Is it possible to upgrade nand storage on router?

i had succesfullly upgrade my redmi ac2100 (MT7621a) from 128mb to 512mb
i want to ask, is it possible for me to upgrade the storage as well?
what is the maximum capacity of mt7621a? (both on ram and storage)

can i upgrade/replace the cpu as well? to mt7622 or s905x

If you're very, very, very good at soldering, you might be able to.

I'm not very, very, very good at soldering, so I wouldn't try.

Well done! That's a tricky operation.

Looking at the NAND flash driver for the 7621, I see only references to 16, 64, and 128MiB flash sizes. Nothing larger.

It's unfortunate, because the ac2100 doesn't have USB, so you can't easily use external storage.

I'm sorry, no. You would need a SoC that is pin compatible with the MT7621, and that doesn't exist. The MT7622, for example, is a completely different CPU (64-bit ARM) than the MT7621 (32-bit MIPS).

He clearly is, since he replaced the RAM.

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Indeed! I (foolishly) assumed the RAM would be a SODIMM or similar, and easier to swap out than a soldered NAND unit. So I stand corrected, and I salute the OP's soldering skills.

The solder equipment you will need to de-solder the old memory and at the same time make the PCB survive the removal operation and then the other solder equipment to solder the new IC will cost you 10 times more than the most expensive new and better router you can find on the market.

If you had the solder equipment required already you wouldn’t ask the question anyway.

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thanks but i think i'm not that good, i'm just following tutorials on ac2100 threads here, and some people already manage to do it...
unfortunately that thread is not that active anymore, so i think i can have some answers here...

i see, so cpu upgrading is not possible because of different architecture...

but i'm still curious about the nand upgrade...
i've do some research and find this chinese github page

he said he manage to upgrade MT7621S with 512mb ram and 1gb storage....
unfortunately the cpu model is different with my router (MT7621a), so i don't know whether its possible or not

i also look around the mt7621 datasheet and find this

is says nand largepage, max 8G bit.... does it mean i can handle 8GB nand?

buying new router will be my second choice, the old router will be lying around.... and my rouuter is still working...
i consider this as a hobby, but i just want to know what is possible and not possible, so i don't ended up buying chip that does not work with the router...

8G bit is 8 gigabits, which is 1 gigabyte.

Your device currently has 128MiB, which is 1 gigabit. This is actually good news, because it means your existing chip must be using the large page size. It's much more difficult to do this if you need to change the page size.

You will need to find a larger capacity flash chip that is pin compatible with the one you have. I can't find any reference for the actual NAND flash chip your device is using. Can you open it and take a photo? There also might be some data in the dmesg ring log. See if there are any entries there about the existing NAND flash.

here is my Nand flash chip, its ESMT F59L1G81MB

hopefully i can increase it, since i used 71% of my storage

According to this, this means it's a 3.3v 1Gi-bit (128MiB) 8-bit bus flash. Yours is in a TSOP48 (48 pin surface mount) form factor, which you will also need for your replacement. Those chips appear to come in 48 ball, and 63 ball, and 67 ball BGI form factors too, so don't get the wrong one.

First of all, get the data sheet for your chip.

Then look at F59L2G81xx, F59L4G81xx, and F59L8G81xx chips (2Gi bit, 4Gi bit, and 8Gi bit versions of your chip), check their data sheets to make sure they are pin compatible to yours. There appears to be several manufacturers, make sure you are getting something truly compatible. Also check the page sizes, block erase size, and ECC requirements to make sure they are also the same.

You should also get a flash programmer, as the flash chip will need to be programmed before you install it. There is likely some pre-boot code on your existing chip, and your device may not even think about booting without it. You will need to tweak OpenWrt with the new flash size for that device, and get it laid out in a nice format on the new chip with bootloader, config, kernel, and overlay sections before you install it. Look at the existing flash layout on it's OpenWrt device page. Then take a look at the files in openwrt/target/linux/ramips/, specifically openwrt/target/linux/ramips/image/ - you might get lucky and be able to just tweak the image size and have OpenWrt's build system do all the rest of that work for you.

I also wouldn't even attempt this without a USB UART to get console access.

Here is a writeup for someone who replaced the flash chip on a BPI-R3. This device is a completely different platform, but it should at least point you in the right direction on the issues you will have to address.

Good luck! I haven't tickled a device in this way for a very long time. The physical soldering is tricky enough work, but in your case it's likely the easiest part.

so, i need to find the chip that have 48 bga
but what i don't understand, does page size and block erase size will affect performance or compatibility issues? (instead of already been 48ball chip)

and, can i just clone the existing nand chip to my router to new one? (bigger size nand chip)

thanks for the link anyway, i will read it to have better understanding...

No, 48 TSOP

It's a compatibility issue. If you the page and block erase sizes are different you will have a lot more to do in OpenWrt to make it work.

The final UBI partition has to be resized if you clone it, but possibly yes.

thanks, i got a lot of useful information

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