what are the north and south bridge on a mobo? and what is the difference between these 3?

North: SIS 648FX
South: SIS 964

Norht: Intel 865PE
South: Intel ICH5

North: VIA PT880
South: VIA VT8237

Generally, I like Wikipedia for "definition" questions like this. Unfortunately, when I Googled, it came up in Spanish. Here's the definition, or answer to what is NorthBridge:

El Northbridge ("puente norte" en inglés) es el chip más importante del conjunto de chips (Chipset) que constituye el corazón de la placa madre. Su función principal es la de controlar el funcionamiento del bus del procesador, la memoria y el puerto AGP. De esa forma, sirve de conexión (de ahí su denominación de "puente") entre la placa madre y los principales componentes de la PC: microprocesador, memoria RAM y video AGP.

I speak some Spanish and my take on the translation, along with what I know, is this: The NorthBridge is the most important of the chipsets that constitute the heart of the motherboard. Its principal purpose is to functionally control the processor bus, memory and AGP port [video port--so it could also be PCIe16, depending on the motherboard configuration] It services connections for the entire motherboard and the principal components of a PC: microprocessor, RAM memory, and video.

The SouthBridge is another chip on the motherboard that controls onboard devices including the IDE bus and PCI bus--and now SATA. I believe it also controls things like ethernet I/O and possibly onboard sound, USB and firewire--though I'm not positive about those last three. The SouthBridge is not directly connected to the CPU. Rather, the northbridge ties the southbridge to the CPU. They are called the North and South Bridges because of their physical locations relative to the CPU on the motherboard.

The chipset identities you list are from different manufacturers (SIS, Intel, and VIA--now also nVidea) and different series' from each. The series numbers (e.g., 865PE and ICH5..for Intel I/O Controller Hub Version 5) define what combinations of functions and device configurations are supported.

I'm not familiar enough with the specific variations to provide you with detailed difference information off the top of my head without more research, which I don't have time to do right now. Maybe one of the others here will fill in the gaps. Saphalline, our resident hardware Guru, has explained this before,. You could look around for his post.

Generally speaking, I think Intel and nVidea are the "higher end" chipset controller manufacturers and SIS and VIA are considered more as "economy". Still, they all provide equivalent functionality support. Meaning control of the hardware components/functions mentioned

These definitions are becoming more and more blurred lately. Any system based on AMD's K8 CPU's (Sempron64, Athlon64, X2, FX, Opteron) have an onboard memory controller, so the use of a classic Northbridge and Southbridge are unnecessary. But that's getting ahead of things. Here's a basic run-down:

Northbridge

The Northbridge is responsible for controlling the data flow from the CPU to the RAM, providing system timings via the RTC (real-time clock), serving as the AGP controller, and communicating with the Southbridge. In a classical chipset, such as the ones Intel uses (like the i945/i955 series), the majority of the transistors in the Northbridge are dedicated to the memory controller.

The memory controller handles translation duties from the CPU's FSB to the RAM and back. This means that it must maintain the FSB separately from the RAM bus because these two are not directly connected. Intel's FSB speeds now include 533MHz, 800MHz, and 1066MHz (not widely used yet) in a 64-bit quad-pumped arrangement (4 x 133MHz, 4 x 200MHz, and 4 x 266MHz, respectively). Likewise the RAM configuration can be single-channel (64-bit) or dual-channel (128-bit) at supported DDR2 speeds of DDR2-400, DDR2-533, DDR2-667, and sometimes DDR2-800+. So the CPU requests data from RAM, the memory controller in the Northbridge then translates that, gets the data from RAM, and gives it to the CPU. The memory controller is there to act as the middleman and keep the FSB and RAM bus separate and happy.

Other duties for the Northbridge are fairly self-explanatory, such as the AGP controller (bus interface for AGP vid cards - no longer present on modern PCIe chipsets), and the system clock management (low-level interface with the RTC, which is itself a mini-chipset). The connection to the Southbridge has been necessarily improved by great leaps and bounds in the past few years due to more raw system bandwidth introduced with new busses like USB 2.0, SATA, and PCIe. Older chipsets had North-to-Southbridge bandwidths on the order of just a few hundred Megabytes per second, with modern chipsets pushing several Gigabytes per second! :eek: Overall system performance has increased noticeably because of this.

In the case of AMD's K8 CPU's, the memory controller is integrated into the CPU die. Since two of the Northbridge's primary jobs are now gone (memory controller and AGP controller) there's not really much point in a Northbridge, is there? :p The RTC management has also been retained to the memory controller, so the RTC signal is piped directly to the CPU to the onboard memory controller and is then distributed to the rest of the system in a traditional sense. Except that it's on the CPU now. So, where does that leave the Northbridge? Well, with the exception of older K8 w/ AGP chipsets, there is no Northbridge. There's just a Southbridge, which has been renamed to just "the bridge". No need for a Northbridge anymore...

