nForce3-250Gb: WORKING AGP/PCI Lock

It should not be a surprise that the first thing we confirmed is a working PCI/AGP lock. After discovering that none of the previous Athlon 64 chipsets had a working AGP lock, we went immediately to a test to verify that the AGP lock was indeed working. We used PC Geiger that was used for measuring PCI in PCI Speed and Overclocking: A Closer Look at A64 and P4 Chipsets. With FSB set at 249 and AGP frequency set to 67, we measured a PCI speed of 33.3MHz.

This is the expected results for a working AGP lock. We certainly can confirm that the AGP lock is working on the nForce3-250GB Reference Board, and we'll take another look when shipping nF3-250 boards start showing up in a couple of weeks.

FSB Overclocking Results

Reference Boards are not really designed for overclocking, and there are normally not any voltage adjustments available as we would see on production motherboards. However, with PCI/AGP lock available, we were anxious to see if the nForce3-250Gb did indeed overclock better. This was also an opportunity to verify a working PCI/AGP lock by a different method.

Front Side Bus Overclocking Testbed
Default Voltage
Processor: Athlon 64 3400+
CPU Voltage: 1.5V (default)
Cooling: AMD Stock Athlon 64 Heatsink/Fan
Power Supply: Powmax 350W
Maximum OC: 2442MHz (+11%)@222x12
2375Mhz@250FSBx9.5 (+25% FSB)

The above overclocking setup at default voltage allowed us to reach a stable Frequency of 250 at 800 HyperTransport with AGP/PCI fixed at 33/66. The limit of this CPU at default voltage is apparently somewhere around 2450MHz, since we could not reach 250FSB with a 10 multiplier. That would have represented 2.5GHz, had we been successful.

Important here is the fact that we reached the absolute highest FSB setting of the Reference Board, which is 250. This is further evidence that the AGP lock is indeed working on nforce3-250.

We asked nVidia about the issues with the nForce3-150 AGP/PCI lock, which are apparently fixed in nF3-250. nVidia assured us that the AGP lock was indeed working in the 150 Reference Board, but that the BIOS implementations by manufacturers with the 150 chipset were not correct. Therefore, the shipping boards for nF3-150 did not have a consistently working AGP lock. nVidia also assured us that they were working more closely with manufacturers on the nF3-250 launch to make sure manufacturers were delivering nF3-250 boards with working AGP lock.

We tested nVidia's claim and found the Reference nF3-150 board did have a working AGP lock. The AGP lock is also definitely working on the 250 Reference Board, and we sincerely hope we will find the same working lock on shipping nF3-250 motherboards. We will be looking closely at production nF3-250 boards to verify a working AGP lock.

Reference Boards are rarely a good indication of the true overclocking abilities of a chipset because they are designed to qualify and demonstrate a chipset at design parameters. The features are definitely here for the best overclocking in current Athlon 64 chipsets. It is also worth mentioning that the Athlon 64 Multiplier Utility, available as shareware from CPU-Z, worked fine on the nForce3-250. While it was designed for the 150 chipset, nVidia saw no reason why it should not work properly and we did confirm that the multiplier adjust utility works.

nForce3-250Gb Reference Board: Basic Features nForce3-250Gb: On-Chip Gigabit LAN


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