NForce

2019-01-25T09:59:09Z

Dans34: Slight AMD Heritage correction

{{retrieved|http://www.xbox-linux.org/wiki/NForce}}

This documents collects information about the Xbox chipset and its sibling, the nVidia nForce chipset, as well as further relatives.

== nForce ==

The nForce chipset consists of the IGP (Integrated Graphics Processor) Northbridge and the MCP (Media and Communications Processor) Southbridge. Both are available in different flavours:

* IGP-64: 64 bit memory bus
* IGP-128: 128 bit memory bus (TwinBank), requires two DIMM modules for 128 bit operation
* MCP-D: includes Dolby Digital encoder
* MCP: Dolby Digital encoder disabled

So these are the four possible combinations:

{| class="wikitable"
|-
|
| MCP
| MCP-D
|-
| IGP-64
| nForce 220
| nForce 220D
|-
| IGP-128
| nForce 420
| nForce 420D
|}
[https://web.archive.org/web/20100617023830/http://www.theregister.co.uk/2001/05/31/nvidia_crush_chipset_named_nforce/]
[https://web.archive.org/web/20100617023830/http://www.theregister.co.uk/2001/06/01/nvidia_crush_is_called_nforce/]

The VGA controller inside the IGP is a "GeForce2 MX Integrated Graphics" (PCI ID:10de/01a0). Its internal name is NV1A.

[https://web.archive.org/web/20100617023830/http://pciids.sourceforge.net/iii/?i=10de]
[https://web.archive.org/web/20100617023830/http://www.nvitalia.com/articoli/editoriali/produzione_nvidia_2001.htm]

Although IGP-64 and IGP-128 are different and their respective chipsets have different codenames (Crush11 and Crush12, see below), there seems to be no difference from the software side:

* The VGA BIOS of the MS-6367 mainboard (nForce 420D configuration, i.e. Crush12) has the internal name "CR11BT.ROM". It also includes the strings "NVIDIA GeForce2 Integrated GPU", "CR11 Board" and "Chip Rev B2".
* The PCI IDs seem to be the same for the GPUs inside IGP-64 and IGP-128.

== Crush ==

"Crush" was the codename of the nForce chipset. Crush11 is the nForce 220/220D/230/230-T, Crush12 is the nForce 420/420D/430/430-T, and Crush18 is the nForce2. The "11" probably derives from "NV11", the internal name of the GeForce2 MX.

[https://web.archive.org/web/20100617023830/http://users.erols.com/chare/chipsets.htm]
[https://web.archive.org/web/20100617023830/http://www.theregister.co.uk/2000/11/17/nvidias_super_secret_crush_spec/]

== nForce & Xbox ==

The Xbox has an IGP-128 that uses an NV2A video core (PCI ID:10de/02a5), which is between the GeForce3 (NV20) and the GeForce4 (NV25). The Southbridge is called "MCP-X" and lacks the PCI card bus (PCI bus #1).

[https://web.archive.org/web/20100617023830/http://www.digit-life.com/articles/nvidianforce/]
[https://web.archive.org/web/20100617023830/http://www.anandtech.com/showdoc.html?i=1484]
[https://web.archive.org/web/20100617023830/http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=1535]
[https://web.archive.org/web/20100617023830/http://www.anandtech.com/systems/showdoc.aspx?i=1561&p=3]

== AMD Heritage ==

There is the following rumour, which is not fully verified yet:

* Microsoft wanted AMD to make the CPU and the chipset for the Xbox, and nVidia to make the video hardware.
* When alpha hardware had already bee built, Intel made a better deal
* Microsoft agreed to have Intel CPUs; Intel had to modify AMD's chipset to support an Intel CPU
* Intel insisted that the brand name AMD could not be associated with the Xbox, so nVidia licensed the AMD chipset. Now the Xbox chipset was by nVidia.
* nVidia sold the same chipset for PCs, calling it "nForce".

This is the reason why

* the Xbox is the only nForce chipset with an Intel CPU
* the AMD chipset and the nForce chipset are so similar

Evidence:

* The AMD and nForce AMD IDE controllers are fully compatible. (Linux kernel: "AMD 755/756/766/8111 and nVidia nForce/2/2s/3/3s/CK804/MCP04 IDE driver for Linux." [https://web.archive.org/web/20100617023830/http://lxr.linux.no/source/drivers/ide/pci/amd74xx.c])
* The I2C/SMBus controller on the nForce is fully AMD-756/766/68 compatible. [https://web.archive.org/web/20100617023830/http://lxr.linux.no/source/drivers/i2c/busses/i2c-amd756.c]
* The audio controller is i810 compatible - as is the audio controller of the AMD-768 and the AMD-8111.
* The nForce and AMD-768 modems are compatible.
* At least one register ("VGA_en") in the nForce PCI-to-AGP bridge is compatible with the AMD chipset (AMD-761, 24081.pdf, page 136).
* The nForce uses HyperTransport.
* [https://web.archive.org/web/20100617023830/http://www.uwsg.iu.edu/hypermail/linux/kernel/0307.3/0922.html], [https://web.archive.org/web/20100617023830/http://www.uwsg.iu.edu/hypermail/linux/kernel/0301.3/0305.html]
* ''"One man's guess, the silicon is not a major factor. Because the nForce and 760 MP have a similar pin count, they are going to be cost comparable."'' [https://web.archive.org/web/20100617023830/http://overclockers.com/articles446/]

{| class="wikitable"
|-
|
| Northbridge
| Southbridge
|-
| AMD-760
| AMD-761
| AMD-766
|-
| AMD-760MP
| AMD-762
| AMD-766
|-
| AMD-760MPX
| AMD-762
| AMD-768
|}
[https://web.archive.org/web/20100617023830/http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_873_1133,00.html AMD-760™ Chipset Tech Docs]
[https://web.archive.org/web/20100617023830/http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_739_1130,00.html AMD-760™ MP Chipset Tech Docs]
[https://web.archive.org/web/20100617023830/http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_873_4296,00.html AMD-760™ MPX Chipset Tech Docs]
<br />
The nForce chipset might be based on the AMD-760 chipset.

== More Links ==

[https://web.archive.org/web/20100617023830/http://www.duxcw.com/digest/guides/mb_chip/nforce/print.htm]

xboxdevwiki - User contributions [en]

NForce