Here's someone who removed the heatsink,
http://www.cpushack.com/chippics/IBM/5x86/

It says,

IBM 5x86C

IBM26 5x86-3v3100GF

What is the status on your Cyrix 5x86-120 repair process. It is pretty much the fastest 486-class CPU you can get your hands on these days. However if you mainly want to diddle daddle around in a word processor, an AMD X5-160 might be sufficient.

Ive emailed another seller that sold a gainbery kit recently and he said he would list more for sale, he has'nt, he had 100 & 120 versions id try to buy another 120 if it popped up, this guy only wants for $20 or $25 for each cpu.

I can't do much without a new upgrade package or new mainboard, it would probably cost me $50 to repair the voltage regulator on the mainboard, im always on the lookout for a better mainboard, this one has a sis 496/497 chipset.

Which motherboard? Photo?

Lucky star 486e

http://motherboards.mbarron.net/models/486pci/ls486e.htm

It wont work with voltage set to 4 or 3.3, obviously 5 volts will kill the cyrix and and its a damn shame the voltage regulator adapter thing was broken otherwise id be running it right now, so I either fix it or buy another gainbery kit and use the adapter.

Not a bad looking board, but lacks a PS/2 port. SiS chipsets seem to work with Voodoo Banshee's and above (compared to UMC chipsetted 486s).

Did you check with a volt meter to see what voltage actually arises out of the 3V and 4V setting? Seems strange that a PCI 486 board wouldn't have a 3.3 or 3.45 V setting.

Your Cyrix 5x86-120 wouldn't turn on with 4 V? Mine did, but I wouldn't run it for long there.

You can modify the voltage regulator on your motherboard to output 3.6 V (what the Cyrix 5x86-120 wants). For the 3 V or 4 V jumper setting, find the resistor that controls V.adjust on the regulator. I wrote up on how to do this somewhere on the forum. With some half decent soldering skills and access to an electronics store (or newark.com if you want to pay shipping) that sells precision resistors, you can modify the output voltage yourself. Surface mount resistors aren't too difficult to hand solder in, however, you can also solder on wire leads and solder on a fat resistor (if you don't mind your board looking ghetto).

I've modded my board to run my Cyrix 5x86-133 at 3.70 V. And yes, to that precision according to my volt meter.

Recieved the other cpu, it was in shrink wrap and when I opened the package the cpu was pressed into the plastic with no other packing material, some of the pins were bent but nothing serious, the cpu did go in the cpu socket without any trouble, its obvious that these gainbery upgrades arent packed with much care at the factory, this confirms to me that the original cpu was damaged in transit.

Unfortunately my mainboard appears to be dead, before I tried the latest cpu I put in a 486DX2 chip and could'nt get it to work, removed some ram and it booted, tried another 486 chip and would'nt turn on, trying different sets/combinations of ram would boot once in a while but then freeze. Big shame as the board was rock solid, I might try another power supply but I doubt its the problem.

For some reason the board has come to life?!

Ive run some benchmarks without any tweaks.

Speedsys - 55.1 / memory speed - 34mb/s, pathetic, my 386 is double that
3dBench 66.6
Pcpbench 7.3

CHKCPU says the cpu is 100.1mhz in 3x mode, I assume thats not the real mhz as the startup screen and speedsys both say its a 120mhz cyrix.

Where do I get the software to run the cyrix enhancements?

These are my computer specs

Cyrix 5x86 120
LS486-E
256k cache
128meg EDO ram, (4x32), I'll try some other ram.
1.2gig hard disk, onboard controller
cd-rom 50x
sound blaster 16 (non pnp)
16meg 3dfx Voodoo 3 pci

I did manage to run quake 2 and half life, not playable though.

Changed these pci settings in bios

master arbitration control (weak) - STRONG
cpu-pci mem post write buffer (disable) ENABLE
cpu-pci memory burst write (disable) ENABLE
pci master burst write (disable) ENABLE

3dbench 76.6fps
pcpbench 8.3fps

nice little increase, then played with memory settings

3dbench 83.3fps
pcpbench 8.5fps
speedsys memory - 36meg

I thought I'd try leaving one stick of 32meg in the system, so that all the memory could be cached?? Did'nt change a thing still around 36mb bandwidth, this is a 32meg 60ns edo double sided stick

then tried 2 16meg 60ns, single sided edo, same result,
70ns double sided double sided (does'nt say fpm or edo), same result

Surely something is seriously wrong unless speedsys is'nt reporting the memory bandwidth correctly, this is for version 4.78

Now we're getting somewhere....

Level 2 cache changed from write back to write through

Speedsys - 100mb/s
3dbench - SLOWER - 76fps
pcpbench FASTER - 10fps

Tried putting the cpu into write through mode but that resulted in slower results.

cachechk tells me that I have a 106mhz cpu? So, where do I get those cyrix 5x86 utilitys?

edit: The cpu is a 05h, stepping 0 revision 5

What BIOS cache wait states and memory wait states are you using?

I get 100 MB/s for system memory bandwidth using Speedsys 4.78 on a Cyrix 5x86-100. 121 MB/s for a Cyrix 5x86-120. Please refer to the tables in the Ultimate 486 Benchmark Comparison (PDF version) for a rough idea of what speeds each 486 processor should yield with a particular benchmark test.

What FSB-to-PCI multiplier are you using in the BIOS? Note that if you are using a 40 MHz bus and are using a 1:1 FSB-to-PCI multiplier setting, your heavily graphiced 3D video results will be slightly higher than those returned for, a Cyrix 5x86-120 that is reported in the Ultimate 486 Benchmark Comparison.

