VOGONS


First post, by AJ49er

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Hey, interested to see who has been able to do what overclocking this processor and what you've done to get it there! For example, what's the highest without changing the standard voltage versus the highest stable overclock at increased?

Reply 1 of 12, by Anonymous Coward

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Maybe 120.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 2 of 12, by rmay635703

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My dx4’s overclocked el zilcho

The venerable dx33mhz I had was very overclockable
The sx25 and sx2’s were extremely overclockable
The dx2-50’s easily hit 66mhz but no more

My dx2-66’s were much more overclockable than the dx4’s

The 83mhz p24t’s would overclock but usually became long term unstable at 100mhz

My 5x86 ran fine at 150mhz but not at 160, never understood that.

Reply 4 of 12, by kixs

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I tested around 20 Intel DX4-100 SK096 (with WB cache) and most would work just fine at 120Mhz or even boot at 133. But only one is actually stable at 133Mhz (2x66). I didn't try 50MHz bus (3x50) as I don't think it's viable. I think I used 4V.

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Reply 5 of 12, by AJ49er

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Thank you for the responses guys. I'm at that point where I'm weighing up just trying to bump the FSB to 40mhz without messing with any voltage, I just don't have a replacement DX4-100 to replace it with though if something goes wrong. I guess if it can run with stock voltage at 40mhz then the heat shouldn't drastically increase?!

I have no real need to do it other than "why not?".

Reply 7 of 12, by Scali

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Running the FSB at more than 33 MHz can cause problems with the chipset and expansion cards, especially VLB ones.
The Intel 486DX-50 was short-lived because of that. 40 MHz is doable with most boards and cards, but 50 MHz is definitely an issue, and 66 MHz even moreso.

http://scalibq.wordpress.com/just-keeping-it- … ro-programming/

Reply 8 of 12, by kixs

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Scali wrote:

Running the FSB at more than 33 MHz can cause problems with the chipset and expansion cards, especially VLB ones.
The Intel 486DX-50 was short-lived because of that. 40 MHz is doable with most boards and cards, but 50 MHz is definitely an issue, and 66 MHz even moreso.

Unless the board has 1:2 divider for the bus. I used Gigabyte GA-486AM/S which has this option in BIOS.

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Reply 9 of 12, by amadeus777999

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I have one that I tested for a day at 133mhz on a LS486E.

Voltage used before the long term testing was 5V, which was a bit heavy, so I "installed", a voltage regulator and fiddled around until I got it stable with "minimum" voltage.
The problem that I had was the ram and cache which would not play along at 66mhz fsb. So I had to disable the cache and turn down the ram settings one notch(fastest to faster).

The system, even without 2nd lvl cache and tamer ram timings, bites pretty hard - 64fps in Doom timedemo demo 3 and 97.8fps in 3DBench2.
Write speeds are between 120- and 140Mib/s.
It is also one of the 486 that manages to play demo4 of the Ultimate Doom above 35fps which normally requires a higher clockable AMD and cache at the fastest settings.

I'll put together a 120/40 system with cache and see how this one goes as I have found no scores for such a system in my notes.

Reply 10 of 12, by AJ49er

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So I went ahead and did it with no increase in voltage (120/40) and initial outlook looks good. Doom bench went from 37fps to 45 and 3dbench2 went from 65.5 to just over 80 (can't remember the exact number). This is with 256mb cache, 64mb RAM so I'd be interested in more information on your 66mhz overclock!

Reply 11 of 12, by Disruptor

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AJ49er wrote on 2019-07-26, 14:51:

...
This is with 256mb cache, 64mb RAM so I'd be interested in more information on your 66mhz overclock!

Please remember that 256 kB cache in a 486 grants a cacheable area of 32 MB in write back mode and 64 MB in write through mode.
What SRAM and DRAM timings do you use?

Reply 12 of 12, by Mvickers03

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Thank you for this information, I’ve got one of these chips on order, and am hoping to achieve a 120/40Mhz FSB overclock.

Looks like with a little luck, I might be able to get that stable.