EggXpert

Have you ever been looking through the Newegg stock Motherboards, and seen, in the specs section, a specification for Northbridge and a specification for Southbridge? Ever really wondered what those are, and how they affect your system, your speed, your graphics, etc.?

I'll go as in depth into this as I can here, as a simple knowledge article on the topic.

Mind you, these are non-removeable chipsets on your Motherboard. You cannot upgrade them, etc. in any way other than switching Motherboards.

* * * * * * * *

The Northbridge and Southbridge are two very important 'tie-in' components on your motherboard. They handle communication between your CPU and connexions such as the AGP/PCIe, PCI, RAM and your USB interfaces.

You can divide up your standard interfaces into two categories: fast and not-as-fast (Some people would divide them into 'Fast' and 'Slow', but that could hurt your 'high speed' USB port's feelings... :). Once you divide your interfaces into these two groups, you'll see what is controlled by what. Falling into the 'fast' category are your RAM and your PCIe or AGP interfaces. These are connected to the Northbridge (I'll explain why in a minute). Falling into the 'not-as-fast' category is basically everything else: PCI, Power Management (APM), USB, your system clock, IDE connexions, and more.

"So," you may ask, "why call them the 'Northbridge' and 'Southbridge'? I mean, depending on how your computer's sitting, it doesn't need to be north and south, right?" Wrong. If you don't line them up exactly with north and south magnetic poles, your computer will spontaneously combust into a giant fireball, leaving a crater roughly the size of alaska, and at least as deep. Ok... Um, scratch that. Actually it's very simple to explain. I'll do a little text picture here:

 -----
|CPU|
 -----
   ||
 -----    ------------------
| NB |=|Fast Interfaces|
 -----    ------------------
   ||
 -----    -------------------
| SB |=|Everything Else|
 -----    -------------------

I've set it up here like a map (kind of) so it'll be easier to visualise.
-The Northbridge is connected to three things - the CPU, the Fast Interface Devices (which, I guess, is more than one thing, but for simplicity sake...), and the Southbridge. The Northbridge is connected directly to the CPU, which is why it handles the faster Interface Devices.
-The Southbridge is connected to only two things - the Northbridge and 'Everything Else' (conglomerated for the same reason as before). The Southbridge takes care of the slower Interfaces because it doesn't have a direct connexion to the CPU, and thus experiences a kind of degredation of performance. It also means that it doesn't have to be as fast, etc. as the Northbridge.

The Northbridge determines what series of CPU your motherboard will use, how many it can use, and what speeds are supported (because they're directly linked, if one is slower than the other going either way, there will be bottlenecking). It also determines the same for your RAM: what speed it can run at, how much you can use, and what type you'll use. Now, the Northbridge may seem like the main man here, but all this is, of course, also dependent on other factors (for example, if your Northbridge accepts multiple types of processors, you'll have to use one compatible with the socket on the motherboard. If the same Northbridge were on another compatible motherboard, it may enable you to use a different socket processor. The same goes for the number of available RAM sockets). The Northbridge is also what the CPU uses to define it's own frequency... which is why the Northbridge plays an integral part in overclocking. Because of this, many Northbridges now have heatsinks (to avoid melting, or maybe even spontaneous combustion, which can be fun! :).

The Southbridge must be designed to work with your specific Northbridge, because there is no industry standard for the Northbridge/Southbridge connexion (now, as to why, I don't know - you'd think it makes sense, no?). The Southbridge is located further away from the CPU than the Northbridge, and, as such, every little bit (get it? :) of information it sends has a longer distance to travel. This is why it handles the slower devices, because there's not as much an emphasis on speed. PCI, Serial and Parallel ATA connexions, Firewire, and more run through the Southbridge. In order for these devices to get CPU attention, the integrated interrupt controller (PIC - the 'P' is for 'Programmable', not 'Processor' or 'Pigeon') is used.

Separating the Northbridge and Southbridge is not necessary, as sometimes (read: rarely), when the factors permit, they will be placed together on the same die, and are utilised together. It probably saves on production cost, but seems like it'd be quite a hassle to get it to work correctly (it's always easier to build two small sandcastles than one large one).

Also, if you look at the model numbers or descriptions of motherboards, you'll see the name of the Northbridge (or some concatenated version of it) but not the Southbridge. Why? Because the Southbridge has to work with the Northbridge, so there's usually only a few (if not one) Southbridge in compliance. Because of this, the Southbridge suffers from low-self-esteem issues. ("Why doesn't anyone care about me?")

Did that video-card-looking mumbo jumbo on the Northbridges ever confuse you? Like, when you're looking through the specs, and it says something like "NVIDIA nForce 570 SLI MCP"? It's really just a descriptor, and I'm sure that if you read through the rest of the specs, you'd understand - but, for simplicity sake, I'm going to explain it here real fast: This specific one supports SLI, Multi-Core, and the nForce series. Though the specific Motherboard may not have enough PCIe slots for SLI, or whatever else, the support is there in the Northbridge, if the Motherboard wishes to utilise it.

