Using The K6-III on Older Boards

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The FIC PA-2007 1MB

The second motherboard we tested is the FIC PA-2007 rev 1.2 w/1MB. This motherboard is limited to a 10A maximum current, which would mean we cannot run either the K6-2 400 (10.3A) or K6-III 400 (11.1A) at full speed. In order to determine the maximum recommended speed we should run the processor we use the charts in our CPU Power Requirements article. By dividing the maximum current draw for both processors, and dividing by the voltage we get the total current draw. We then divide that number by 400, to get the Amps per MHz number. Now we can multiply that by any speed to determine the approximate current draw.

For the K6-2 processor, the fastest speeds we can run without exceeding 10A is 366MHz (5.5 x 66MHz = 9.45A) and 375MHz (5.0 x 75MHz = 9.7A). With the K6-III, we must run at a slower speed – either 333MHz (5.0 x 66MHz = 9.3A) or 337.5MHz (4.5 x 75MHz = 9.4A). Though some PA-2007 motherboards are capable of 75MHz, ours is not so we could only test the K6-2 at 366MHz vs. the K6-III at 333MHz. The question is obviously whether running the K6-III at 333MHz is even worth the trouble. In addition, the motherboard does not have the ability to run at 2.2V, but has a 2.3V setting as well as a 2.4V. In fact, this board has only three possible sub-2.5v settings: with 11-12 jumpered the voltage is 2.09, with 7-8/11-12 jumpered the voltage is 2.39v and with 9-10/11-12 jumpered the voltage is 2.31v.

The test setup included the PA-2007 rev 1.2 board with1MB onboard cache (BIOS Level 1.13CD15)), 64MB PC66 SDRAM, Western Digital 1.2GB (PIO 4) HDD, Diamond FireGL 1000 Pro w/ 8MB (BIOS Level 1.54), Windows 98 (release 1), DirectX 6.1 and Diamond 4.10.01.2359 video driver. The BIOS settings were set to ‘Setup Defaults’, and the display properties were set to 1024×768 and 16 bit color. The benchmarks run were Winstone 99, 3DMark99 Max Pro and Rage’s Incoming game benchmark.

CPUSettingWinstone 993DMark99 Max Pro
CPUMarks
3DMark99 Max Pro
3DMarks
Incoming
Worst FPS
Incoming
Best FPS
Incoming
Avg FPS
K6-2 3665.5 x 66MHz14.6430678710.2731.8619.76
K6-III 3335.0 x 66MHz17.4501984511.8731.9120.47

Just as with the P55T2P4, the Winstone 99 improvement with the K6-III is very impressive, but even more so here because it is running at 33MHz slower than the K6-2 366. In fact, in looking back at the scores on the P55T2P4, we find that these scores are only slightly slower. This can be attributed to the fact that more cache is involved and that SDRAM is being used instead of EDO. the 3DMark99 Max Pro and Incoming results were also very close to the P55T2P4 – definitely not attractive to the hardcore gamer, but impressive nonetheless for a two year old motherboard and a severely underclocked processor!

The voltage regulator heat sinks were barely warm during these tests – much cooler than the P55T2P4 voltage regulators were. Since we know that there are always those who wish to ‘push the envelope’ a bit, we ran a Winstone 99 test with the K6-III running at 400MHz which resulted in a score of 18.5. One minor issue is that the BIOS only recognized the proper K6-III speed up to 366MHz, showing the string “K6-III at 256MHz” when set to the 400MHz speed. Based upon these results, it may not be worth the risk to run at 400MHz. If your particular PA-2007 has support for a bus speed of 75MHz, you might get slightly better results using that setting.


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