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non-necessity of northbridges

what functions do northbridges provide? i realize theres a lot of I/ O breakout, but if you dont need the I/O, is there a compelling reason to keep the northbridge around? what processes does a northbridge streamline in system design, and what workarounds are required to omit it?

i'm thinking of two cases: a. VIA's new micro board at

formatting link
.... tiny cpu, huge chipset. b. power pc often has a 1000+ pin northbridge attached to it.

from a computer engineer standpoint, if you can omit it, i'd think it would save enormous design cost. if your cpu has gigabit ethernet and pci-express and you dont particularly want any of the plethora of miscellenary I/O northbridges provide, what would be the biggest stumbling blocks to removing the northbridge from the system. it seems like this peripherial bus controller is becoming largely obsolete, i'm just wondering whats involved in getting it out of the system, and what functions it provides that could be deemed not "peripherial" but "required".

rektide

Reply to
rektide
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Op Fri, 08 Jun 2007 02:40:39 +0200 schreef rektide :

Maybe you are confusing northbridge and southbridge? Since the =

northbridge connects to main memory, you'd definately want one of these.= =

But the southbridge can be slimmed down if you don't need PCI(-X/-E/etc.= ), =

ISA, IDE, audio, but you'd definately want to keep some southbridge =

functionality somewhere, since it also houses critical stuff like RTC, =

BIOS, DMA and interrupt controller. Unless of course you have a =

microcontroller that has these things on-chip, like a typical PowerPC.

The CPU in the article is not housed in a microcontroller because it is = a =

IBM-compatible x86 PC. Possibly the northbridge in the article has so =

much surface because it needs to connect 64+ pins from the CPU with =

64+ RAM pins and also 32+ AGP pins and maybe some other stuff as well. 
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Gemaakt met Opera's revolutionaire e-mailprogramma:  =

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Reply to
Boudewijn Dijkstra

Integrated memory controllers alleviate much of the need. BIOS is substituted by u-boot running on flash somewhere. DMA and interrupt controllers would be more problematic to replace, I'll have to see what the various PPC's have onboard for that.

Reply to
rektide

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