Sd Read And Write Speed

[Spadoof]

Dear Readers,

Just wondering if anyone knew the read/write speed cap for the pandora. Also I understand the fast the mems card speed (Read and write), the better things proform (Loading time saving time), but what are other impacts the speed of a memory card have the devices proformance.

Thanks,
-Spadoof :gp2x

 

[Squidge]

Guess we'll find out when some Pandora's ship...

 

[MWeston]

24MB/s based on a 48MHz clock, 4 bit SDIO

 

[atomicthumbs]

Guess we'll find out right now

 

[Squidge]

24MB/s based on a 48MHz clock, 4 bit SDIO

Is that theoretically, or tested?

 

[MWeston]

Just the specs on paper but the SD peripherals have their own dedicated caches so it should be quite speedy.

Of course 24MB/s assumes no protocol overhead which isn't possible so real transfers would be slightly less with command transfers and such but this is the theoretical for the data transfer section.

 

[fusion_power]

24MB/s based on a 48MHz clock, 4 bit SDIO

Wow, this sounds like it will be at least a "LITTLE BIT" more than the GP2X SD-Speed and maybe you know the SD read/write -"Fun" onto the GP2X.

I don't have a SDIO SD (Yet) but even the 5-10 MB/sec of my current Standard SD Cards would be more than enough to make me happy.
I usualy have 400-500 kb/sec read/write when I'm using my GP2X via USB cable to put Data from PC onto the Handheld. (Thats not even USB 1.1 Speed afaik - again GPH did a great job there :lol: )

 

[Squidge]

Just the specs on paper but the SD peripherals have their own dedicated caches so it should be quite speedy.

Of course 24MB/s assumes no protocol overhead which isn't possible so real transfers would be slightly less with command transfers and such but this is the theoretical for the data transfer section.

I managed to get 10MB/sec by using DMA on the MMSP2+, so hopefully the OMAP is a little faster than that. With the overhead of Linux and the like, lets hope for around the 15MB/sec mark.

 

[Vorporeal]

What kinds of SD cards does this (theoretical) 24MB/sec apply to? I'm not too knowledgeable in terms of memory-card storage, but I know that SDHC cards have classes that seem to have some sort of effect on their data transfer rates.

 

[Squidge]

A class 6 SD Card has a speed of 6 MB/s or higher at the best fragmented state.

 

[Vorporeal]

A class 6 SD Card has a speed of 6 MB/s or higher at the best fragmented state.

So what kind of card would achieve this 24MB/sec?

 

[Balzac2m]

A class 6 SD Card has a speed of 6 MB/s or higher at the best fragmented state.

So what kind of card would achieve this 24MB/sec?



Panasonic (for example) has a card which gets "up to" 20 MB/.

 

[Kramy]

So what kind of card would achieve this 24MB/sec?

A class 6.

Nah...actually...a 150x (or higher) regular SD might.

I believe the idea with Class 6 was, by standardizing speeds to "> 6MB/sec", developers start coding stuff for "<= 6MB/sec", because everyone is only guaranteed 6MB/sec.

 

[Holokauston]

So what kind of card would achieve this 24MB/sec?

A class 6.

Nah...actually...a 150x (or higher) regular SD might.

I believe the idea with Class 6 was, by standardizing speeds to "> 6MB/sec", developers start coding stuff for "<= 6MB/sec", because everyone is only guaranteed 6MB/sec.


when you load from the SD yes, you have to take RAM in to consideration as well ;P

SDRAM DDR-333 maxes out at 2700 MB/s

 

[Squidge]

Don't forget that there is protocol overhead too, and the fact that the sd data has to be written somewhere, and the device has to do other jobs too.

Once real Pandora are out there, we can find out the realistic speeds.

 

[ldesnogu]

SDRAM DDR-333 maxes out at 2700 MB/s

LP DDR interface of OMAP35x is 16 or 32 bit wide. I also doubt it is 333 MHz, it would rather be 133 or 200 MHz.
So at the very best it would be 2 (double data rate) x 4 bytes (32 bit interface) x 200 (MHz) = 1.6 GB/s.
I think we won't see that by far

 

[Holokauston]

SDRAM DDR-333 maxes out at 2700 MB/s

LP DDR interface of OMAP35x is 16 or 32 bit wide. I also doubt it is 333 MHz, it would rather be 133 or 200 MHz.
So at the very best it would be 2 (double data rate) x 4 bytes (32 bit interface) x 200 (MHz) = 1.6 GB/s.
I think we won't see that by far

DDR333 is 166Mhz ??
http://en.wikipedia.org/wiki/DDR_SDRAM

 

[ldesnogu]

DDR333 is 166Mhz ??
http://en.wikipedia.org/wiki/DDR_SDRAM


My bad
Anyway your bandwidth figure was assuming 64 bit interface, which it can't be