15 May
2014
15 May
'14
10:24 p.m.
On 5/15/2014 10:14 PM, Keith Monahan wrote:
On 5/15/2014 11:52 PM, David Riley wrote:
But small cards are hard to find, at least for me in Canada.
Don't get me wrong, I think his design is
pretty great. I just
figure that's where most of the bottleneck is coming in. And,
unlike everyone else (including me), he got it out the door
instead of optimizing it to death in his head. :-)
The creator explained the bottlenecks, which seem simple enough to me:
* He's using the 1-bit interface instead of the 4-bit. (I seem to recall
the 4-bit sdcard interface has some proprietary undocumented nature to
it, but that's not the only hurdle related to using the 4-bit interface)
* He's not using the maximum frequency on the SDCARD. The current uC
implementation is driving things around 15mhz (performance numbers on
his site were taken @ 18mhz, which is why he is seeing slightly better
numbers) The sdcard interface can do 25mhz.
* Not all cards are made equal, especially when it comes to
"erase-block-size", and small writes can force the card to (internally)
re-write much larger blocks. Using SMALLER cards which have smaller
erase-block-sizes will actually perform better than using the latest
fattest cards. Keith