133X lexar cards (20MB/s)

S

stabwound

Well-known member
http://www.dpreview.com/

At 20 megabytes/sec, there may not be a need to raid memory to get P2 speeds.

Maybe some enterprise will somehow adapt CF cards (I read somewhere they're in the 8 gig range already) for use in the P2 slot.
 
I'm about to order an USB-Stick that can handle up to 27 MB/sec writing speed, 4 GB for 350 Euros. But this is the maximum transferrate you get under best circumstances.
P2 cards have to record about 17 MB/sec continuously without the slightest delay.

If you ask a SD card vendor what the approved minimum transferrate of their card is, it will be maybe a lot lower that 20 MB/sec.
 
MarcusX said:
I'm about to order an USB-Stick that can handle up to 27 MB/sec writing speed, 4 GB for 350 Euros. But this is the maximum transferrate you get under best circumstances.
P2 cards have to record about 17 MB/sec continuously without the slightest delay.

If you ask a SD card vendor what the approved minimum transferrate of their card is, it will be maybe a lot lower that 20 MB/sec.
Click to expand...

Holy.

I forgot about terms like "Max burst speed rate" and "minimum sustained transfer rate" , which referred to hard drives, might also be applicable to flash memory.:huh:

Always thought flash memory was constant when it comes to speed.
 
Well, Dpreview has tested the new card against the old speedchamp from SanDisk:

cardbus-cf-graph.gif


This is the maximum speed in a PCMCIA Cardbus Compactflash reader.
Well below 20 MB/s. Gives a glimpse of why Panasonic needs to RAID 4 chips in the P2.

Also all cards over 2 GB must use FAT 32 which is slover due to a larger cluster size.

The graf is from the test found here:
http://www.dpreview.com/news/0601/06011701lexar133xcards.asp
 
stabwound said:
Always thought flash memory was constant when it comes to speed.
Click to expand...

Maybe it is, I don't know. Jan said only 1% of the current available SD-cards are suitable for P2. The demands for a P2 cards are different than for a SD-Cards in a still camera or a mass-storage device.

Maybe the access time is the problem. When there's a chance of 1:100,000 it takes longer than 1/60 second for recording a frame over several minutes, the cards are useless for P2.
 
I did some testing HDD vs. USB 2.0 Flashmemory to learn more about the characteristics of flash memory.
I wrote a simple script, which transfers a package of 300,000 Bytes from RAM to storage device about 1000 times (286 MB) and measured the time of each packet.
The HVX200 records a packet of ca. 300,000 Bytes every 16 msec (60 fps).
I don't know if this setup is really reliable.

HDD RAID0, write cache enabled: 85 MB/sec, max. 18 msec, average 3 msec writing the 300.000 B. packet.
USB 2.0 HDD, write cache disabled: 20,7 MB/sec, max. 47 msec, average 14 msec
USB 2.0 Flashmemory (Kingston Elite 512 MB), write cache disabled: 8,4 MB/sec, max. 123 msec, average 15 msec.

The harddisks performed pretty stable, unlike the memorystick. The transfer even stopped sometimes about 1-2 seconds before continuing. The Kingston Elite is rated "24 MB/sec reading speed".
If the SD-cards within the P2-card have some kind of RAID0, the access times gets even worse, because the camera has to wait for all 4 cards to be able to write a new frame.
I wonder how many frames the HVX200 can buffer before writing to P2.
 
Yes the P2 equipment definitely has a ram buffer , even a entry level digital still camera has a buffer.

Isn't it around 10 secs it will buffer in the 25 Mb prerecord setting? that should be at least 35 MB ram.
 
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