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I have some difficult to find CPU from a board. First I though that CPU/SOC was this one :

enter image description here

All I know (about CPU) is that's an ARM core little-endian (because I begin reverse firmware in IDA) but I lack of information on it. The hardware is a 8 years old GPS with 800x480 tft.

According to Igor link document from Samsung, codification of K4X2G303PC - XGC6 means :

K : Memory

4 : DRAM

X : Mobile DDR SDRAM

2G : 2G, 8K/64ms (Density,Refresh)

30 : x32 (2CS, 2CKE) (Organization)

3 : 4Bank

P : LVTTL, 1.8V, 1.8V (Interface, VDD, VDDQ)

C (Generation)

X : POP (Lead-Free, DDP, Halogen-Free)

G : Extended, Low, PASR & TCSR (Temp, Power)

C6 : 6ns@CL3 (Speed)

Here is the whole board (warning EMMC is unsolded) enter image description here enter image description here

Here same hard, but component is another reference from Micron Technology (picture is 180° rotated)

enter image description here

And the backside

enter image description here

X16V554IL is quad UART (https://www.exar.com/content/document.ashx?id=505) I checked GND pinout it is corresponding

So if Samsung K4x2G303PC is not SOC/CPU where is SOC/CPU ?

Why is there a Crystal near K4x2G303PC ? (The other Crytal is for XR16V) Can Latticle CPLD LC4064 have an arm software core ?

REgards ;)

  • 1
    Please could you add a picture of the whole board ? – Ian Cook May 6 '17 at 4:43
  • Yes, I updated it – user2296435 May 6 '17 at 11:38
  • 1
    could it be that the CPU is somewhere else? what is this board from? – Igor Skochinsky May 6 '17 at 18:37
  • What are the two ICs between the Samsung RAM and the EMMC ? – Ian Cook May 11 '17 at 17:57
  • I also try to understand which CPU is being used there. Hard to find out, and I drilled down a little bit in a firmware bin file I have. If I am correct, the hex base address for the firmware running on that specific device ( a specific GPS device with a nice sunlight visible screen) is 0x80200000 , and indeed it is a little indian 32 bits arm code. There is a primary boot code also loaded at 0x80100000, and from the web surfing I made, that is to initialize among others the RAM. The entry point is not 100% easy to locate in the firmware bin file, and I am at that stage. I will now start to lo – hobi Sep 5 '18 at 10:44
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On this photo you can see there are two "layers" in this chip separated by a matrix of solder balls. This is package on package — a method used to save board space. The actual processor is hidden under the RAM chip.

Look at Raspberry Pi Zero — you won't find SoC there either! The chip there has Elpida label, which is a RAM manufacturer, and the SoC itself is under there.

  • This is it ! Amazing ! I didn't know. Knowing this I found this video : pop video at 1:45 min we can see approximately the same reference memory ( IBAI8 D9LFW <=> IBAI8 D9LBZ from Micro) and under the cpu chip... – user2296435 May 23 '17 at 6:57
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Are you sure it's a SoC and that is the IC the firmware came from? Results on Google suggest that is a DRAM chip. Looking at Samsung part numbers show that most of the memory chips (mobile and otherwise) seem to start with K as well.

  • 1
    Yes, it's consistent with the part numbers of their 2GB Mobile DDR SDRAM chips. I haven't found this specific one but other very similar parts seem quite common. e.g. K4X2G323PC or K4X4G303PC – Ian Cook May 6 '17 at 5:37
  • Yes THANKS, I think your are right. I find other reference for same hard (Micron Technologie) : IBAI8 on picture... They provide only DRAM, EMMC, NAND Flash but no CPU. So, it could be no SOC but just an Arm CPU ? Where is the Arm CPU ? Is it component reference XR16V ??? – user2296435 May 6 '17 at 10:03
  • Meanwhile, I think that X16V554 is quad UART (exar.com/content/document.ashx?id=505). SO I don't understand where is CPU ? – user2296435 May 6 '17 at 11:21
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You can use Samsung DRAM part number decoder to find out the exact specs of this DRAM chip.

So no, this is not the CPU, it must be somewhere else.

  • This is done. I updated description of subject with it. It seem this is just a DRAM. If thisis the case I don't understand why there is a crytal near it and where is cpu ? – user2296435 May 8 '17 at 16:49
  • good question, but I guess we need someone experienced in hardware to answer it. Maybe try to figure out JTAG, the chain scan might give the device IDs and from that some hints about the CPU. – Igor Skochinsky May 8 '17 at 16:58
  • another possibility could be to try tracing pins of DRAM and/or eMMC to see where they connect to. – Igor Skochinsky May 8 '17 at 17:00
  • I have tryed open-ocd on pins that seems JTAG header with no result. I will try a JTAG finder later. Perhaps il will unsolder chipset. But for now this is a mystery – user2296435 May 8 '17 at 19:01

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