* * * * * * * *

I hope that this clears up some questions, and maybe some other tech-heads like me will be able to better understand the workings of a computer by ingesting this. :) I had fun writing, and if you found it an interesting read, let me know - perhaps I'll delve into different areas later.

(If you see mistakes, or have additions, please let me know so I can change this OP and credit you. Thanks!)

Thanks for the post. Nice way of explaining everything! Nicely done

Nice article, thanks for shedding some light on this issue.

Thank you two.

I mean, you see things all the time on Processor Speeds and RAM and Configurations and Graphics Cards.  I just thought it'd be fun to explain one of the lesser-known topics, you know? :)

Any other semi-relevant or obscure hardware topics that anyone would like me to cover?

Thank you, you dumbed it down for me enough that I understood what you were talking about :)

TheLarrikin:

Any other semi-relevant or obscure hardware topics that anyone would like me to cover?

Lets see,

- The importance of ram in Overclocking

- Latency

- Typical Temps for various processors

- Effective airflow

- IDE vs SATA

Thats a start i guess....

Very nice

Thank you

Excellent job TheLarrikin.  

Slightly Intel cpu centric since AMD cpu based boards don't control memory through the Northbridge but from your thread most folks will have a much better understanding.

TempestKing, you might take a look here.  Might shed a little light on your memory and overclocking questions.

Nice article and easy to understand. thank you.

How's this, Tempest?

Edit: **Sorry! Double post!**

I really like where this is going, and I like your way of explaining these things. I have to ask tho, not as an attach or anything, but for documentation purposes what are your credintials?

~TK

Credentials. ;)  I've many, many credentials in too many areas to list (look through my posts, and I'm sure you'd agree :).

But, as for computers specifically, I worked very closely with quite a few engineers up until a while back, when I figured I'd do something else I enjoyed doing. :)  In fact, I don't think I've had a job that I haven't liked in some form or another. :)

I was working as a systems programmer, as in helping define certain computer programming languages, as well as creating interpreters for machine code, and actually writing BIOS for motherboards for some time.  I'm sure there's stuff of mine still floating about, but I'm sure you know I like to try to stay hospitable but foreign in this massive world that is the internet.

I'm fairly eclectic. (Don't judge me!) :)

Thanks for that, I just have some people that might question where i was getting this info, and thought It wouldnt be good just to say from some forum member in the internet... at least now it would sound much better. 

BTW these articles are eggcellent!

so a NVIDIA nForce 570 SLI MCP northbridge cant support a Geforce card?

I don't believe that's the case, but it's not optimised for it, and probably wouldn't give you the best results possible for your card.  I'm not sure, though, as I tend to match these up when building (kind of second nature).  Any other users out there with a possible answer for this?

Also, if the Northbridge is for SLI, you can't use it for Crossfire.

Edit: Let me clarify.  Since the PCIe and AGP ports are connected directly to the Northbridge, which defines what it does and does not support, I don't believe that another manufacturer would support video cards from a competing company.  I don't know if this is necessarily the case or not, but I believe it is, and I would not suggest mixing brands as stated in your previous post.

So the last time I overclocked and hit a wall with my old chip (AMD 5200+), it was suggested that I add a little voltage to my northbridge. Now I have an AMD 6000+, which took a new set of bios just so the mobo would recognize the chip model. I have a Gigabyte M59-SLI S5 (nForce 590 Chipset). Would it be advisable to raise the northbridge voltage a little again to adjust for the speed of this chip, or is that only something to worry about if I overclock again. When, if ever would you suggest raising the voltage on the northbridge? Southbridge?

To answer the easy question first ;) - I have never upped the voltage on my Southbridge.  The only time I could think about doing this would be in the rare instance that you run with a PCI graphics card or want a little more juice for your soundcard.  The USB won't change much, speedwise, and there's not much else there you need to fiddle with. But even the aforementioned situation is not common.

Now, for the Northbridge, it's common.  On your current processor, though, I wouldn't up it unless you want to overclock it, as well.  The new bios you installed probably already upped it a bit anyways, to support the faster processor speed (to prevent bottlenecking, per my OP).  If you find that you're not getting out of it what you want, go ahead and give it a little boost.  It should be common knowledge to do these in little steps, but I know some who have taken a jump and fried their board - then what good is a faster processor, huh? :)

So, basically, Northbridge is an integral part in overclocking, but should not be modified unless you are overclocking (or simply playing around).  I still see no reason to mess with the Southbridge.

* * *

I think now would be a good time to throw in a disclaimer: **I am not responsible for people screwing up their own stuff!  I am very knowledgeable on this subject, but not the high-and-almighty leader of Northbridge/Southbridge Information!  Remember, it's always good to ask around. :)**