X58 and P55 platform bandwidth query

[Gazb]

Query about X58 and P55 platform bandwidth

Now I know that if you want to run sli/crossfire on the P55 you only get 2x 8x PCI-E operation (unless it has the NF200 chip) but how much bandwidth is left for the remaining PCI-E slots and the SATA controller?

The main reason I ask is I'm trying to decide between i7 920 and i5 750 setups, mainly for gaming however there will be some music creation/editing and I'd like to be able to use FRAPS to capture some gaming action aswell and then edit said recordings. Leaving cost aside which is negated when I want more than 4Gb of Ram on the P55 setup, I got thinking about running raid or adding a decent PCI-E SATA Raid controller.

This is where I found myself wondering how much bandwidth each platform actually has, as I'm pretty certain I read somewhere (think it was a preview of 6Gb/s SATA drives) that on the P55 motherboard it was actually becoming saturated due to lack of bandwidth.

Hopefully I got the gist of what I'm querying across.

 

[mmj_uk]

Looking at these two diagrams:

P55 vs X58

It looks to me like the two chipsets are pretty much the same aside from the P55 having less bandwidth in the primary PCI-E 16x graphics slots (and no tri-channel memory), both Southbridges are basically identical and are connected via a 2GB/s DMI link.

The AMD Southbridge in 790FX motherboards is connected by a 2GB/s PCI-E 4x link also.

 

[Gazb]

Looking at these two diagrams:

P55 vs X58

It looks to me like the two chipsets are pretty much the same aside from the P55 having less bandwidth in the primary PCI-E 16x graphics slots (and no tri-channel memory), both Southbridges are connected via a 2GB/s DMI link.

Someone correct me if I'm wrong.

Thanks, I didn't realise they both used a 2GB/s DMI link.

Though the plot does start to thicken when you check out the the SATA 6Gb/s article on Anandtech which takes about the newer P55A motherboards with SATA 6Gb/s and USB3.0.

Asus and Gigabyte took a different approach to implementing the Marvell 9123 chipset on their motherboards. Asus’s top of the line P7P55D Premium (a very good board by the way, full review coming shortly) features a PEX PLX8613 PCIe bridge chip that will convert four of the P55’s PCIe x1 lanes (250MB/s each) into two 500MB/s lanes. While still short of the maximum theoretical 600MB/s transfer speed of the SATA 6G specifications, it will provide more than enough burst bandwidth for the first generation 6G hard drives. The benefit is that the 6G capability is always on without affecting the other capabilities of the board and the same PLX chipset will be utilized for the upcoming USB 3.0 (NEC chipset) option on their upper-end boards.

Gigabyte’s implementation will be utilizing an x8 PCIe 2.0 from the Lynnfield processor that will obviously provide more than enough bandwidth but the drawback is that CF/SLI capabilities will be disabled as only a single x8 PCIe 2.0 lane will be available to the GPU. The benefit in this approach is that the SATA 6G switch is disabled/enabled in the BIOS by the user based upon need. Since an additional hardware chipset like Asus is utilizing is not required, it should result in a slightly lower board cost. Gigabyte informed us this week that all P55A-xxx boards will feature both SATA 6G and USB 3.0 capabilities. We will compare the performance of Gigabyte’s solution against Asus’ implementation shortly.

 

[mmj_uk]

Well if the Gigabyte board is using one of the Lynnfield's on-die PCI-E channels then it will be full speed and won't have any affect on any other add-in cards except you'll be limited to a single graphics card at 8X which is a few percent loss I think...

Maybe wait for the new X58 motherboards they will probaby have a much better implementation using the extra bandwidth supplied by the X58 Northbridge.

 

[Gazb]

Doesn't appear to be much info on when X58A motherboards will become available.