Hi:

Unless your work is "Mission Critical" you will spend a lot more money for
ECC memory over non -ECC ram.  You may want to check and see if your board
can support it before you purchase it.

to Answer the "registered" question, a search by using www.askjeeves.com:
produced this site:  http://www.dalantech.com/ram-overview.shtml

and found this info:

Buffered refers to where the RAM contains a buffer to help the chipset with
the large electrical load for when a computer has a lot of memory, while
unbuffered lacks a buffer. They are two different types of modules, and are
not interchangeable as some even use different printed circuit boards
(PCBs). To determine if the RAM is buffered or not, check the leads next to
the first notch. If evenly spaced the RAM is buffered. If you attempt to
install the wrong type, the stick will not sit properly and be offset.

Registered RAM means that the RAM has a delay on information transferred to
the stick or module by one (1) clock cycle. This type of RAM is meant for
servers or workstations that serve data to multiple users to ensure the
quality of the data being served. Also note that unbuffered and registered
RAM is not interchangeable (See Table 1).

Table 1

                Buffered Unbuffered  Registered  Unregistered
Buffered        Yes       No            Yes             No
Unbuffered      No        Yes   No              Yes
Registered      Yes       No            Yes             No
Unregistered  No          Yes   No              Yes

What is parity, non-parity, ECC, and how are they related?

Non parity RAM is "regular" RAM - it has one (1) bit for every bit stored,
while parity adds a single bit to every eight (8) bits (1 Byte) for a very
basic form of error detection - that means that a 64 MB module of parity
RAM is actually 72 MB due to the extra bit added to every Byte.

ECC stands for "Error Checking and Correction". To figure out whether you
have ECC, parity, or non-parity RAM you need to count the number of chips
on the stick or module. If the total number of chips is divisible by 3,
then the RAM is ECC or parity. Otherwise, the stick or module is
non-parity. To differentiate if the RAM is ECC or parity, look at the part
numbers on the chips of the stick. If the part numbers are the same, then
you have ECC. Otherwise, you have parity. What is the difference between
parity and ECC? ECC and parity will both work in ECC mode, but ECC won't
work in parity (see Table 2) because although ECC adds a bit just like
parity for error checking, the bit isn't able to be individually accessed
like in parity. When building a system, keep in mind that ECC is said to
decrease your PC's performance by 2% as ECC is intended for servers or
workstations that are serving data that needs such precautions.

On a side note: ECC and non-ECC RAM can't be mixed.




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