Buffers and registers are slightly different, however SDRAM that is not registered is referred to 'unbuffered' so confusion is inevitable. As a rule, SDRAM can be registered whereas older memory types (EDO, FP) may be buffered.
For this sort of question it's generally useful to look up the chipset datasheet
Unbuffered and Registered
SDRAM (Synchronous) DRAM
Support
So yes, the chipset supports it. But reading on you see that:
EDO, SDRAM and Registered SDRAM cannot be mixed within a system.
So no mixing.
If a
given row is populated with a registered SDRAM DIMM, an extra clock is inserted between the
read command the when the 82443BX samples read data.
So reads from a registered DIMM are one clock slower than from an unbuffered one. Registered SDRAM is not a performance option 😮
Finally, the chipset supports registered memory, but motherboard design and BIOS do not necessarily do so.
Asus' P2B-F manual for instance states:
Sockets are
available for 3.3Volt (power level) unbuffered Synchronous Dynamic Random Access Memory (SDRAM).
Similarly the Tyan Tsunami S1846:
The 168-pin DIMMs must be
of the 3.3V, unbuffered variety.
However Supermicro's P6DBS, P6DBE, P6DBU, P6SBU, P6SBS,
P6SBA and P6SBM Motherboards differ:
Maximum of 1 GB EDO at 66 MHz or 512 MB unbuffered 3.3V SDRAM,
or 1 GB registered SDRAM
So basically, just read the manual of your specific motherboard(s).