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AMD 5x86 @200

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First post, by stalk3r

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I'd like to try my 5x86 run at 200 Mhz on a VLB motherboard (Shuttle HOT-419). It is stable both at 160 (4x40) and 150 (3x50). Now, I have set everything to fail-safe in BIOS but it doesn't even boot at 4x50. The CPU voltage is still at default 3.45V. Can I safely go up to 4V? I read somewhere that going up to 5V can fry the L1 cache which I would avoid if possible. Also is there anything else I should turn off?

Last edited by stalk3r on 2019-07-09, 22:00. Edited 2 times in total.

Reply 1 of 39, by Intel486dx33

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I have mine stable at 160mhz. with jumpers at 4x40 at 2.2volts.
I never tried 200mhz. but some mentioned that you need to increase the voltage. I would not go beyond the default recommended voltage.
You will ruin your CPU.
I did not find much of a performance increase going from 133mhz to 160mhz.
So the performance increase is going to 200mhz will be marginal.

Last edited by Intel486dx33 on 2019-07-09, 19:38. Edited 1 time in total.

Reply 2 of 39, by derSammler

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I've tried three different AMD X5-133 CPUs myself and not a single one worked at 200 MHz. 4V did not help either. The screen didn't even come up. You must have lots of luck finding one that works at 200 MHz at all, let alone being stable.

If you are after speed, try finding a Cyrix 5x86 120 MHz and let that run at 150 MHz. It will outperform the AMD.

retro-net.de/blog.html

Reply 4 of 39, by stalk3r

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derSammler wrote:

4V did not help either

But it didn't fry it either? 😀

derSammler wrote:

If you are after speed, try finding a Cyrix 5x86 120 MHz and let that run at 150 MHz. It will outperform the AMD.

It is difficult to find such CPU nowadays (and expensive too).. it is more the achievement I am after.

Intel486dx33 wrote:

Phil has a video on this.
https://youtu.be/jlQXS1VrFUQ

Thanks for the link

Reply 5 of 39, by derSammler

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stalk3r wrote:

But it didn't fry it either? 😀

No, but it didn't make a difference. Those CPUs are not comparable with modern CPUs anyway, where overclocking involves raising the voltage level.

Also, the timings / BIOS settings are most likely not the problem. You would see the POST being executed otherwise at least. If the screen stays black, the CPU does not even execute the BIOS, simply because it can not handle the given speed. The only thing you can try is using faster RAM and removing the L2 cache from the board. If still nothing happens then, you're out of luck with the CPU you have.

retro-net.de/blog.html

Reply 6 of 39, by The Serpent Rider

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As I've mentioned here, it's possible with the temperatures below zero and SSTV2 practical test showed some potential.
But on normal conditions? Nah, not going to happen. Maybe if you cherry pick from few dozens CPUs, but only maybe.

Reply 8 of 39, by stalk3r

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The Serpent Rider wrote:

As I've mentioned here, it's possible with the temperatures below zero and SSTV2 practical test showed some potential.
But on normal conditions? Nah, not going to happen. Maybe if you cherry pick from few dozens CPUs, but only maybe.

I've found another guy who was successful with the sub-zero method, at -72 Celsius degree to be more specific

Lh6nnQZ.jpg

Now the question is, where to get this cooler? 😀

Reply 9 of 39, by cyclone3d

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I have one of those coolers that I picked up off of eBay for basically thew shipping cost. It doesn't cool though. Guessing the freon needs to be recharged. I just haven't had the time to mess with it yet. Was planning on seeing if I could get a K6-III+ to run at 720Mhz.

That being said.. .kind of a waste of electricity to just get an AMD 5x86 to run at 200Mhz. What is the point? Might as well just use a Pentium with an air cooler.

Well I guess if you really must have VLB then there is a case.. but why?

This is coming from someone who has overclocked pretty much everything since the 486SX-25 days.

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Reply 10 of 39, by Garrett W

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Instead of a 5x86 at 200, if you want to get your fast 486 dose, you can always try a Cyrix MediaGX. I happen to have a MediaGXm 266 that runs happily at 300MHz, made for some interesting comparisons with a Pentium 133 😀.

