http://forum.arduino.cc/index.php?topic=220918.msg1606560#msg1606560
That could be useful for people who want to overcome the sdcard's write latency issue and need a caching before writing the stuff onto the sdcard..
That is great performance at low cost.
It's all many users would need for storage. Could use a small RAM disk filesystem.
Unfortunately FAT16 is not quite right since it is fundamentally block oriented. My new FAT16/FAT32 library would work with only a simple driver but it would kill performance.
Looks like it is limited to 3.3V??
A very thin file-like library would make it easy to use in applications. Many commercial RTOSs have such a program but I have not found an open source program.
I put a lot of Microchip SPI 128 KB SRAM chips on a board and want one for that.
Could use a small RAM disk filesystem.
The module is primarily used as a swap and filesystem for retrobsd.org project (pic32mx, accessed via its ext mem bus).
# ls -l
total 28
drwxr-xr-x 2 root 1024 Jan 30 13:59 lost+found
-rwxr-x--x 1 root 26412 Jan 30 14:01 rc4_dropn
-rwxr-x--x 1 root 161 Jan 30 14:01 testrc
# time dd bs=16k count=300 if=/dev/zero of=AAA
300+0 records in
300+0 records out
1.1 real 0.0 user 1.1 sys
# ls -l
total 4828
-rw-r----- 1 root 4915200 Jan 30 18:11 AAA
drwxr-xr-x 2 root 1024 Jan 30 13:59 lost+found
-rwxr-x--x 1 root 26412 Jan 30 14:01 rc4_dropn
-rwxr-x--x 1 root 161 Jan 30 14:01 testrc
#
It shows 4.9MB/1.1sec filesystem write speed with the ramdisk.
Looks like it is limited to 3.3V??
Yes.
I put a lot of Microchip SPI 128 KB SRAM chips on a board and want one for that.
You would need a lot of 128kBytes sram chips to emulate the above ramdisk 
I used eight SRAM chips for a MB and was thinking about 16. They are nice since they are nonvolatile with a coin cell and are about $2 each. You need to decode chip select to save pins. 3 to 8 is less than a $1.
OK if you use a few but never for 8 MB.
3.3 V, How fast could it be with a STM32? That's the 3.3V ARM processor I like. Probably not worth it since the big STM32 has so much RAM for buffer so latency is not a problem. I can write to an SD at several MB/sec.
How fast could it be with a STM32? That's the 3.3V ARM processor I like.
Me too. My favorite is F4 I've been toying most. The sram used is with 70ns access time one. So that is the limitation. With 6ns clock the overhead will be lower. I guess 6-8MBytes/sec would be feasible (filesystem rd/wr access). The physical limit of the ramdisk itself is ~12.5MB/sec.
With F4 you may utilize its memory bus, with sram up to 64MB I think. The new F427..439 series has got an sdram interface (144pins up)..