[coreboot] seeking AMD 990FX / SB950 documentation

[Mark Nelson]

> On 18/07/12 17:04, Mark Nelson wrote:
>>> > Would someone please point out where I can get documentation on the
>>> AMD 990FX /
>>> > SB950 north and south bridges? The 800 series stuff is at
>>> support.amd.com, but
>>> > not these.
>>>
>>> Hi
>>>
>>>
>>> Yes I have same question, but maybe AMD folks here could sched some
>>> light on documentation release plan.
>>>
>>
>> I believe the 990FX and the SB950 are essentially the same thing as the
>> 890FX and the SB850 - the same silicon. AMD just transitioned to the 900
>> series numbering to easily allow consumers to tell whether a motherboard
>> has an AM3+ or an AM2 socket on there, and so whether it supports their
>> Bulldozer family of CPUs or not.
>>
>>  From the Tech Report:
>> "Led by the 990FX, this core-logic family is new in name only. The 990FX
>> consists of the same north- and south-bridge components as its 890FX
>> predecessor, and those chips continue to be manufactured by TSMC using a
>> 65-nm fabrication process."
>>
>>  From tom's hardware:
>> "The 990FX chipset employs the same silicon as 890FX.
>> ...
>> According to AMD, it’s incrementing the platform name to clarify
>> compatibility with Bulldozer-based processors. When you see a board that
>> centers on 990FX, the company wants you to know that its upcoming AM3+
>> CPUs are drop-in-compatible (again, 990FX-based boards will also take
>> existing AM3 chips)."
>>
>>  From Hardware Secrets:
>> "The AMD 990FX chipset is basically an AMD 890FX chipset with a new
>> name, but supporting the higher HyperTransport 3.0 speeds that weren’t
>> used before and that will be supported by the “Bulldozer” processors.
>> The AMD 990FX chipset is targeted to the new socket AM3+ platform, while
>> the 890FX chipset is targeted to the socket AM3 platform. This way, AMD
>> is providing an easy way to identify the platform through the chipset
>> name. Socket AM3+ motherboards support the forthcoming AMD CPUs based on
>> the new “Bulldozer” architecture. So, even though the chipset is
>> basically the same, 890FX motherboards won’t support this new generation
>> of AMD processors."
>>
>> Hope that helps!
>> Mark
>
> There must be something new about the 990FX because there's support in there for nVidia SLI. Earlier chipsets don't do SLI. Look here: http://blogs.nvidia.com/2011/04/you-asked-for-it-you-got-it-sli-for-amd/
>

Actually no, SLI support isn't anything to do with the actual chipset 
hardware (provided the chipset has the required number of PCI Express 
lanes and physical slots of course ;) ).

SLI certification (and so SLI support) is nVidia's way of controlling 
which platforms can run their GPUs in SLI mode (and making money out of 
it all of course). Board makers that want SLI support pay the 
appropriate licensing fees to nVidia (and submit their board models to 
nVidia for qualification) and they then receive a special key that they 
embed in their BIOSs which nVidia's drivers look for before enabling SLI.

You can read about this here (the article comes from when nVidia first 
supported SLI on Intel's X58 (Intel's first chipset to receive SLI 
support), but the method is the same):
http://techreport.com/discussions.x/15405

"Motherboard makers who wish to have their X58 boards certified for SLI 
will have to submit their products for testing in Nvidia's Santa Clara 
certification lab, and those boards must pass basic testing for 
functionality, slot placement, and the like.
...
Once a board is certified, Nvidia will provide the board maker with an 
approval key (called a "cookie") that it must embed in the system BIOS. 
The combination of this approval key and an X58 chipset will then unlock 
SLI support in Nvidia's ForceWare driver software."

The 990FX was just the first series of AMD's chipsets that nVidia 
allowed motherboard manufacturers to have SLI support for (prior to that 
their stance was, if you want SLI with an AMD CPU, we support that, via 
our nForce 980a chipset; but once they effectively stopped producing 
chipsets they had little choice but to allow board makers to certify 
their 990FX boards for SLI use, or to close themselves out of the 
high-end AMD desktop market in terms of SLI sales).

It's also not a given that just because a board is built around the 
990FX chipset it will support SLI, as it relies on the board having the 
"enable-SLI key" in the BIOS. Take Sapphire's Pure Black 990FX board for 
example - it doesn't support SLI even though it has a 990FX chipset, 
apparently because NVIDIA is restricting AMD platform SLI licences to 
only those motherboard vendors who already had them for the Intel platform:
http://www.techpowerup.com/146605/Sapphire-Pure-Black-990FX-N-is-Purely-for-CrossFire.html

There were enthusiasts out there who used SLI on their 890FX boards, it 
just required modified nVidia drivers, so that they enable SLI even on 
boards that don't have the key in the BIOS or a sanctioned chipset (this 
is what ULi did with a little utility to enable SLI on their chipsets 
(eg: M1697)).

So, with the 890FX docs, we should have everything we need for 990FX 
support.

Mark.