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Reply 20 of 47, by Intel486dx33

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ShovelKnight wrote on 2020-03-31, 21:06:

I doubt you would be able to achieve this level of performance (or lack thereof) with a Pentium-class CPU.

But for all means try something that runs at 50 MHz FSB. You can actually jumper your Pentium 100 (66x1.5) to run at 75 MHz (50x1.5). My feeling is that it would run roughly as fast as 386 SX-33.

Hey, that worked. I now have the AMD K6-100 running at 75mhz.
90mhz is the slowest K6 supported . Do you think there is a problem running it at 75mhz ?

Disabling the caches dropped it down to a 386 at least.

What is a score of 7 in speedsys ?
What is a score of 56 in Topbench ?

I know that a 286@20mhz will score a 50 in topbench.

Some posted that a 386dx@40 scores a 9.2 in Speedsys test.

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Reply 21 of 47, by ShovelKnight

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If it runs at this speed, there should be no issues.

I see you have an early version of the K5 which is slower than the later versions. Still, I think its ALU is faster than the Pentium ALU at the same speed. So if you exchange your K5 for a Pentium, you might get lower integer results (which is what actually counts for very old games) and faster FPU results.

Reply 24 of 47, by vitalm

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Intel486dx33 wrote on 2020-03-31, 22:48:

Yeah, I am going to put the Pentium on this Intel Motherboard and the K6 on the Via chipset motherboard.
Then I will compare performance at various speeds.

... and the next step will be a Slot 1 board with an unlocked Pentium II, SetMul for disabling L1/L2, and hardware throttling to 1/8 (Intel chipset) or 1/16 (VIA chipset) by fdapm.com or throttle.exe. There is a lot of info about unlocked Klamath and Deschutes here on vogons. Even if your motherboard has no multiplier change option in its BIOS, unlocked Klamath can be set to 5x multiplier by jumpers to actually get 2x multi with L2 enabled. Then choose FSB from the 50...150 MHz range and run some software rendered Carmageddon, Redguard, etc. in 640x480 mode. Just do not use ASUS P3B-F - both throttle.exe and fdapm.com have zero effect on it.

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Reply 25 of 47, by Intel486dx33

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I just purchased some Pentium CPU’s but I don’t know when they will arrive because the post office is closed because of the Virus.
I want to test with the
Pentium-75
Pentium-100
Pentium-120
Pentium-150
Pentium-175
Pentium-200
Pentium-233

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Reply 26 of 47, by pentiumspeed

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Which Pentium 100 that can go to 1X multiplier? I'd love to play with socket 5 or 7 at 1x using a Pentium CPU.

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Reply 27 of 47, by cyclone3d

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ShovelKnight wrote on 2020-03-31, 21:06:

I doubt you would be able to achieve this level of performance (or lack thereof) with a Pentium-class CPU.

But for all means try something that runs at 50 MHz FSB. You can actually jumper your Pentium 100 (66x1.5) to run at 75 MHz (50x1.5). My feeling is that it would run roughly as fast as 386 SX-33.

If you have a motherboard with a 40Mhz Feb setting and a Pentium Overdrive chip, you should be able to force a 40Mhz CPU speed by removing the integrated fan. It it supposed to put it into 1x failsafe mode.

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Reply 29 of 47, by clueless1

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If you want to go down to 286 speeds, you will have to stick with a 486 and combine turbo with disabling caches. If you want to run the fastest games, you'll want a P233MMX or a K6-2. The P233MMX will slow down to fast 386/slow 486 levels, no more. If you replace the 233MMX with a P75, you can get it a bit slower, maybe down to a slow 386. If you stick to VGA resolutions, the P75 will run most high-end games (like System Shock, Cybermage, USNF, Screamer, etc) decently. But these games will run better on something like a P133. Personally, I use POD200MMX and it runs everything from Wing Commander to Duke3d at decent framerates. Quake still needs to run in 320x200 to be playable. I did swap a P75 in when I played Wizardry 6 because text was going by too fast even when the POD200 had all caches disabled. There's no such ultimate DOS system that will run 286 games and late DOS games in hi res.

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Reply 30 of 47, by infiniteclouds

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If you want maximum speed tweaking flexibility nothing is going to beat the VIA C3 CPUs -- specifically the Ezra/Ezra-T chips. You'll want to use them in a compatible slotket adapter in a slot 1 motherboard for the most flexibility. These can do everything an Pentium MMX 233 can do on the low end of downclocking and can exceed a K6 in terms of speed on the high end.

Reply 31 of 47, by kolderman

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They barely might keep up with a k6. I push an ezra 1ghz to 1.2ghz and it just manages to play q2 and unreal gold at acceptable frame rates. They slow down well, but they start to struggle towards the end of 1998....consider a high end p3 (same socket) will easily get you through 2001 with gpu upgrades.

Reply 32 of 47, by infiniteclouds

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My Ezra-T at 1.2 matches my K6 III+ at 500mhz in performance. The Nehemiahs can definitely exceed them (which is what I meant). You're quite right that when you are coming to end of '98 on you want more power and the beauty of the Ezra (in a slotket) is that you can swap in a Pentium 3 quite easily (without changing thermal paste). Of course you're going to need that power for 98+ but the thread was about DOS and C3s are much better for this than either a Pentium or K6.

Reply 34 of 47, by appiah4

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I went with a high speed Cyrix 6x86MX/mII for this and don't regret it.

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Reply 36 of 47, by appiah4

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ShovelKnight wrote on 2020-04-06, 10:21:
appiah4 wrote on 2020-04-06, 10:11:

I went with a high speed Cyrix 6x86MX/mII for this and don't regret it.

How does it scale with caches off?

L2 off gets me to around 486 DX40-50 levels, L1+L2 off gets me to around 386DX40 levels. That about covers all speed steps I give a crap about.

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Reply 37 of 47, by ShovelKnight

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appiah4 wrote on 2020-04-06, 12:14:

L2 off gets me to around 486 DX40-50 levels, L1+L2 off gets me to around 386DX40 levels. That about covers all speed steps I give a crap about.

Thank you, it does look very promising.

Reply 38 of 47, by jheronimus

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I'm actually messing with Pentium MMX slowdown myself. My system is using an Intel TC430HX motherboard — AFAIK, the last Intel motherboard that uses AMI BIOS instead of Phoenix and as such has sort of a "turbo" function.

JKcplhKm.jpg

Here's its normal operation in System Information 8.0 benchmark:

HYU1LBnm.jpg

And here it is with turbo on

ZRVvqJhm.jpg

The manual states that the turbo mode should be similar to "25 MHz AT system". So it's somewhere between a fast 286 and mid386. Not sure what method of slowdown it is, though. But even if it's just turning caches off, it's nice to be able to do that with shortcuts. And that's before I started messing with setmul.

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Reply 39 of 47, by Intel486dx33

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The Intel Chipset motherboard I am using has a Turbo button but it does not seem to work. So I just disable cache in bios and with SetMul utility.
With the AMD K5-100 running at 75mhz I have been able to slow down the CPU to fast 286 levels. Maybe 40mhz. I am not sure.
But it is definitely slower than a 386@33mhz.