Today I use multiplier 8 cpu voltage 1.575 get the 285*8 successfully. cpu and mem all passed the prime95. the mem BW is crazy pc4560 with efficiency 85%=3870MB/s. the cpu now is 285*8=2280Mhz. but unfortunately it fails the 3d mark03 all 3d related things(even the dxdiag, but it gives me the hint for the reason and solution). For better understanding please refer to the graph for K8T800 Pro chipset http://www.via.com.tw/en/images/products/chipsets/k8-series/k8t800pro_blkdiagram.jpg or this page http://www.via.com.tw/en/products/chipsets/k8-series/k8t800pro/
You can see the important routes are Hypertransport and AGP 8X link, no matter how I adjust the setting, i can not get 3d workable under 285Mhz. Why prime95 can work perfectly but the 3D can not work??? Kula, do you notice a value when you do the sisoft sandra mem bandwidth test. It is named chipset 1 & under it "the Maximum Bandwidth". when I do testing @ 285 the value is 1140MB/s. I suddenly realize this is the key. it should be the "V-MAP" bandwidth in the figure above. according to the VIA, the V-MAP is the link between NB and SB, the bandwidth is as large as 1066MB/s. now you got it? yes the V-MAP speed is related to the FSB speed. When I touch it @ 285 Mhz, I feel it is very hot. So it further proves my point, when it is over roughly XMhz, it will be hardly cooled down. X/285=1066/1140 So X=266MHz. the Abit is really doing a good job on NB of this board, a nice blue heatsink. but Abit is really poor on SB, nothing onside the SB. So even @ speed>266Mhz, we can boot into windows, cpu mem testing, it is just hotter than @266 speed. when you doing the 3D game, it pushes the temp even higher!!!-----Beng! system hang for no reason, the nv_disp.dll can not receive the data it needed. Now not all the texture are in the memory, so this V-MAP link is so hot that nv_disp.dll will fall in a infinite loop to waiting for its large volume texture data to pass it to G-Card through HT and AGP8X link.
Now I am running 267*9( if it is not stable I will adjust it to 266), I believe my pc will be stable even @3D games.
For me 267*9=2400Mhz, the cpu is not so hot (much less than 2500MHz) mem is much much lower than my tested 285Mhz. what i will do is buy a small heatsink and put it on the SB to give SB a passive heatsink (I hv done that when I was doing my amplifier project at NUS). I believe after attached the heatsink, the board can run FSB285 very stable in all kinds of jobs. If possible I will attach a small fan to it to make it active heatsinker :-)
Rules of thumb so far I find
1)to increase the FSB to > 275Mhz, increase the cpu voltage, in my case I only can make it work when I adjust it to 1.575V. Mem timing is 3-4-4-8 at least for 285,actually I have not tested the other timing maybe it is really workable. Mem voltage here is 2.8v is enough for 285MHz. Cooling down the SB(south bridge) for our abit k8vpro board.
2)adjust the Htt mutiplier (3 for fsb>250Mhz) to make the whole bandwidth less than 2GHz.
what we can do in the future after apply the cooling system to SB, the reason why the fsb can not be pushed larger than 300+ is we need cool down the Sourth Bridge VT8237 chip. At that time, possiblly we can do FSB 342 with 6:5 ratio mem 285,342*8=2736MHz with maybe a good cooling fan or water cooling :-)
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