Trouble with Asus SK8V MB with more than 2048M memory

[Maurice Hilarius]

Bryan J. Smith wrote:
> On Sat, 2006-04-08 at 10:41 +0300, Matti Pulkkinen wrote:
>   
>> I can't use more than 2048M of memory in my test machine. 
>> ..
>> I use two 2048M modules, Kingston's KVR266X72RC25/2G.
>>     
> ..
>> Has anybody been able to install Linux or FC5 x86-64 on that
>> motherboard with more than 2048M of memory?
>>     
>
> Yes, but I've always used four (4) 1GiB DIMMs to avoid lack of 2GiB DIMM
> support (and only getting half the memory).  I typically get 3.5-3.6GiB
> due to the hole sub-4GiB for memory mapped I/O.
>   
There are other issues as well:
The SK8V features the VIA K8T800 North Bridge
Many implementations of this chipset have issues with 4GB of RAM and the
BIOS location for add on devices such as PCI cards.

Reference some postings on this, for example:
http://forums.viaarena.com/messageview.aspx?catid=12&threadid=69763&enterthread=y

Further, I advise not going over 3GB with boards like this, in general,
as there is loss of memory performance.
Typical chipsets for single CPU such as this can only run RAM at full
speed (DDR400) IF there are no more than 6 ranks of memory chips.
Typical 1GB modules can only be had in a "2 rank" layout (64x8), and 2GB
are usually the same (128x4)
If you want to keep the ranks down you need to order  1GB modules using 
128 x 4 which are quite costly. Usually at about a 40% premium.

To go to all this trouble for 4GB is a bit of a waste, however, as you
are still going to be losing some of the addressing below 4GB due to the
BIOS ROMs occupying those addresses.
In general on a PC one can count on losing about 300MB of RAM address
space, so installing 4GB is a bit futile

I would recommend, instead:
A pair of 1GB, 64x8 (2 rank) modules
A pair of 512MB, 64x8 (1 rank) modules.
This achieves 3GB, accounts for 6 ranks, so memory speed stays full.
Costs no premium.

2GB modules are an awful lot of money, for the small difference you will
get here..
Especially since it guarantees you will be running your RAM at DDR333..


Unless you plan to overclock this I also suggest NOT wasting your time
with any of the so-called "faster" RAM, that is less than CAS3.
It is only needed for overclocking, and the premium should not be too
much. Most of the "Overclocking, low CAS, "premium" RAM one is offered
is at best "snake oil".

 For the cost of the "faster" RAM one can buy, it is usually possible to
go up one speed in the CPU model, or buy more RAM, so the "faster" RAM
is a bit silly, IMHO.





-- 

With our best regards,


Maurice W. Hilarius        Telephone: 01-780-456-9771
Hard Data Ltd.  FAX:       01-780-456-9772
11060 - 166 Avenue         email:maurice at harddata.com
Edmonton, AB, Canada       http://www.harddata.com/
   T5X 1Y3

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/amd64-list/attachments/20060408/d7a38203/attachment.htm>