We're doing a project that uses about 150 DDR2 SODIMMs. Because we're using an FPGA, rather than a conventional motherboard chipset, the DDR2 controller IP demands we have to burn the DIMM timing into the FPGA when synthesising it, rather than reading the EEPROM at runtime. The FPGA DDR2 memory system is a lot less bulletproof than the average motherboard, so it needs to be heavily tested with a specific DIMM.
That means sourcing memory for this thing is a bit of a headache, because supply of DIMMs tends to change from time to time. For cost reasons we're buying from standard PC parts suppliers, not the DRAM vendors' distributor themselves (suspect this won't be high enough volume to make sense wholesale).
Part of the fix for this is buying a particular part number of DIMM. But I'm particularly worried about things like the DRAM part or PCB changing, without the DIMM part number changing. Witness all the wireless routers with the same model number but even a completely different CPU arch inside.
One way is to buy them all at once, and do exhaustive testing on examples. But it's a bit awkward to persuade a supplier to take them all back if it doesn't work out.
An alternative is to assume the same part number means identical components, perhaps between a sampling phase and a bulk purchase phase. Is this likely to be true? Or does revving still happen in this sector?
Has anyone experience of using such commodity items in an embedded project?