Southbridge

The Southbridge gets no respect! Honestly, most chipsets are named after their Northbridge, like the example of Intel's i865PE. That is more or less the "name" of the chipset. But the Southbridge actually does a lot of the grunt work. Just as the Northbridge is responsible for memory duties, the Southbridge is responsible for storage duties. IDE/ATA, SATA, PCI slots, USB, PS/2 ports, PCIe slots - pretty much every expansion port or slot or bus goes through the Southbridge. So it has a lot of jobs, but not a lot of constant activity. Whereas the memory controller can typically handle loads of Gigabytes per second from the RAM to the CPU and back, the Southbridge's storage busses rarely get as saturated. Just half a Gigabyte in a second is a huge load for the Southbridge! But the connection between the two bridges must be wide to account for low-latency requirements, like say using your mouse in a game! The signals from the mouse go through the PS/2 or USB bus, into the Southbridge, up to the Northbridge, then finally to the CPU. That's quite a journey! And the whole path must remain fast and responsive in order to work.

Northbridges also define a platform that is used - such as the socket interface for the CPU and the RAM that can be used. The Southbridge, however, defines the storage and expansion options. As such, most Northbridge chips are able to interface with many different Southbridge chips. So in the example of Intel's i865PE again, we see that either the ICH5 or the ICH5R can be used. The ICH5 is quite a capable Southbridge, but the more expensive ICH5R has built-in RAID capabilities. When a mobo manufacturer is designing a new mobo, they have the option of choosing which Southbridge to use with a Northbridge. This separation in the duties of the chips in the chipset allows a wider range of mobo's to be created with very little extra effort.

In the case of AMD's K8 CPU's, this choice is more or less limited to which Bridge to use. The idea of a "chipset" becomes less exciting. :p

As sort of a footnote here, the BIOS/CMOS combo is also connected to the Southbridge. This is more of a convention these days than a set rule, but is usually true for all modern chipsets.

Onboard functions

When it comes to things like onboard audio or that built-in LAN we've all come to appreciate ;) these extra functions are often found in the forms of extra chips. They become part of the chipset because they represent an entire "platform solution" that describes the capabilities of a mobo. Most often on modern chipsets, the onboard GbE (Gigabit Ethernet) is connected to the Southbridge via a PCIe x1 bus.

Onboard audio is given a specialized direct-connection to a Southbridge, making it proprietary for each series of chipset. As long as an audio chip can communicate on this direct-connection, it can be offered as an onboard audio solution to that chipset. Not all mobo's with onboard audio offer the same audio chip, either. Some use the standard chip recommended by the chipset manufacturer, others use another more powerful chip. There's no set number of options here, but most chipsets have at least two audio chips that can be paired with it.

Any sort of third-party RAID or SCSI (or other) controller chip will also be connected to the Southbrige. These are usually given their own PCI, PCIe, or PCI-X bus connection. The BIOS for these extra controller chips will be connected to them, not the Southbridge. Any onboard/integrated RAID functions that are specific to a chipset will reside within the Southbridge chip itself, though. There is no external chip for that.

Conclusion

As a final note, the terms "Northbridge" and "Southbridge" were given to chips within a chipset because of their logical orientation. The CPU is always considered the "top" or "North" of any system, and since the Northbridge is connected to the CPU, it was coined with "North". Likewise, the Southbrige is further down, and coined with "South". There have been chipsets in the past that have used terms like "Westbridge" or "Eastbridge", too, as well as chipsets having multiple Northbridge chips and/or Southbridge chips. In fact, the reason that Intel now refers to their Southbridge chips as ICH's, or "I/O Controller Hubs" is the fact that with the i815/i810 series, they merged their previously two Southbridges into one. Thus the "Hub" part of it. The history of chipsets is strewn with mobo's having lots of individual controller chips all over the place (anyone remember the Super I/O chips? :p) that have been merged into what we now know as "chipsets".

that was alot of information. let me say that again. that was alot of information.
so thank you a million for it.
now that i know what the north and south bridges are, do you know of anyway to compare the 3 sets i listed above

North: SIS 648FX
South: SIS 964

Norht: Intel 865PE
South: Intel ICH5

North: VIA PT880
South: VIA VT8237

thanks again! :D

If you're comparing chipsets to use with a Socket 478 P4/Celeron system, I'd say go with Intel's chipsets. Either the i865PE/G or the i875P. These chipsets support AGP 8x/4x as well as two native SATA ports built into the Southbridge (these were the first chipsets to have native SATA ports). These chipsets are powerful and easy to work with (from a driver & BIOS perspective) and I wholeheartedly recommend them.

A bit older technology than what you can get these days, but still cream-of-the-crop for Socket 478 systems.

so those intel ones are the ones you would recomend?
&
which of these is better for the north bridge (both intel) 865PE or 865G?

thanx again

The only difference between the i865PE and the i865G is that the i865G has onboard video. On the other hand, this also affects how those mobo's are designed. Since the i865G has onboard video, it's seen as a "cheapo" chipset (despite its powerful capabilities) and so is often stuck on micro-ATX mobo's with limited expansion. As such, I would actually recommend the i865PE.

Computers are all about complexity. :rolleyes:

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i should have read the other post.
i found the 1 i want YAY.
u guys have been a great help. im going 4 this (http://www.newegg.com/Product/Product.asp?item=N82E16813135152) one. unless anyone knows of a better one for around that price.

Looks good.

Yeah, I must admit that looks like the best one in that price range. It's funny, though, I thought those mobo's had come down in price. I guess not! :p

The next good one I would recommend would be the Asus P4P800SE (http://www.newegg.com/Product/Product.asp?Item=N82E16813131484), but that's nearly twice as much! :eek: Woah...

well thanx everyone. ill see if i can get that ordered 2night!