ASUS RT-AC66U Will not boot but CFE is OK.

[quanttrom]

I got my hands on a used Asus RT-AC66U router and I have been trying to resurrect it. I have no idea what was done to it before but when I got it, it would go into Recovery Mode (slow blinking power LED) by itself and stay there.


1) My first step was to use the ASUS recovery utility. It uploaded the firmware successfully but it would still not boot properly (stuck in recovery mode). After that I connected the serial port to see what the output is during bootup. This is after trying to flash with ASUS recovery utility.

CFE version 6.30.39.16 (r331229) based on BBP 1.0.37 for BCM947XX (32bit,SP,LE)
Build Date: Fri Jun  1 10:34:33 CST 2012 (defjovi@F13)
Copyright (C) 2000-2008 Broadcom Corporation.

Init Arena
Init Devs.
Boot partition size = 262144(0x40000)
Found an ST compatible serial flash with 32 64KB blocks; total size 2MB
Found a Samsung NAND flash with 2048B pages or 128KB blocks; total size 128MB
bcm_robo_enable_switch: EEE is disabled
et0: Broadcom BCM47XX 10/100/1000 Mbps Ethernet Controller 6.30.39.16 (r331229)
CPU type 0x19749: 600MHz
Tot mem: 131072 KBytes

CFE mem:    0x80700000 - 0x8084E720 (1369888)
Data:       0x807384B0 - 0x8073B750 (12960)
BSS:        0x8073B750 - 0x8074C720 (69584)
Heap:       0x8074C720 - 0x8084C720 (1048576)
Stack:      0x8084C720 - 0x8084E720 (8192)
Text:       0x80700000 - 0x807384A8 (230568)

Device eth0:  hwaddr 30-85-A9-<REDACTED>, ipaddr 192.168.1.1, mask 255.255.255.0
        gateway not set, nameserver not set
Null Rescue Flag.
Hello!! Enter Rescue Mode: (by Force)

Reading :: TFTP Server.
Failed.: Timeout occured
Reading :: TFTP Server.
Failed.: Interrupted
CFE> 
CFE> 
CFE>

2) I tried clearing the nvram; That has not helped.
3) I tried loading the oldest & newest firmwares from ASUS as well as variety of 3rd party firmwares. They would load fine but no success.

4) I was able to get it to partially boot (by interrupting the image loading process mid-load by pure luck. The image when I booted was not full and was not really usable
Snippet:

CFE version 6.30.39.16 (r331229) based on BBP 1.0.37 for BCM947XX (32bit,SP,LE)
Build Date: Fri Jul 20 15:25:26 CST 2012 (defjovi@F13)
Copyright (C) 2000-2008 Broadcom Corporation.

Init Arena
Init Devs.
Boot partition size = 262144(0x40000)
Found an ST compatible serial flash with 32 64KB blocks; total size 2MB
Found a Samsung NAND flash with 2048B pages or 128KB blocks; total size 128MB
bcm_robo_enable_switch: EEE is disabled
et0: Broadcom BCM47XX 10/100/1000 Mbps Ethernet Controller 6.30.39.16 (r331229)
CPU type 0x19749: 600MHz
Tot mem: 131072 KBytes

CFE mem:    0x80700000 - 0x8084E7A0 (1370016)
Data:       0x80738530 - 0x8073B7D0 (12960)
BSS:        0x8073B7D0 - 0x8074C7A0 (69584)
Heap:       0x8074C7A0 - 0x8084C7A0 (1048576)
Stack:      0x8084C7A0 - 0x8084E7A0 (8192)
Text:       0x80700000 - 0x80738528 (230696)

Device eth0:  hwaddr 30-85-A9-<REDACTED>, ipaddr 192.168.1.1, mask 255.255.255.0
        gateway not set, nameserver not set
Null Rescue Flag.
Hello!! Enter Rescue Mode: (by Force)

Reading :: TFTP Server.
Failed.: Timeout occured
Reading :: TFTP Server.
Device eth0:  hwaddr 30-85-A9-<REDACTED>, ipaddr 192.168.1.49, mask 255.255.255.0
        gateway 192.168.1.49, nameserver not set
Failed.: Timeout occured
Reading :: TFTP Server.
break! no netctx or timer expired ! 
break! no netctx or timer expired ! 
break!! reach max retry!!
Failed.: I/O error
Loader:raw Filesys:raw Dev:nflash0.os File: Options:(null)
Loading: ...... 3392356 bytes read
Entry at 0x80001000
Closing network.
Starting program at 0x80001000
start_kernel
Linux version 2.6.22.19 (root@asus) (gcc version 4.2.3) #1 Wed Aug 31 04:03:52 CST 2016
CPU revision is: 00019749
Found an ST compatible serial flash with 32 64KB blocks; total size 2MB
Determined physical RAM map:
 memory: 07fff000 @ 00000000 (usable)
 memory: 08000000 @ 87fff000 (usable)

5) I have been able to flash the CFE with a different CFE. Worked fine:

CFE version 6.30.39.29 (r338244) based on BBP 1.0.37 for BCM947XX (32bit,SP,LE)
Build Date: ä¸ 10æ 15 10:41:41 CST 2012 (yau@wireless-pub2)

Not entirely sure about the garbled character but it appears that other users with the same CFE have them.


Suspicions:
1) Stuck reset button? I measured out the button with a multimeter it seems to be working but maybe there is a hardware fault somewhere else.
What makes this line appear? Specifically "By Force" ?
I tried to find the source code for CFE but I suspect I wasn't looking hard enough.

Hello!! Enter Rescue Mode: (by Force)

2) Is it possible there is a bad block in the flash? Does the CFE Flash programming process check for that during firmware flash?

 

[Pierino]

He took the cfe' from here. Same posts on the dd-wrt forum.

 

[quanttrom]

I found this ...same "Hello!! Enter Rescue Mode: (by Force)" but different model
http://www.snbforums.com/threads/asus-rt-ac5300-bricked-what-to-do.35718/

with a video:
http://www.snbforums.com/threads/asus-rt-ac5300-bricked-what-to-do.35718/#post-290783

where did you grab your cfe?
http://www.snbforums.com/threads/asus-routers-cfe-dumps-collection.17793/

Maybe that could help you.Found all this on that forum
Welcome to SNB

Thank you for the warm welcome

I have gone through the recovery procedure as described in the video without much luck. It goes through the recovery process and still fails in Recovery Mode (slow blinking Power LED and CFE active; does not boot image)

He took the cfe' from here. Same posts on the dd-wrt forum.

Hopefully I don't upset anyone by multi-forum posting.

Yeah, this is where I got the CFE from.


I'll try an older CFE just for testing purposes and see if I get different results.