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NVIDIA A01 Spin of MCP55P
The next generation NVIDIA core logic aims to be the company's most ambitious yet

NVIDIA has been quiet about core logic since nForce4 x16 was launched a few months ago, but the company is rapidly approaching on final silicon for the MCP55 family.  MCP55, as we reported previously, is the nForce4 successor dedicated to Socket AM2/S1 motherboards.  Our sources in Taiwan have just confirmed with us that MCP55 spin A02 is available to manufacturers and is already implemented on working motherboards.  The A01 spin has been floating around on engineering samples since January.  Traditionally, A02 and A03 spins end up in the market place on retail motherboards.

Unfortunately, MCP55 is a far cry from a revolutionary chipset.  According to NVIDIA roadmaps, it contains a different audio codec, dual Gigabit Ethernet PHYs and can use six SATA channels instead of four, but the core logic is still hampered by the fact that it takes two chipsets to control a 2x16 SLI setup.  The majority of games today cannot take complete advantage of 2x16 SLI yet, but adding two Northbridges to the motherboard to enable 2x16 seems like an incredible waste of money (particularly when the interconnect between the two bridges is only exactly enough for than the actual x16 PCIe bus, even though there are other devices on the controller). 

ATI's still unreleased Xpress 3200 (RD580) core logic can support 36 PCIe lanes on the Northbridge.  Recent roadmaps revealed that a stripped down version of RD580, RD550, will compete directly with MCP55P with 2x8 PCIe lanes rather than a full 2x16 for multiple GPU support.

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By KristopherKubicki on 2/27/2006 7:01:16 PM , Rating: 3
The NF4 X16 is composed of a CK804 and a C51 MCP. Both can be used as northbridges and both technically are. Whether or not they are designated as a south bridge or a north bridge is really not significant.

The interconnect between the two chips is a 2000MHz HT link, which is capable of 4GB/s in each direction. Several manufacturers actually limit the interconnect to 1000MHz for some reason, but that is a whole different issue. Regardless, if there was nothing else on the southbridge, the second PCIe x16 card could saturate the link between the two core logics... but NVIDIA also puts the SATA, PCI and Gigabit PHY on that bus as well. This is why I said the transport bus between the two chips is not all it could be.


By kilkennycat on 2/28/2006 2:19:45 PM , Rating: 2
Kris, thanks for improving the accuracy of the text in the article with regard to the bandwidth between the 2 chips in the nF4 X16 pair.

By kilkennycat on 2/28/2006 2:30:10 PM , Rating: 2
"....but adding two Northbridges to the motherboard to enable 2x16 seems like an incredible waste of money....."

The actual SLI chip-set counts are as follows:-

nF4 SLI X16 nF4 SLI ( X8 )
AMD 2 bridge chips 1 bridge chip
Intel 2 bridge chips 2 bridge chips

By Trevor311 on 3/1/2006 8:57:02 PM , Rating: 2
Ok, question then...I have an nForce 4 x16 system (Asus A8N32-SLI Deluxe) with 4 SATA drives (1 Raid-1 and 1 Raid-0) on the nvRaid chip, 2 7800GTX cards in SLI, and an SB X-Fi Fatal1ty card (PCI).

Would this interconnect bandwidth limitation be a possible cause for the X-Fi exhibiting static/crackling/hissing? (doesn't appear to happen when playing back MP3s, only when I'm playing WAV or playing games). There's a TON of users posting in the Creative forums about this problem, not all of them are using the same chipsets, etc., but many of them are using x16 mainboards with SLI graphics cards.

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