If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Can't "unsync" memory bus speed (A8V-E SE)
I have an Asus A8V-E SE motherboard (http://www.asus.com/products4.aspx?m...l2=15&l3 =143) with an A64 X2 4400+ (1 MB L2 cache for each core) processor. I cranked up the "FSB" speed from 200 to 220 MHz, effectively turning my 4400+ into a 4800+. Everything is running fine so far, but even after disabling the BIOS option for sync-ing the memory and PCI-E bus speed with the FSB (because I want the memory to continue to run at its stock speed for now), Everest and other such utilities report that the memory is also running at 220 MHz! How can that be when I've manually set it to run at 200 and not sync itself to the system bus? Any idea what I'm missing? I have good memory, so the overclock hasn't given me any problems, but just in case the memory does start to gag, I may have to reset everything back to stock speeds. That's no fun. |
#2
|
|||
|
|||
Can't "unsync" memory bus speed (A8V-E SE)
In article , "Hackworth"
wrote: I have an Asus A8V-E SE motherboard (http://www.asus.com/products4.aspx?m...l2=15&l3 =143) with an A64 X2 4400+ (1 MB L2 cache for each core) processor. I cranked up the "FSB" speed from 200 to 220 MHz, effectively turning my 4400+ into a 4800+. Everything is running fine so far, but even after disabling the BIOS option for sync-ing the memory and PCI-E bus speed with the FSB (because I want the memory to continue to run at its stock speed for now), Everest and other such utilities report that the memory is also running at 220 MHz! How can that be when I've manually set it to run at 200 and not sync itself to the system bus? Any idea what I'm missing? I have good memory, so the overclock hasn't given me any problems, but just in case the memory does start to gag, I may have to reset everything back to stock speeds. That's no fun. I don't think it works that way. The CPU external clock signal is 200MHz nominal. It is multiplied up by the CPU multiplier, then divided down by the memory divisor. In other words, the memory clock doesn't come from the clockgen, it comes out of the processor itself. If you get a copy of 26094 (note there is a different doc for AM2) from AMD and look at PDF page 114, the three bit field at the bottom of the page sets the memory divisor in an indirect way. The bit field values correspond to objective targets for memory speed, where the actual divisor used causes the memory clock to be less than or equal to the user desired target memory clock. http://www.amd.com/us-en/assets/cont...docs/26094.PDF That scheme works as long as the CPU external clock is 200MHz. When the external clock is scaled, the memory clock goes right along with it, because the logic inside the processor does not know any better. How the clock generator chip outside the processor is being (ab)used is none of the business of the processor's internal logic :-) Of course, a clever BIOS could select a lower objective value, to compensate for the level of overclock. For example, if you had DDR400 memory, overclocked the CPU by 10% from 200 to 220MHz, you could try to set the objective value to 183Mhz. 183 * 110% is 201MHz or so, which is close to the right value. AFAIK, the BIOS doesn't do that. Instead, it assumes the user will turn down the memory objective value. (At least it did on earlier Athlon64 boards.) This thread shows 8 columns, and I believe the 8 columns correspond to the bitfield bits 22 through 20 values. The second link here, is to the third table down on that web page, and shows what divider the processor uses, based on the CPU multiplier and the 3 bit field for the memclk setting. (Oskar Wu is the designer of the DFI Athlon64 motherboards.) http://xtremesystems.org/forums/show...hlight=divider http://oskarwu.myweb.hinet.net/A64D1.jpg To overclock, you crank the FSB and turn down the memory. This may be easier to do with a tool like A64tweaker, and there are probably other tools that can do it too (clockgen from cpuid.com ?). At least that may give you access to all eight possible values for the eight columns. As I don't have one of these boards, I don't know if the BIOS would offer more than the official objective values of DDR400, DDR333, DDR266, DDR200. (I notice in your manual, it has a different set of values, and I don't know how that lines up with the AMD 26094 document. Now I'm confused...) There is some info on A64tweaker here, and there are various versions floating around. Sometimes the earlier versions are what you are looking for. http://www.xtremesystems.org/forums/...t=37345&page=1 http://www.cranox.com/Software/A64-T...r_V0.6beta.zip In any case, cranking down the memory clock setting will fix the problem. HTH, Paul |
#3
|
|||
|
|||
Can't "unsync" memory bus speed (A8V-E SE)
