG-NX70V/G's reading speed is 19.6 Mbps and writing speed is 14.4 Mbps.

We hope the information is of use to you. Apologies for the inconvenience caused.

In conclusion, should you have any enquiries, concerns or feedback, please do not hesitate to e-mail or contact our hot-line at 6544-8600 (Option 1).

Best regards,

[CliePet]

> MS Read 2.45MB/Sec Write 1.5MB/Sec
...
> For your information, the PEG-NX70V/G's reading speed is 19.6 Mbps and writing speed is 14.4 Mbps.

These are essentially the same "theoretical maximum" numbers (8 Mb/sec = 1 MB/sec). The same caveat applies

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DIGRESSION:
My *guess* is they are taking the design maximum for a normal memory stick serial bus (SCLK max of 20MHz) and assuming a minimal overhead to get the 19.6Mb/sec (2.45 MB/sec) read number.

I'm not sure where they got the write number from. Since the two sources can't agree whether it is 1.8MB/sec or 1.5MB/sec that tells you something. The theoretical maximum bus speed is still around 20MHz (~2.5MB/sec) with no verification, but the real limit is how fast the flash chips can be erased/programmed.

BTW: I also suspect they may not be running the SCLK at full 20MHz speed based on some of my measurements, but I haven't scoped the actual PDA to be sure. Earlier specs I read mentioned a max of 10 -> 15 MHz.

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So once again ignore the theoretical maximums and rely on actual measurements (and ideally ones that you make yourself for your unique situation)

Typically what you get in reality is something much slower -- about 1/2 the theoretical maximum.

BTW: This is true for MS and CF usage in many applications, not just the CLIE.
The one field where write speed tends to matter the most is cameras, and you will typically find more efficient implementations there.