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32MB Fuze V1, Checksum error

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sss:
Alright, some free time opened up and I've been thinking about this again.

Funman, while I appreciate the help, there are a few things that remain unclear.

--- Quote ---The bootloader needs to use the SDRAM since we added USB support, because else it wouldn't fit in the 320kB IRAM.
--- End quote ---

--- Quote ---You must of course update the bootloader while the original memory chip is in place
--- End quote ---

You seem to be telling me I need to update the bootloader for any of this to work, and that it cannot be updated unless I revert back to the 8MB/64Mbit chip.  If I remove the 16MB/128Mbit chip that I have soldered on now and replace it with the original chip, I am going to leave it the way it is and start this again on a fresh fuze board (not a NIB fuze obviously).  I have already ordered a used fuze (the one I operated on here was a bit beat-up to start with) to try this mod again in case the current one becomes unworkable.  The current board has taken a lot of hot air and I'm not sure it will take much more.

I've tried the enter button USB mode trick and it failed to work.  This guide (http://www.rockbox.org/wiki/SansaAMSUnbrick) suggests I can update the bootloader-patched OF with USB by connecting jumper pads on the board but I've had no success, "sudo fdisk -l" will just hang after it has listed all of my local drives and will only finish AFTER I've unplugged the fuze from USB, without listing a device number/address for it.  Do you have any other suggestions for how to change bootloaders on my current fuze before I put the 8MB ram chip back?  Once I put that 8MB chip back on, it's staying there.  I'll try the ram swap again on another fuze.

saratoga:
You might want to look into soldering a JTAG cable to your fuze.  That would let you not only update the bootloader without USB, but also let you manually flip bits in the memory controller.

sss:
http://www.rockbox.org/wiki/SansaAMSJTAG

I noted JTAG in the wiki but there are no pinouts for the sansa fuze (not v1 nor v2).

funman:
The problem is that the OF upgrade procedure uses the SDRAM.

The unbrick procedure will never work because the program is written in ROM, so I was suggesting that you use the normal upgrade procedure of the OF with mkamsboot.

If you could use JTAG it would be simpler. You "just" need to:

* Figure out the pinout for Fuze
* Be able to do micro soldering (the pins are really small)
Another option would be to unsolder the NAND flash and change the content yourself with a separate controller

sss:
The flash chips have finer lead spacing than the ram chips.  I really don't want to be exchanging those when I don't need to.

Without a way to determine the fuze JTAG pinout, JTAG isn't much good.  Supposing we knew which pads were JTAG pads, what would I need to solder?  Are you telling me I need to tap BGA joints from the ARM chip?  ???

If there is no way to uncover the JTAG pinout, then perhaps the best way would be to try the mod again with the other fuze (should be coming sooner or later), making sure that the bootloader fits in IRAM and works the first time around (or else I'll need to debrick it too).

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