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The World's Fastest 486

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Reply 740 of 755, by froller

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I made some more measurements.
90mV ripple on +5V rail (measured on decoupling caps near CPU socket) hence no recapping needed.
Removing second 32MB SIMM doesn't affect FPS in Quake. Either it fits in lower 32MB or 256kB of WB cache is enough for 64MB.
These SIMMs are same model and same year but one of them is more stable @50MHz FSB than another. Looks like I'm trying to push their limit.
Board freezes right after POST @60MHz FSB no matter what SIMM I use. Probabbly I just don't have fast enough ones.
3x50 is still noticeable faster than 4x40.
4x50 doesn't start at all @+3.45V.

▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ 100%
Virus check complete. All viruses are working properly.

Reply 741 of 755, by feipoa

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When on the border of stability with very fast timings at high FSB, having only one memory module installed is preferred to two modules, irrespective of how much total RAM is installed.

If you are unable to POST at 60 MHz FSB, even with slow wait states, e.g. 2ws/2ws EDO and 3-2-3 SRAM, then try higher voltage to the CPU. I have two LSD boards and both can do 2x60 and 3x60 MHz, but it requires some trial and error. From my experience, 60 MHz needs 4 V to the CPU.

Plan your life wisely, you'll be dead before you know it.

Reply 742 of 755, by CoffeeOne

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froller wrote on 2024-03-11, 12:58:
I made some more measurements. 90mV ripple on +5V rail (measured on decoupling caps near CPU socket) hence no recapping needed. […]
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I made some more measurements.
90mV ripple on +5V rail (measured on decoupling caps near CPU socket) hence no recapping needed.
Removing second 32MB SIMM doesn't affect FPS in Quake. Either it fits in lower 32MB or 256kB of WB cache is enough for 64MB.
These SIMMs are same model and same year but one of them is more stable @50MHz FSB than another. Looks like I'm trying to push their limit.
Board freezes right after POST @60MHz FSB no matter what SIMM I use. Probabbly I just don't have fast enough ones.
3x50 is still noticeable faster than 4x40.
4x50 doesn't start at all @+3.45V.

According to your screenshot, you use WB and 8bits for TAG RAM. Yes, that is sufficient for 64MB cacheable area.
But it is not a good setting performance wise.
Therefore I suggest to use either WT (then cacheable area is 64MB)
or WB, but tag ram 7bits (then the cacheable area is only 32MB with 256kb of cache).
I assume with both settings, you get higher values. Do not forget to reduce the RAM with WB and 7 bit.
When you have managed to get better values, you can re-run the comparison between 150 and 160MHz.

Reply 743 of 755, by JonF

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pshipkov wrote on 2022-05-07, 04:25:
https://www.petershipkov.com/temp/retro_pc_images/benchmarks/486_ls-486e_rev_d_q1_200_2-1-2.png A video proof. […]
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486_ls-486e_rev_d_q1_200_2-1-2.png
A video proof.

Details in the last section of the original post explaining the upgrade from 180 to 200 MHz on air cooling.

A little bit ago I emulated the mods pioneered by pshipkov & others on this forum for the Lucky Star LS-486 Rev D. Was able to squeeze out another 0.1 fps by using a 32mb LGS simm that runs at "fastest". However, the board still has the same drawbacks as described before, such as needing a PCI 1/2 bus divider for stability.

Reply 744 of 755, by feipoa

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I have found pretty much all of these SiS 496 boards to be unreliable with the PCI at 1/2.

Plan your life wisely, you'll be dead before you know it.

Reply 745 of 755, by pshipkov

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Very cool @jonf.
Share a photo of the memory module.
32mb at "fastest" is rare, unique i would say.
I think this alone gave you the +0.1 fps.
Will update the charts for your achievement here.

@feipoa
At 3x66 1/2:1 is the only way to stability for LSD and similar boards.

retro bits and bytes

Reply 746 of 755, by feipoa

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pshipkov wrote on 2024-03-22, 22:43:

At 3x66 1/2:1 is the only way to stability for LSD and similar boards.

I can believe that. I didn't do much testing at 66 MHz because the floppy controller on LSD doesn't work at this FSB.

