Hello, I recently bought a used SG135 rev.1 which has AVR54 bug (I found out about this bug after I buy it).
For others vendors I found a possible fix, but not for Sophos.
There are two (as far as I know) fixes:
1. Replace a atom c2xxx with C0 revision
2. external pull-up resistor (18.2k to 10k), from LPC_CLKOUT0 or LPC_CLKOUT1, tied to 3.3V
Did someone tried to fix this bug? (I use home license, so I don't have any agreement with Sophos).
Ahoj Robert and welcome to the UTM Community!
I haven't been inside an SG 135, are you telling us that the Atom processor cannot be replaced?
Cheers - Bob
Hello BAlfons, I didn't opened yet, but generally they are soldered to mainboard, so replacement is very, very hard.
I have the same issue. Anyone an Idea where to catch those Pins on the Board?
Do you have any picture of mainboard??? Can you share ???
yes, sure! Here they are (if you need more or more detailed ares let me know):
It would be great if there was a simple pullup to bring it back to life, but without schematics or layouts to hard for me.
I agree with you, without scheme wil be hard.
Hi Sophos Community,
is there any any hardware engineer from Sophos with access to schematics or layouts on board who could help? Any hint regarding the LPC_CLOCK_OUT pins would be highly appreciated.
Well I think you will not get an answer you hoped for. Intel has NDA with Sophos and so, they can't talk about it.
More about error:
According to this document LPC_CLKOUT0 is GPIOS26 or AG51 pin. But for LPC_CLKOUT1 is note that Intel has not validated this mode.
So for now look on mainboard, maybe are there some marks about this pins.
Found this document and location of AG51 is visible in table 35-6 (Sheet 2 of 6). For ball out look at the table 35-3. Has someone try to remove C2000 processor from board?
The only thing we need is now line from mainboard (bottom of cpu)!
It would be very nice to know which resistor have to be replaced exactelly....and I think this would be easier than replacing the whole cpu ;)
You don't replace a resistor you just add a pull-up to right line/resistor (CLK line from CPU which is output doesn't works anymore).
I cannot tell you on which resistor you add an external pull up (my sg135 still works). But you can try your self.
What will I do when my die, I will short all resistor on the left top side (look on the picture) with resistor tied to 3.3V. When I find a right place it should power on / boot (I think you must press power on button).
Having also an SG135 with defective Atom C2000, I stumbled upon the Nuvoton I/O Chip on the back of the mainboard, which should be connected to the LPC bus.
Maybe this is connected to the LPC_CLKOUT in some way, but i did not find anything confirming this. Could be a possible way for a DIY fix.
The datasheet mentions pin 15 as a Clock-Input for the LPC interface - just guessing...