Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <g3Sge.749755$w62.333443@bgtnsc05-news.ops.worldnet.att.net>,
bosco335 <bosco335@att.net> wrote:
> I'm a newbie at building up systems.... Have an Asus A8N-E board. The
> manual says due to CPU limitation the board doesn't support
> "double-sided x 16" DIMM modules. Does the "16" refer to the number of
> chips on the module? I bought a couple of sticks of Mushkin basic green
> and it's double-sided with 16 chips on it. Do I have to go out and buy a
> different brand? I haven't been able to find any DDR400 that isn't DS
> with 16 chips on it.
The "x16" part refers to the width of the data bus interface
on each memory chip. A "side" or "rank" of memory is 64 bits wide
in total. If you have memory chips with 16 bit data busses
on them, it takes four of those chips to make a "side" of RAM.
So, Asus is saying, if the DIMM has four chips on one side,
and four chips on the other side, it is not supported. (This
is something I cannot verify in AMD's documentation, so I
cannot tell you if it is related to a particular stepping of
S939 processor or not.)
You can use double sided memory. Most commodity 512MB DIMMs
have a total of 16 chips, 8 per side. Each chip would be
32Mx8 bits of memory.
It is also possible to build 512MB DIMMs single sided, in
which case 8 chips of size 64Mx8 bits each would be used.
I'm not aware of any 512MB DIMMs fitting Asus description
above, so you should be able to safely buy 512MB DIMMs
without worrying about that "x16" statement.
The illegal ones that come to mind based on the Asus rule:
128megabit memory chip = 8Mx16 or 16Mx8 type chips
(16) 16Mx8 would make a double sided 256MB DIMM
(8) 16Mx8 would make a single sided 128MB DIMM
(8) 8Mx16 would make a double sided 128MB DIMM
You can make a single sided 256MB DIMM with (8) 32Mx8 chips.
Basically just a half populated 512MB DIMM. That would be
OK with respect to the Asus rule.
So, let's see what the OK list would look like:
A 256MB single sided (8) 32MX8 would be OK.
A 512MB single sided (8) 64Mx8 would be OK (and expensive)
A 512MB double sided (16) 32Mx8 would be OK (and cheap)
A 1GB double sided (16) 64Mx8 would be OK.
You don't have too much to worry about. If you want to
buy 1GB modules, they require extra care when you buy them,
due to the prevalence of "stacked" RAM in the generic
market. If buying 1GB modules, buy them from a reputable
supplier like Crucial, Kingston, Corsair Micro and so on.
Many of the products listed on Pricewatch will be the
bad stuff (a low price is a dead giveaway for 1GB stacked
RAM). This is not a motherboard issue, but a RAM issue.
Stacked RAM are not JEDEC approved, and there is no good
reason for these to exist in the market. (Stacked RAM
are fine on registered memory modules, the kind used on
servers. Unbuffered stacked RAM is a no-no.)
Buying 2x512MB would be a worry free purchase.
If you are planning on buying four DIMMs, to fill the
board up, be aware that there have been reports on other
motherboards, of half the RAM not being recognized, if all
the RAM are not exactly the same DIMMs. If you had two CAS2
DIMMs and two CAS3 DIMMs, there is a chance that one of
the pairs of DIMMs would be ignored. This is a BIOS bug,
so should eventually get fixed. It is a matter of the
BIOS figuring out which DIMM is the slowest, and using
the info from that DIMM when setting up the memory
controller.
Paul
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