"Paul" wrote in message ... In article , "Hackworth" wrote: I have an Asus A8V-E SE motherboard (http://www.asus.com/products4.aspx?m...l2=15&l3 =143) with an A64 X2 4400+ (1 MB L2 cache for each core) processor. I cranked up the "FSB" speed from 200 to 220 MHz, effectively turning my 4400+ into a 4800+. Everything is running fine so far, but even after disabling the BIOS option for sync-ing the memory and PCI-E bus speed with the FSB (because I want the memory to continue to run at its stock speed for now), Everest and other such utilities report that the memory is also running at 220 MHz! How can that be when I've manually set it to run at 200 and not sync itself to the system bus? Any idea what I'm missing? I have good memory, so the overclock hasn't given me any problems, but just in case the memory does start to gag, I may have to reset everything back to stock speeds. That's no fun. I don't think it works that way. The CPU external clock signal is 200MHz nominal. It is multiplied up by the CPU multiplier, then divided down by the memory divisor. In other words, the memory clock doesn't come from the clockgen, it comes out of the processor itself. If you get a copy of 26094 (note there is a different doc for AM2) from AMD and look at PDF page 114, the three bit field at the bottom of the page sets the memory divisor in an indirect way. The bit field values correspond to objective targets for memory speed, where the actual divisor used causes the memory clock to be less than or equal to the user desired target memory clock. http://www.amd.com/us-en/assets/cont...docs/26094.PDF That scheme works as long as the CPU external clock is 200MHz. When the external clock is scaled, the memory clock goes right along with it, because the logic inside the processor does not know any better. How the clock generator chip outside the processor is being (ab)used is none of the business of the processor's internal logic :-) Of course, a clever BIOS could select a lower objective value, to compensate for the level of overclock. For example, if you had DDR400 memory, overclocked the CPU by 10% from 200 to 220MHz, you could try to set the objective value to 183Mhz. 183 * 110% is 201MHz or so, which is close to the right value. AFAIK, the BIOS doesn't do that. Instead, it assumes the user will turn down the memory objective value. (At least it did on earlier Athlon64 boards.) This thread shows 8 columns, and I believe the 8 columns correspond to the bitfield bits 22 through 20 values. The second link here, is to the third table down on that web page, and shows what divider the processor uses, based on the CPU multiplier and the 3 bit field for the memclk setting. (Oskar Wu is the designer of the DFI Athlon64 motherboards.) http://xtremesystems.org/forums/show...hlight=divider http://oskarwu.myweb.hinet.net/A64D1.jpg To overclock, you crank the FSB and turn down the memory. This may be easier to do with a tool like A64tweaker, and there are probably other tools that can do it too (clockgen from cpuid.com ?). At least that may give you access to all eight possible values for the eight columns. As I don't have one of these boards, I don't know if the BIOS would offer more than the official objective values of DDR400, DDR333, DDR266, DDR200. (I notice in your manual, it has a different set of values, and I don't know how that lines up with the AMD 26094 document. Now I'm confused...) There is some info on A64tweaker here, and there are various versions floating around. Sometimes the earlier versions are what you are looking for. http://www.xtremesystems.org/forums/...t=37345&page=1 http://www.cranox.com/Software/A64-T...r_V0.6beta.zip In any case, cranking down the memory clock setting will fix the problem. Very interesting, and I appreciate the links. I wonder now whether the Asus BIOS really is being clever enough to maintain the nominal 200 MHz setting by cranking down the memory bus speed internally (to, say, 183 MHz as you suggest) to compensate for the higher (10 percent OC-ed) system bus speed. But you're right... if I should suddenly start having memory issues, I can always crank down the memory manually to allow for the higher multiplier. Fortunately, the Asus board is pretty accommodating and allows for all sorts of flexible tweaking. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
brand name ? | Jack Tseng | Asus Motherboards | 6 | August 28th 06 05:42 AM |
Bios settings for TWINX2048-3200C2 on Asus A8N32-SLI Deluxe ? | Skybuck Flying | Asus Motherboards | 16 | April 30th 06 09:45 PM |
Newby - [lease be gentle! | John | Homebuilt PC's | 11 | March 13th 05 10:14 AM |
still got performance problems with P4P800-E and Prescott | Johnny | Asus Motherboards | 13 | December 2nd 04 03:48 PM |
16mb buffer hard drive in a laptop | Dan Irwin | Storage (alternative) | 49 | November 4th 04 04:18 PM |