Fast, reliable techniques to repair memory modules with the RAMCHECK^® LX memory tester

The RAMCHECK LX memory tester is a powerful tool for repairing defective DIMM and SODIMM modules by pinpointing the defect and identifying the defective chip. Of course, the first thing you need to do is test the suspect module to confirm that it is faulty. This takes just a few seconds with RAMCHECK LX.

RAMCHECK LX will quickly identify the module's speed, size and type, and give a pass/fail message. RAMCHECK LX error messages also generally identify the relevant pins (circuit connections to the test socket) of the module being tested which are associated with the problem. It is designed to provide you with explicit error data to enable you to identify the defective component(s) on the module.

RAMCHECK LX DETAILED ERROR MESSAGES RAMCHECK LX reports data bits error in each rank explicitly, using two lines. The first line is the "byte" view, indicating errors within byte 1 to byte 8 for an x64 module. You can scroll left or right, as the second line shows the individual bad bits within the bytes highlighted in the first line. In this example, DQ31 of RANK 2 is bad.     Use F3/F4 to get more detailed error information The first press of button F4 replaces the module size speed info in the bottom line with the explicit DQ error (DQ31 in this example). It also indicates the module pin number which is connected to this DQ line. As you will see below, knowing the DQxx error tells you which chip is bad!  Pressing F3 returns to the previous screen, an additional press of F4 drills down into more information. Here it tells you the address where the error was detected.  Press F4 again to see the Row/Column component of the address at which the error was detected.  Press F4 again to see the hexadecimal error in a 64 bit double word.  You can also see which test type found the current error. In this example, the error was found by an array type test that scans the memory array.   Here it shows the data in the S control lines. The S control lines include four lines, S[3],S[2], S[1] and S[0], each controlling one of the module's ranks. A module may have one to four ranks, marked RANK1, RANK2, RANK3, and RANK4. Ranks are strictly used in order, so that a two-rank module must use RANK 1 and RANK2 (never RANK3 or RANK4). In this example, S=2 means that S[3]=0, S[2]=0 S[1]=1 and S[0]=0, indicating RANK2. The B2/0 indicates RANK2 with bank address BA=000. In another example of a four-rank module, a message like "S=4 B3/5" is interpreted as follows: "S=4" means S[3]=0, S[2]=1 S[1]=0 and S[0]=0, indicating RANK3. "B3/5" indicates RANK3 with bank address BA=101.

When RAMCHECK LX reports a data bit error, it tells you which DQ bit/s are bad and it also identifies the relevant pins (circuit connections to the test socket) of the module which are associated with the bad bits. You can remove the module from the socket and review the Test Log of the last memory test by pressing F4 during Standby. Easier still, use the RAMCHECK PC interface to identify faults (see below).

Spotting the Defective Memory Chip

Every memory module has chips that are arranged from left to right (when you look at rank 1) in accordance with the bits (each bit has a DQ number) of the module. RAMCHECK LX data errors clearly identify the DQ bit/s which are bad and it tells you which chips are being used. You can easily identify the bad chip from the RAMCHECK LX data errors as follows.

The most popular modules (regardless of size and DDR1/2/3 type) use individual chips with x8 data width. Therefore, x64 module uses 8 such chips per rank and ECC (x72) uses 9 chips. The first chip on the left always connects to DQ0-7. The second chip connects to DQ8-15, the third chip from the left connects to DQ16-23, and so forth. The ECC chip (for DQ64-71), if available, is placed in the middle of the module as the 5th chip, as shown in the following drawing.

For example, if RAMCHECK LX reports the error DQ17 bad, you know it is the third chip (DQ16-23)  from the left. If you test a dual rank module (one that has chips in both sides), you need to follow the RANK number reported by RAMCHECK LX. If it is RANK 2, you need to turn the module over and follow the chips in a reversed order - DQ0-7 of RANK 2 will be the first chip on the right side when you look at the back side of the module.

Similarly, an x64 data width module (regardless of size) that uses x16 data width individual chips, has 4 chips per rank. The first chip on the left always connects to DQ0-15. The second chip connects to DQ16-31, the third chip from the left connects to DQ32-47, and so forth, as shown in the following drawing. So if for example RAMCHECK LX reports the error DQ30 bad in RANK 1, you know it is the second chip.

If RAMCHECK reports DQ30 in RANK 2, the bad chip will be the second from the right when you look at the back side of the module, as shown here