Reply 11 of 39, by treeman

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Intel486dx33 wrote:
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I have mine stable at 160mhz. with jumpers at 4x40 at 2.2volts.
I never tried 200mhz. but some mentioned that you need to increase the voltage. I would not go beyond the default recommended voltage.
You will ruin your CPU.
I did not find much of a performance increase going from 133mhz to 160mhz.
So the performance increase is going to 200mhz will be marginal.

going from 133 to 200 is about 50% increase hardly marginal not to mention going to 50fsb vs 40fsb boost

Reply 12 of 39, by derSammler

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He's probably refering to the increase in performance from 160 MHz to 200 MHz. From 133 to 160 give you a boost of 20%. From 160 to 200 gives you an additional boost of 25%. Now 25% may or may not be marginal, depending on your notion, but keep in mind that almost every VLB card requires to set a wait state when the FSB is running at 50 MHz. So you lose what you gain somewhere else (graphics most likely, which isn't what you really want if you are after performance).

Also, normally only one VLB card will work at that speed. If you have more than one VLB card installed, 50 MHz is normally a no-go, as it either doesn't work at all or very unstable.

retro-net.de/blog.html

Reply 13 of 39, by stalk3r

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derSammler wrote:

Also, normally only one VLB card will work at that speed. If you have more than one VLB card installed, 50 MHz is normally a no-go, as it either doesn't work at all or very unstable.

Mine is stable at 3x50 MHz with two VLB cards; a video and a multi i/o. I had to lower the DRAM timings a bit though, this I'll try to fix by throwing 60ns modules in instead of 70. Difference in performance is negligible between 4x40 and 3x50, with lower DRAM timings and VLB WS 1 for the latter.
------3x50 4x40
Doom 1359 1323
Topbench 355 359
Chris 3D 60.3 62.7
3dbench 83.3 90.9
LM20 503 535

Reply 14 of 39, by derSammler

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Difference in performance is negligible between 4x40 and 3x50, with lower DRAM timings and VLB WS 1 for the latter.

Exactly. Going from 40 MHz FSB to 50 MHz won't give you any magical boost. 4x40 is clearly the better option.

retro-net.de/blog.html

Reply 15 of 39, by Bige4u

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Just go socket7 with a p200 and be done with it?

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Reply 16 of 39, by amadeus777999

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I have mine(ADZ) booting at 200 and working at 180(tested thoroughly without any error in DOS and Windows).
It runs at 180 with just 3.6V and no voltage enables it to run with 200 as it does not even boot at anything over 4.5V. On the contrary one intel DX4 runs at slightly below 5V@133 without complaints(albeit I would not let it run in anything but a test system).
So... 200 is pushing it severly and you would have to freeze cool the cpu. It would be awesome to finally see a cpu running at such speed... the ultimate 486 for demanding "vintage" games.

Reply 17 of 39, by rmay635703

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What I find unfortunate is that AMD was dislexic on the 5x86,
They needed it to stay alive but didn’t want to improve it or invest anything into clocks higher than the 5x86 150mhz because they were focused on selling more expensive k5’s that nobody wanted.

They could have focused on making the 5x86 more computationally efficient with a better floating point, higher clocks and skipped k5 going straight to k6 and the world would have been all the better for it.
The k5 would have made a better 486 chip than a pentium but all is well in hindsight

Reply 18 of 39, by swaaye

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My guess would be K5 was seen as a necessity because Socket 5 was hot stuff. The platform was much improved and K5 had the potential to beat Intel. It's just unfortunate that they apparently didn't have the resources to get K5 working in a timely manner. It's doubtful they knew it would be so difficult. Am5x86 seems like a no-brainer to me. Low risk product. It turned out better than developing something like Cx5x86, a chip with more potential but too many compatibility issues and bugs to get there. Engineers that could have been helping make 6x86 better.

As for the ultimate DOS CPU.... that depends on a lot of factors. Many games will benefit from a much faster CPU, like a Pentium 3. Some people like K6+ CPUs because you can reconfigure their multipliers in software for a very wide range of speed characteristics.

Reply 19 of 39, by The Serpent Rider

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and skipped k5 going straight to k6

They didn't skip anything. To begin with, K6 was not their design.

Last edited by The Serpent Rider on 2019-07-12, 13:17. Edited 1 time in total.