Hello!
I run out of ram memory. Luci "Memory Total available" states 1-3%
So i thought why not to upgrade ram memory chip? Did anyone did this? Do any ddr chip for 256mb is compatible? does stated in datasheet memory speed matter? Any firmware upgrade needed?
I opened my router and found out that my chip is Zentel a3t1gf40cbf-gm. Some datasheets on other 256mb memory show that pinout is the same. Found couple chips from aliexpress for 3 euros.
It feels like any ddr3 in the same FBGA-96 packadge,same pinout, and same or grater frequency will do.
chips with 512mb memory have different data pins pinout (vss vdd we looks like same) i dont think that they fit
Share your thoughts about it.
(Also having thoughts change spi for 32 mb or nand, but need advice and programmer 
)
P.S. Also found that 2 capacitors in my router exploded (one is visible, green on the right), and replaced them.
If you have got too much time and are not afraid to turn your router into a brick, why not?
Do you have got access to the professional equipment you need to successfully replace a FBGA chip?
Yes? Lucky you...give it a try.
No? Don't expect to be successful without it.
What are you running on your router that uses so much RAM?
Ram usage:
Wireguard server, adblock service, i think they took most of it 
I dont have professional rework station, but i have a 500W projector with dimmer that can be used for down heating and soldering heat gun station 
Dont think that ordering and replacing chip take too much time (1-2 hours)
But i spent half of a day today serching info about compatibility, but found nothing useful.
Check out the datasheet of the SoC and check what kind of RAM or flash it expects, most values are usually given in ranges. As long as your new chip fits those values I don't see why it wouldn't work. As @elder_tinkerer already pointed out, it is very difficult to replace even with professional equipment. By all means, go for it, but don't expect it to be properly soldered on on the first try, or any try.
I hope this is a joke. If you're serious that this is your planned rework method, you should expect that you will damage your device (likely beyond repair).
Worked for gpu "repair", and other small soldering at home. I use k-type thermometer not to overheat thing. My soldering station heat gun is also calibrated. This is not a big chip, so not a big problem if i dont sucseed from the first time.
I am not professional anyway, just tinkering with electronics for fun and when i need something to try to repair.
Mt7621 soc datasheet:
16-bit DDR2/DDR3 up to 256/512 Mbytes memory interface
"The DDR3 SDRAM interface complies with 600 mhz timing requirements for standard ddr 3 sdram interface drivers sstl_15 drivers matching the EIA/JEDEC standard JESD79-3E (TBU)"
Dont really understand everything but said 600mhz ram in cpu datasheet. parameters of currently installed ram:
DDR3 1Gb 64Mx16 1.5V FBGA-96 MP HP = 1866 @CL13, GM = 1600 @CL11
So bigger frequency of chip doesnt seem to be an issue.
In theory 512mb ram could be installed if T3 and T7 are routed on the pcb.
Also as i understood ram config is hardware difined auto detect or eeprom?
Maybe someone already dissasembled these boards and know if T3 and T7 routed and if dram bootstrap is set to auto detect?
There're funnier ways to destroy a router...a hammer, an axe, or even thermite.
To try to resolder 1 or 2 broken GPU-to-board connections on a graphic card is completely different than to swap the whole chip.
Do you want any recommendations on new hardware before or after you destroyed the router beyond repair?
I am thinking about two options incase it dies: Old pc with 2 lan cards running openwrt, switch connected to second card and ap to switch. Or buying xiaomi AX3200 (openwrt firmware definitely flashed after)
I have soldering fan station with temperature control, not construction site heat gun. english is not my native language so sometimes i can be unclear
Another possible solution:
Get yourself a (used) RaspPi 3B+ or 4 and run your adblock service (and maybe even your WG server) on it.
Update: K4B4G1646E-BYK0 512 Megabite Chip ordered
raspberry pi price in my region about 50eur, and people dont care if its used, xiaomi ax3200 same 50euro new. so I think ax is better option
I did several router ram upgrades, mainly xiaomi/redmi:
-
Xiaomi 4A Gigabit v1/v2: 128 -> 512 MB
-
Redmi AC2100: 128 -> 512 MB
-
MiWiFi mini (MT7620): 128 -> 256 MB (DDR2)
-
ZTE e8820 v2: 64 -> 128 MB (DDR2, using miwifi mini's chip from above)
-
BOLT! Arion (PL-100): 128 -> 512 MB
What you'll need:
- A way to flash your router directly to the chip (like CH341A for the common SPI chip)
- A bootloader that can recognize and initialize your new RAM (like BREED or custom u-boot)
- Hot air station
- DDR2/DDR3 chip (must be the same package, like BGA-96 for DDR3 or BGA-84 for DDR2)
- Solder flux paste (the syringe ones)
- (optional) solder paste/balls, for the inevitable reball
- (optional) reball stencil, for the inevitable reball
This procedure is risky, ripped pads and bricked router is very very possible.
Not every chip is stable, if you want, you can hunt the specific chip names from Chinese forums before buying anything.
Before you proceed to change the RAM chip, you need to make sure you changed your bootloader first. The original bootloader cannot recognize different size chip.
OpenWrt should automatically detect your new RAM size and use it.
IMO, (almost) all mt7620 and mt7621 router can be upgraded (except the ones that integrated the RAM in the SoC), but they need at least the bootloader change.
Hello
Thanks for your reply! I understand bga soldering problems and previously ordeded stencils, 0,45mm lead ball (tin/lead paste just incase balls are bad quality). nc559 and rma223 flux i had before.
Chip model i ordered (K4B4G1646E-BYK0) must be samsung but this is aliexpress. Packadge is the same fbga-96, and i checked the timings and frequency be tha same as mine.
I have an ezoflash programmer that must work with 25 series spi, but only with desoldering chip, this also is not a problem.
The biggest problem is: could you please provide me info how to modify bootloader? I have the same router that is on your first picture Xiaomi 4a gigabit, mt7621 ver.1 eco3, flash is gigadevice is it makes any difference.
You can try using BREED for PBR-M1 and follow this guide to succesfully boot to openwrt using it (start from step 22).
I correctly understand that in both uboot and breed cases I have to flash .bin file via spi programmer? Because if I start breed from step 22, the breed should already be in the router.
And if I choose custom uboot from github, and flash with 512mb ram setting, before i change ram would it start (autodetect work)?
Also Led and reset gpio pins parameters would be great.
MTD Partition Table,Kernel Load Address need to be changed or they fit?
You can use mtd to flash bootloader, for example in stock firmware:
mtd -e Bootloader -r write breed-mt7621-pbr-m1.bin Bootloader
In OpenWrt, you need to install and activate kmod-mtd-rw first to be able to unlock the u-boot (Bootloader) partition.
Custom u-boot compilation did not sucseeded. (workflow ended with error that unabled to fetch python). Installed breed, same version that you provided. Your info helped me alot Thank You!
Do I have to know anything special about that now? Maybe i have to upgrade openwrt different ways with that bootloader? Or everithing will stay the same?
