If your motherboard supports buffered sdram memory can you substitute unbuffered sdram modules?

Answer 1

Ive just been studying about all the forms of SDRAM etc, and when it came to buffered/registered DRAM I found out that normal PC's usually have upto 4 slots for SDRAM, any more gives producers of motherboards lots of electrical problems. So to solve the problem of systems that require maybe 6, 8 slots, they require special DRAM, such as buffered/registered SDRAM. This SDRAM has a special buffering chip on the address bus added to it to work as an intermediary between SDRAM & North Bridge. To take advantage of buffered SDRAM, the motherboard and brige must be able to support SDRAM. Slots requiring buffered DIMMs are keyed differently then those requiring unbuffered DIMMS so it will be physically not possible to install these DIMMs into the slots short of shaving the key. Electrically, possibly, but you have to remember that the register drives the addressing unit on the DIMM and the bridge will likely not be designed to accomidate the drain required to directly drive the memory chips on the address bus and as such may cause instability if it works at all. In addition there is a single clockcycle delay from when the address is written to the registers to when the address is propigated to the memory, in such timing errors could arrise from a bridge expecting that delay.

- you cannot use unbuffered SDRAM on a motherboard that supports buffered memory, because the notches on buffered DIMMS are in different positions than for unbuffered DIMMS.