I want to upgrade from the Flash/Ram from 8/64MB to 64/256 MB, I see that I need to remove the actual chips and install the new ones..
That is not the problem, the problem is, I need to be sure that the chips are compatible..and also the board has all the pins routed from the CPU to Flash/Ram..
Does the Chips need to have same frequency?I think so, due to the routing characteristics of the layers in the board..
Any one here have done that?
How can I later install the bootloader so that I can later do the "tftp install of openwrt"?
Does Î have to save first the contents of the old flash?
I am in the process of acquiring a ch341 flasher for that..
I would be immensely grateful to anyone that can guide me on this.
Many thanks in advance
Take a step back and reconsider if that's really what you're looking for:
mt7620 is a tad old, while increasing flash and RAM will help you, it won't make the device a runner
changing either of these will require you to (keep-) building OpenWrt from source with your custom patches to DTS and image recipes 'for all eternity', you will never be able to flash an unmodified firmware again
replacing the flash is relatively straight forward, but still pretty small. You need a good soldering iron for this (80++ EUR/ USD), a ~0.50-2.00 EUR flash chip (and your limit is likely to be 16 MB, not 32 or 64 MB, as anything above 16 MB needs to have the board having the necessary traces and resistors where they need to be for that) and a little practice
replacing the RAM is more intricate
you need to carefully check spec sheets for compatible modules
desoldering them without damaging the module is hard, so you probably want a new chip
on top of the good soldering iron, you will need a hot air soldering station
Maybe, just maybe, replacing the whole device is more sensible - and maybe it's even cheaper (unless you already own all the necessary components and soldering tools).
Replacing the chip(s) is relatively easy with the right heat gun. You just heat the chip until you can lift it off, clean the contacts of old solder with flux and a wick, add a lot of flux and the pads will form perfect bubbles of solder when solder is applied, set the chip on top and align, apply downward pressure and heat the chip until it melts the solder underneath.
The rest is what I was afraid to go into: the OpenWrt flash is expecting 8/64 and won't the partitions be set by the flash?
So I guess that is what you mean by "image recipes"?
But that takes the fun out of tinkering.
I do not think they know what they are getting into anyway; basic memory speed is just one area they should not have to ask about.
Flash partitioning and RAM size are hardcoded in the DTS, the image recipes and tplinksafeloader, all of these need adapting - forever.
The bootloader may- or may not need patching/ rebuilding, impossible to say from the outside.
I'd be with you, if we were talking about mt7621a and 'only' replacing the flash with a 16 MB chip - but mt7620a and the RAM are beyond what I'd be willing to do.
