Types of Ram - can someone explain please?

[jemmo]

I have been looking at the manual for my antique motherboard and it says it supports;

from 8MB to 512MB SDRAM,
1GB registered SDRAM, or
1GB EDO DRAM (available for 66MHz processors only).

SDRAM devices are supported in the form of Registered DIMMS only.

What is the difference in these types of RAM, and I assuming that 1GB of registered SDRAM will be faster to load programs than 512MB SDRAM?

Is there any downside to fitting registered SDRAM (whatever that is)?

[Gecko]

SDRAM (Synchronous DRAM)
A DRAM technology that uses a clock to synchronize signal input and output on a memory chip.
The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are "in synch."
The synchronization eliminates time delays and allows for fast consecutive read and write capability,
thereby increasing the overall performance of the computer.
SDRAM allows the CPU to access significantly faster than EDO memory because the system clock controls it.

There are two types of SDRAM module organizations, unbuffered (also known as unregistered)
and registered.

Registered SDRAM:
There are registers between the chipset and the memory, registers delay
memory information for one clock cycle to ensure all communication from the chipset is collected
by the clock edge, providing a controlled delay on heavily loaded memories.

Unregistered SDRAM:
This is where the chipset controller deals directly with the memory.
There is nothing between the chipset and the memory as they communicate with each other.