ramashiva

I am very excited by BlueScreen's post revealing a supply source for k6-III+ processors. I can hardly wait to get my hands on one of these bad boys.

Meanwhile, I would like to share my experiences overclocking and tweaking my current CPU, a 500 mhz k6-III which I have running rock solid at 504 mhz (4.5x112) at 2.2 volts on a FIC VA-503A motherboard using a 128 mb stick of EMS ECC HSDRAM. This memory module is conservatively rated at CAS 3 at 133 mhz, although many internet reviews say it runs rock solid at 133 mhz at CAS 2, and at 150+ mhz at CAS 3. At 112 mhz I have this memory running with turbo BIOS settings, CAS 2, and zero wait-states. I can set the memory bus to 124 mhz and everything is still rock solid with the same BIOS settings.

The CPU is cooled by a cool-it-dude 40-watt peltier cooler from Computer Nerd. Under full load, the CPU temperature rarely exceeds 22 degrees C., and the two system chips run at about 25 degrees C. and 30 degrees C.

My previous CPU was a 2.4 volt 400 mhz k6-III. I had to struggle to get this processor to run stably at 448 mhz (4x112). Initially, I had to crank the voltage all the way up to 3.0 volts, and the CPU still crashed fairly frequently. After a burn-in period, the crashes stopped and I achieved stable operation at 2.8 volts.

Imagine how thrilled I was when my new 500 mhz CPU ran rock solid at 504 mhz at 2.2 volts right out of the box. I thought "This baby is going to hit 600 mhz without breaking a sweat." Unfortunately, this has not been the case, and I have been unable to achieve stable operation above 504 mhz.

I'm not sure if the limiting factor is the CPU, the motherboard, or the cooling. I'm pretty sure the HSDRAM is not the problem.

For those of you not familiar with the FIC VA-503A motherboard, a few important facts --

1. The motherboard is based on the VIA MVP3 chipset.

2. The motherboard has dipswitches to set CPU clock multiplier, voltage, and memory-bus speed.

3. The CPU front-side bus (FSB) speed defaults to the memory-bus speed, but can be independently set in the BIOS to 100 mhz, 112 mhz, or 124 mhz, regardless of memory-bus speed.

4. There is a special dipswitch setting which sets the memory-bus speed to 83 mhz and the FSB speed to 124 mhz. This setting is mainly for slower SDRAM (PC 66) which cannot handle 100+ mhz bus speeds.

All righty, then. When I set the CPU for 560 mhz (5x112) operation, it will POST just fine at 2.6 volts, but always crashes somewhere during the Windows 98 boot process. Upping the voltage as high as 3.0 volts does not correct the problem. Similar results are obtained at 550 mhz (5.5x100). As I said before, I don't know if this a CPU limitation, or if I need more cooling (such as a 78-watt Swiftech peltier), or a different motherboard.

The second frustration I have experienced is that I the only way I can get 124 mhz FSB speed is to use the special dipswitch setting which sets the memory-bus speed to 83 mhz. With this setting, everything works fine at 496 mhz (4x124). But if I set the memory-bus speed to 100 mhz, 112 mhz, or 124 mhz, the clock multiplier to 4, and the FSB speed in the BIOS to 124 mhz, the system will not even POST.

By the way, I have no problem setting the memory-bus speed to 124 mhz, as long as the FSB speed setting in the BIOS is 100 mhz or 112 mhz. Is this bizarre or what???

Has anybody had any success running any MVP3-based motherboard with both the memory bus and FSB running above 112 mhz? Yes, I know the Ali V based boards have this capability, but the Ali motherboards do not support ECC above 100 mhz. As far as I'm concerned, using non-ECC memory is pure insanity. ECC memory is only a little more expensive, and it gives you a definitive hardware check on the integrity of retrieval of information from system memory.

The Ali V chipset also provides better memory bandwidth than the MVP chipset, about 200+ mb/sec versus 150+ mb/second, as measured by SANDRA. Memory bandwidth is a weakness of all Socket 7 chipsets. I'm getting 160+ mb/sec on my current system, and can get up to 180+ mb/sec by tweaking all the BIOS memory settings aggressively with TWEAKBIOS.

I'm sure I could get a substantial boost in memory bandwidth by enabling 4-way interleaving. All 128 mb memory modules have four banks, so this would not be a problem. Unfortunately, my BIOS does not have settings for memory-bank interleaving, and, strangely enough, neither does TWEAKBIOS. I don't understand this, because I'm sure the MVP3 chipset supports memory-bank interleaving because the EPOX MVP3G series of motherboards have this setting in their BIOS. Oddly enough, so does the FIC VA-503+, the predecessor to the FIC VA-503A.

DOES ANYBODY KNOW OF A WAY TO ENABLE MEMORY-BANK INTERLEAVING ON MVP3 MOTHERBOARDS WHICH DON'T HAVE SUCH A SETTING IN THE BIOS???

Speaking of the EPOX MVP3G motherboards, they are the most likely candidate for me to get my k6-III to 560 mhz or higher. Supposedly, the original MVP3G-M (1 mb cache) is the fastest, as the memory settings on the MVP3G-2 (1 mb cache) and MVP3G-5 (2 mb cache) are more conservative to increase stability. Also, the MVP3G-5 supposedly has inferior tag ram, which supports the motherboard cache, and which makes stable operation at bus speeds above 100 mhz difficult or impossible. I would appreciate hearing from any MVP3G motherboard owners who have any definitive information on these supposed facts. More importantly --

HAS ANY EPOX MVP3G MOTHERBOARD OWNER BEEN ABLE TO RUN A K6-III AT 560+ MHZ, AND/OR ACHIEVE STABLE OPERATION WITH BOTH MEMORY BUS AND FSB RUNNING AT 124 MHZ?

SAME QUESTION FOR ANY OWNER OF A FIC VA-503A MOTHERBOARD OR ANY OTHER MVP3-BASED MOTHERBOARD.

A final note on k6-III performance --

It is important to enable both write allocate and write combining for optimum performance. If your BIOS doesn't have settings for these features, there are many utilities on the internet available for free download which enable these functions. If you can't find these utilities, and/or can't figure out how to use them, send me an e-mail and I'll give you some hints.

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William Coleman