File Corruption and Integrated Chipset Motherboards

[melcom]

We've built 10 or more systems using K6-2-500 CPUs in the PC-Chips 585LMR PC100 mainboard which uses the Via integrated HT8501/82C686A chipset. Normally Win98SE. Seagate U8 or U10 UDMA 66 HDDs. We initially found that clocking them back to 450mhz solved a tendancy to instability so did that routinely. However at least half of them have at some stage experienced massive file corruption, typically with all the C drive root directory being deleted except for a dir named "Windows" which is empty except for an "All Users" sub dir, both dirs dated and time stamped when the machine was shut down at the end of its previous normal run. Not always is it exactly the same - sometimes "All users" is empty, sometimes it contains a line or so of garbage. The first sign of trouble reported by the user is when on switching on for the next session, it won't boot from the HDD because sysstem files can't be found. Scandisk run from the Win98 CD restores a partly workable system but with lots of DIR000nns. At first we suspected a virus, but haven't found any and several affected users seem at low risk.. Now we suspect the hardware, especially in the light of reports that some highly integrated chipsets can corrupt Linux systems. The Aps software has been pretty normal - Corel WP8 suite etc. Also Rain V1, which has seemed quite innocent on all other systems we build.
Any thoughts would be greatly appreciated. We feel close to recalling all these systems, but don't know what to do with them.

 

[Comtech]

I would recall them all, change the motherboards to something with an Intel BX or VIA Aladdin or Apollo Pro chipset, and send them all back out. I'll bet you can actually run these at the REAL 500mhz mark as well, and all your (seemingly) associated problems will probably disappear. Cheers,
Jim
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[CitrixEngineer]

Agreed, Comtech. These boards are not designed to run any faster than 450Mhz: By underclocking the processors, unless the core voltage and clock multiplier factors have been adjusted precisely, these symptoms are almost inevitable.

 

[Comtech]

Another thought.
Just HOW are you achieving the 450mhz?
Are you adjusting the multiplyer and/or the FSB?
A 6x75mhz will surely cause all the problems you're having, as well as a 6.5x66mhz would.
Even 4.5x100mhz may not be stable, as the FSB might be trying to run at 50mhz (FSB / 2) instead of FSB / 3.
Cheers,
Jim
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[melcom]

Thanks for the responses, folks. Sorry abt the time lapse - we're in our Christmas holidays.

We've used 4.5 x 100 and 5 X 90 - both seem ok for weeks on end. We tried settings (not available to me at present) to get 475, but that did NOT work. Presumably something (RAM or a peripheral) didn't like the resulting bus speed.

The manual for the mainboard says that the BIOS frequency setting sets the system bus speed, so I assumed that all other mainboard frequenies would be derived from that and would be standard if we used a 100MHZ setting.

The "multiplier setting" presumably sets the CPU frequency as a multiple of the bus speed.

4.5 X 100 would be the settings for a 450 mhz CPU. I thought that the only real difference between a 450 and a 500 CPU was the grading at the factory following the post-production tests, and that the mainboard would not be able to tell the difference if we used the 4.5 X 100 setting.

Am I missing something?

 

[CitrixEngineer]

All the technical information on this board can be found here:

http://www.pcchips.com/product.html

Note that PC Chips state that "First thing you have to check is the core voltage required for your new CPU".

Note also "After the correct core voltage is set, the next step is to determine CPU's external clock speed(or bus speed) and internal multiplier for Intel ` AMD or IDT CPU. The CPU speed equivalent to external clock speed(bus speed)times internal multiplier, but for IBM/Cyrix CPU, it use performance rating as the CPU speed, so you can not use the above formula to set the bus speed and multiplier. Reference Table 2 for the IBM/Cyrix CPU performance rating vs. Bus speed & multiplier, and Table 3 listed the recommend bus speed & multiplier for each speed of CPUs. (Note that the multiplier we recommend for the IBM/Cyrix CPU is always a integer, since it will cause the board more stability) Choose the bus speed and mulitplier you wanted and set the jumpers. "

Whether processors are the same speed with different factory gradings following internal tests or not depends on the manufacturer. You don't know if you've got a chip that's at the top or bottom of its grading - ie whether it was designed as a 500Mhz and passed, or designed as 750Mhz and failed several times until 500Mhz passed.

Changing the clock speeds of computers is OK for hobbyists, but not recommended for commercial use.

I hope this information is useful.