Re: New Motherboards ECC memory and PCI-E issues

jimomuraNOSPAM@xxxxxxxxxxx writes:
I have pretty much decided on a couple of motherboards, but there
are a couple of issues I would like to find out more about:

1. I have ECC memory on one of my current computers, and I had
hoped to have ECC on my next motherboard. I noticed that DDR2
memory with ECC is "non-buffered".

You can also get registered and fully-buffered ECC memory. Note that
every board can only handle one of the three sorts of RAM:
unregistered (unbuffered, e.g., 5300U), registered (e.g., 5300R) or
fully-buffered RAM (e.g., 5300F); so make sure you buy the right sort.

I do not understand how you
can have ECC without buffering. Can someone explain this?

This is not about the buffering that the memory controller performs.

The difference between unregistered and registered RAM is that
registered RAM has additional driver chips on the DIMMs that allow to
have more chips on the DIMM without increasing the load on the lines
to the DIMM. AFAIK the address (and maybe the chip select) lines are
driven in that way, the data lines are still connected directly.

In fully-buffered DIMMs all the signals pass through an interface chip
that translates between the FB-DIMM protocol on the board and the
regular DDR2 protocol on the DIMM. Also, while with unregistered and
registered DIMMs the memory controller talks to all DIMMs in a
channel, with FB-DIMMs the memory controller talks to the first DIMM,
the first DIMM to the second etc. FB-DIMMs consume significantly more
power and need good cooling.

2. PCI-E has been around for a while in 1X, 8X and 16X
slots (an 8X slot being a 16X physical slot but 8X support).
The 4X slots are, from what I gather, actually "new". Looking
at the PCI-E spec, 1X is actually pretty fast. But it
seems to me that there is sort of a trend to the new 4X
slot. It is unclear whether there is any physical reason
why a 16X slot cannot handle a 4X card. It appears to
me that this is a BIOS issue. So far I have not read
anything that indicates that a 16X slot can support a 4X
card. Does anyone know about this? Is it just presumed
that a 16X slot will handle all the smaller cards?

AKAIK yes, but I don't have experience with that.

- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton@xxxxxxxxxxxxxxxxxxxxxxxxxx Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html
.

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