VAXP 1.2 and Hyper-X roadblock

To make a short story long, I recently purchased some Kingston Hyper-X Pc3000 for my VAXP/JIUHB T-Bred 'B' 1700 system. Prior to installing the Hyper-X, the system ran stably @ 2240 Mhz(14x160). This was while using Micron PC2100(2x256). Add the Hyper-X and...I can't boot above a FSB of 145! Now, the thing that appears strange to me, is that if I change the memory selection to DDR200(400Mhz), it'll run fine. Eazy-Tune tells me the DIMM is running at 402 Mhz, but I cannot bump the FSB past 145, even if the RAM is running at 266(133x2). Any ideas? Is the issue that I am using a single 512 meg module? SHould I exchange it for two sticks of 256? Help!

Running one DIMM instead of two, will reduce signal problems and electrical interference, so in theory should *improve* stability. Many motherboards don't even support the use of two or three DIMMs at the highest supported speed because of this.

If you are overclocking, make sure you set the DIMM speed to PC2700/DDR333. This will allow you some room to up the FSB before the memory becomes the bottleneck.

Ideally, you should always keep the RAM in sync with the processor FSB, meaning if the fsb is 145/290DDR, the ram should be running at 145/290DDR. This will A) reduce latency, hence speeding things up a little B) provide ample room for overclocking the FSB without RAM becoming a bottleneck.

Try upping the voltage of the DIMM if you cannot get it to run stable at a given speed.

It may or may not be the DIMM holding you back. You say you cannot boot past 145fsb, at those speeds it may be likely that one of your PCI devices or AGP card are giving out because of an overclocked PCI/AGP bus speed. Try kicking in the 1:5 divider if possible, if not you will have to auto-config the CPU to run at a 166mhz default fsb speed. (This involves joining one of the bridges on the CPU itself). By doing this, automatically kicks in the 1:5 divider (meaning AGP/PCI devices run at 1/5th the speed of the FSB instead of 1/4th). This should allow you to reach speeds upwards of 190fsb, without the AGP/PCI speed becoming a problem.

I was able to do this on my Athlon 1700+ (t-bred A) and my 7vaxp ultra. By doing this, the system will always run a default speed of 166fsb, which means you will probably have to drop the multiplier some, and increase the CPU voltage a little.

This often produces the highest performance on the GA-7VAxxx boards, because the fsb and RAM run in sync at high fsb's. There is no other way that I know of to, kick in a 1:5 divider, so unless you do this mod, you may be stuck at a 145mhz fsb.

Good luck!

BTW: If you still believe the RAM to be a problem, make sure "Top Performance" is DISABLED, and that RAM timings are relaxed or at stock speed (CTRL-F1 to access that menu)

Adelphia,

Thank you for the reply. The strange thing is, that I have had the system running stably at 160 FSB with the PC2100. Another oddity, is that if I set the memory selection to DDR400, it'll run at 402 Mhz DDR(according to EZ-Tune anyway). If this is accurate, then the RAM isn't the problem, in which case I must wonder, what is? I do not use the 'Top Performance' selection at all. At this point, I believe I will have to try running at 166 to change the divider. I don't believe there is a PCI speed-related issue, because of previous experimentation. I guess I just wonder whether I should exchange the RAM for another DIMM to see if it solves my problem. Thanks again.

At 160fsb, the PCI/AGP are seriously out of spec. Probably in the 40/80mhz range. I'm suprised you did not have problems as a result of this in your previous setup.

The fact that the RAM runs at 400mhz async, leads me to believe the problem is *not* the RAM. However that is debatable, and you may benefit (at least to eliminate one possibility) by exchanging it for another.

I don't think the 7VAXP will allow fsb's past 165 (1:5 divider is kicked in at 166) unless the CPU is the 333fsb variety (again this can be set to default by joining a bridge on the CPU).

One thing I do notice on my board, is that the RAM timings are adjusted according to fsb speeds. When set to AUTO, it will want to speed up timings at lower fsb's, and lower timings for higher fsb's.

You may want to enter the Advanced Chipset Features menu (CTRL-F1 in BIOS), and set the timings manually. Not sure what HyperX timings are but 7-3-3 with 2.5CL are pretty standard for most RAM. This *may* well be the problem, so have a look and see.

Good luck!