Otherwise, for PCI: 1/2 FSB, my notes indicate the following:

Could not use my Am5x86 QFP on interposer with PCI at 1/2. Must use ceramic PGA chip. Strange.

ISA sound would not function with PCI at 1/2. Tried several ISA sound cards. Tried two motherboards, same issue. Winamp hangs up immediately. pshipkov did not witness this issue. Since I have some DOS Quake scores with sound, I think the sound issue may have been limited to Windows 95. I don't recall.

Promise PCI IDE controller hangs up with PCI at 1/2. However, it will work if setting PCI Master Burst Read/Write to disabled. This reduces throughput by 70%. I think there was some other performance hit as well, but I forget.

Even onboard IDE not working well at 1/2 PCI. I don't recall the symptoms, and I don't recall.

I spent almost a year on this motherboard trying to get 180 MHz working well, but eventually gave up in favour of the M919.

Plan your life wisely, you'll be dead before you know it.

Reply 747 of 755, by JonF

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pshipkov wrote on 2024-03-22, 22:43:

Very cool @jonf.
Share a photo of the memory module.
32mb at "fastest" is rare, unique i would say.

Here are a couple pictures, it is a pretty nondescript module

Reply 748 of 755, by 385387386

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5x86 is really a 486 CPU? I doubt it.

Reply 749 of 755, by feipoa

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385387386 wrote on 2024-04-29, 08:21:

5x86 is really a 486 CPU? I doubt it.

haha, is this bait? Am5x86, Cx5x86, and i486 only conform to the 486 instruction set.

Plan your life wisely, you'll be dead before you know it.

Reply 750 of 755, by 385387386

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feipoa wrote on 2024-04-29, 08:31:
385387386 wrote on 2024-04-29, 08:21:

5x86 is really a 486 CPU? I doubt it.

haha, is this bait? Am5x86, Cx5x86, and i486 only conform to the 486 instruction set.

Absolutely no offensive. I curiously read from Wiki, the 5x86 seems like a derivative from Cyrix M1.

The 5x86(Cyrix) seems more like a 6th generation architecture fit in a 486 package.

Reply 751 of 755, by sysctl

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The Cyrix 5x86 incorporated some features from the Cyrix M1 (6x86), but they were disabled by default, either due to instability or to avoid product cannibalization. However, even the 6x86 was not fully compatible with the Intel Pentium and identified itself as a 486, despite being a socket 7 CPU.

There's an interesting series of videos on the Bits und Bolts YouTube channel where the host tries to play Tomb Raider with a Voodoo card. Here's the segment about Cyrix 5x86: https://www.youtube.com/watch?v=_Bj1dvtfzO0&t=624s

Reply 752 of 755, by 385387386

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sysctl wrote on 2024-04-29, 09:56:

The Cyrix 5x86 incorporated some features from the Cyrix M1 (6x86), but they were disabled by default, either due to instability or to avoid product cannibalization. However, even the 6x86 was not fully compatible with the Intel Pentium and identified itself as a 486, despite being a socket 7 CPU.

There's an interesting series of videos on the Bits und Bolts YouTube channel where the host tries to play Tomb Raider with a Voodoo card. Here's the segment about Cyrix 5x86: https://www.youtube.com/watch?v=_Bj1dvtfzO0&t=624s

Awesome, the Cyrix 5x86 performed pretty well!

Reply 753 of 755, by maxtherabbit

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feipoa wrote on 2024-03-22, 21:26:

I have found pretty much all of these SiS 496 boards to be unreliable with the PCI at 1/2.

This is commensurate with my experience as well

Reply 754 of 755, by roytam1

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Sorry to be a noob here, but I want to ask: does Cyrix/IBM 5x86 supports CPUID?

Reply 755 of 755, by Disruptor

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roytam1 wrote on 2024-05-22, 13:04:

Sorry to be a noob here, but I want to ask: does Cyrix/IBM 5x86 supports CPUID?

Yes, it does.

Just first 486's (mainly SX, DX and the first DX2's) did not support CPUID.
Some of the DX4 did not have CPUID support either (AMD 486 NV8T, V8T).
I'm not sure about SX2 and first Intel DX4 versions.

However, Cyrix' 486 do have MSRs (model specific registers) too.