Via KT-600

[funky-d-munky]

Fair enough.
Thanx.
funky

[Dr Mordrid]

Originally posted by Chrono_Wanderer
hmm... so the PCI issue actually refers to the issue between the southbridge and the northbridge?

so what about the intel and AMD chipsets? any info for those?

thx in advance

Cheers,

Ron

Both are issues with the VIA's. The interlink is slower than SiS and NForce2's AND the PCI burst is screwed as noted by TecChannel.de. Double whammy.

AMD runs between the SiS and nForce2.

Intel's Hub Link bandwidth is listed as only 266 MB/s, but their archetecture is more efficient plus the memory bandwidth is higher, so they end up a bit faster than the AthlonXP chipsets in pushing bits overall. In practice this lets RAID's capable of saturating the PCI bus run at about 115 MB/s on an Intel vs. 90-110 MB/s for nForce2/AMD/SiS and 60-80 MB/s for VIA.

Dr. Mordrid

[Chrono_Wanderer]

ic. thx for the reply doc

So that's why all you RT people like SiS so much...

Its a cheap solution and offers best interconnection architecture b/t the bridges.

oh yea... about the memory bandwidth for Intel chipsets... are AMD K8 platforms gonna have a huge advantage then? because of hypertransport...

and if that's correct VIA K8 may actually do "ok" (dispite the fact that the first dumping of video bits between through PCI bus is slow and stuff...)

I think I am clueless

[Elie]

I really like my Dual AMD CPU system, the Asus A7M266-D with the AMD 762 Northbridge and the AMD 768 Southbridge chipsets! never had an issue.

Note the differences between the AMD and VIA chipsets...

AMD 760MPX



VIA KT600



Now the AMD has it's issues with the 33mhz PCI bus, see how it connects to the southbridge, this is a bit constricting and I cannot put the RT.X100 in any 33Mhz PCI slot.
However look where the 66Mhz PCI slots are located, this proves to be more effeciant and in reality provides more bandwidth.
I have my RT.X100 in a 66Mhz slot running nicely.

With VIA however you still have a bottle neck and that is the path between the south and north bridge.

Cheers,
Elie

[Chrono_Wanderer]

hmm... that is a very smart design! no need to go thru the southbridge directly!

but what i don't get is why there is a bus between the CPU and the southbridge. What does that do?

[Elie]

Immediate processing of all the components directly attached to the southbridge I assume.

Someone could correct me if I am wrong.

Cheers,
Elie

[Nowhere]

Something with IRQs...

btw Elie & Doc, why I heard voices that AMD + Via combo board is inferior compared to pure AMD one? AFAIK pci controller is in the northbridge of AMD760, so although problems with hdd etc. because of via would remain, pci bandwitch should be ok...or perhaps Via ****ed their chipsets back then so badly that even connecting southbridge to otherwise good northbridge causes problems with pci?

[Chrono_Wanderer]

IMO, mixing up south and northbridges from different companies is a very bad idea... drivers... u know...

[Dr Mordrid]

Originally posted by Nowhere
Something with IRQs...

btw Elie & Doc, why I heard voices that AMD + Via combo board is inferior compared to pure AMD one? AFAIK pci controller is in the northbridge of AMD760, so although problems with hdd etc. because of via would remain, pci bandwitch should be ok...or perhaps Via ****ed their chipsets back then so badly that even connecting southbridge to otherwise good northbridge causes problems with pci?

AMD's isn't just connected to the northbridge but is instead used as the nb-sb interlink.

This harkens back to the old days wnen the nb-sb interlink was the PCI bus on most all chipsets and not a high speed dedicated bus like today. As such the PCI "interlink" was limited to 133 MB/s, the maximum throughput of the PCI bus itself. Each chip was on either the "north" or "south" end of the PCI bus, which became the source of the terms north-bridge and south-bridge.

Today AMD chipsets still use the PCI bus as the nb-sb interlink so they're bandwidth limited to 133 mb/s when using 33mhz PCI. AMD boards like Elie's that have a 66mhz PCI as the interlink get a boost in performance because that paticular PCI bus is twice as fast. Having the CPU's back-linked to the system management controller doesn't hurt either.

Still; 100% AMD chipsets with a 33mhz PCI bus/interlink do not have the PCI burst issue of VIA, which is the largest share of the bandwidth problem, and this gives them enough throughput to get by with high bandwidth cards & apps that use PCI devices.

The problem with AMD/VIA combo boards is that they don't use an AMD PCI bus as the interlink but VIA's conventional interlink and the PCI used is the one on the VIA southbridge, which brings along all of their PCI burst baggage.

Dr. Mordrid

[Nowhere]

I see Doc...but I must admit that I stiill don't fully understand your last sentence
You see, simple google image search ("amd 760 diagram" and "amd 760 scheme") revealed to me few block diagrams, on which it seems to me that traffic from northbridge to pci device avoids going through southbridge (and thus avoids problems coused by it) connected to this pci bus.
Perhaps I just don't fully understand the concept of bus in computers...
Thanks for trying to clear this up to me anyway.

edit: btw...
Anyone ever saw any pure single cpu AMD board for socket A in retail stores?

[Dr Mordrid]

Those diagrams show an AMD 760 north and AMD 766 south bridge, which in terms of the PCI being used both for the AMD nb-sb interlink and slots is best visuallized by this diagram;



When using the VIA southbridge one would have the choice of using the AMD PCI interlink for slots or using the PCI bus on the VIA southbridge. Guess which most makers did?

Examples of blended mainboard: Gigabyte GA7-DXR and GA-7DX+, Asus A7A266 and many others.

Yes, there are AMD/AMD boards out there but not many because most board makers opted for cost savings. Most today are dualies based on the AMD MPX 762/768 like the Tyan Tiger MPX S2466N-4M.

Dr. Mordrid

[bsdgeek]

Don't , I repeat DO NOT get an AMD/VIA combo board. As stated, it uses a VIA Southbridge, guess which one is most common. 686B. Yuck.

[Chrono_Wanderer]

wait... the A7A266 uses PCI as a NB-SB interlink?

edit: so ALi MAGIK1 actually has a better PCI than VIA's KT266? (or any K7 ViA chips)

oh yea... and does P4 VIA chips suffer the same PCI issue?

[Nowhere]

Don't worry, I won't. There's no point in it now I think...
And I'm using 686B right now
At least for what I use it it's...bearable (with latency patch of course)

[Dr Mordrid]

P4 VIA chipsets suffer the same problems.

I meant to type A7M266, not A7A266. A matter of thinking one thing and typing another.

I wouldn't go so far as to give the MAGIK1 credit for anything special in terms of performance

Dr. Mordrid