Is your L2 cache in Write-back or write-through mode? The effect of all RAM being cached isn't really witnessed in DOS-based programs since most users have 256 KB cache and 32 MB RAM and most DOS benchmarks use less than 32 MB RAM. Windows handles RAM differently, so you're more likely to noticed decreased benchmark scores in a Windows environment.

Your pcpBench score is fantastic. It is surprising that your 3Dbench score doesn't quite keep up with it. Your Voodoo3 might be partial to some of PCPbench's code. I wonder if Voodoo3 drivers and a 486 will work in Windows 9X/NT/W2K?

As for your cachechk speed report, cachechk7 will show 106 MHz, cachechk4 will show 120 MHz for a CYrix 5x86-120.

Okay, these are my current bios settings for chipset features

ISA Bus Clock - 1/4 PCI
LBD# Sample Point - End of T2

Cache write cycle - 2CCLK
cache burst read cycle - 1 CCLK
l2 cache/dram cycle ws - 2CCLK

Dram ras to cas delay - 2CCLK
Dram write cycle - 0WS
Dram write cas pulse - 1CCLK
dram cas precharge time 1CCLK
Dram ras to ma delay - 2 CCLK
dram speed - fastest
dram slow refresh - disable
cpu internal cache - write back

l2 cache policy - write through
l2 cache tag bits - 8 bits

And as above these are the pci chipset featres

master arbitration control (weak) - STRONG
cpu-pci mem post write buffer (disable) ENABLE
cpu-pci memory burst write (disable) ENABLE
pci master burst write (disable) ENABLE

I was able to find the cyrix enhancements and I have been successful in increasing benchmark scores, I turned all these features on

RSTK_EN
BTB_EN
LOOP_EN
LSSER
USE_WBAK
WT1
BWRT
LINBRST
FP_FAST
MEM_BYP
DTE_EN

Now with speedsys

memory bandwidth - 133.77MB/S
CPU - 66.30

3D Bench v1.0 - 90.9fps ,
PCPbench - 10.4fps - would lock up unless rstk_en=off

In windows 98 SE BTB_EN=off as it locks the system straight away, testing 3dfx Quake 2 in 640X480 gives

9.4fps with sound, 9.8fps without,

Quake 1.06 timedemo 2, 320x200 no sound
no cyrix enhancements - 13.9fps
with enhancements - 14.4fps

Bit dissapointed with the Quake scores but everything else looks good, am I supposed to run UNIVBE or any other dos video driver?

These BIOS settings look very 386-AMI era to me. What BIOS is on this board?
These look to be in a slightly different format to what I am used to:

Cache write cycle - 2 CCLK
Cache burst read cycle - 1 CCLK
L2 cache/dram cycle ws - 2 CCLK

Are these the smallest possible numbers?

DRAM SLOW REFRESH set to ENABLE is the optimal setting (if your RAM supports it. Mine does).

L2 CACHE POLICY - WRITE-BACK is the optimal setting (w/256KB cache, you can cache 32 MB of yoiur RAM in Write-back mode. This is optimal for DOS. If you are using Windows and have 64 MB RAM, use write-through mode so that you can cache up to 64 MB).

As noted in the U4BC, LSSER set to OFF is the optimal setting. Your other settings are fine, however it is unlikely you can leave BTB enabled in Windows for very long. Your best chance of using BTB_EN in Windows is if you turn off LOOP_EN and RSTK_EN. It may still hang eventually. The preferred option to using BTB_EN in Windows is with a Stepping 1, Revision 3 Cyrix 5x86.

Your speedsys memory bandwidth is fantastic. Faster than any 486 board and stock Cyrix I've tested by an extra 13 MB/s, but I didn't test any of my Cyrix 120/133's with BTB enabled. Is this the source of your gain? I typically do not consider benchmark results with unstable settings to be valid. EDIT: I did infact get 134 MB/s with a Cyrix 5x86-120 using the 60 MHz x 2 FSB setting.

For comparison with the U4BC, what do you get for Quake 1.06 timedemo1, 320x200, full screen, console off, no sound? I should think around 16-17 fps.

What Windows version did you test with?

What result does cachechk give you for L1, L2, Memory, and RAM access read/write time?

Is the Speedsys memory bandwidth reporting accurate? On my 486 VL/EISA board it reports 245MB/sec. Even though L1, L2 and main RAM scores come nowhere near this.

Something certainly doesn't look right with your memory bandwidth, but your L1/L2/RAM look like a typical Cyrix 5x86-120's. If you plopped in a EISA SCSI card and a EISA 10/100 LAN card, that would be a pretty unique retro system. Actually, why not go all the way with 128 MB RAM, you have the L2 to back it up.

Your SpeedSys reminds me of this very odd result with a Cyrix 486, here,
Crazy speed 486, comparable to a Pentium III

In this post, my Cyrix 486's Speedsys performance matched that of a PIII. SpeedSys certainly hasn't hammered out all their bugs with odd combinations of hardware.

I don't want to hijack this thread, so if you want you can ask additional questions here:

My Ultimate VL/EISA 486

I'm actually already running with wide SCSI and 100mbps ethernet on the EISA bus. Unfortunately I need to get a faster drive. I just have some shitty old 2gb seagate barracuda at the moment.

I also already have 128mb installed. But for some reason only 64mb is reported by speedsys and dos. Perhaps I need an updated himem.sys?

Fair enough, I have replied there.

I am using windows 98SE and that version of dos, I tried to install dos 6.22 but the system hangs when it trys to boot from the boot disk.

If I put L2 cache in write back mode the bandwidth sinks to 34mb/s, thats why its in write through mode, according to speedsys.

@dirkmirk

Does your motherboard have undocumented 60/66 MHz FSB settings? If so, you can run that IBM 5x86C-100HF at 133 MHz.

I dont think so, I've tried every jumper setting combination that corresponds to the fsb jumper and I cant even get 50mhz, have you tried running your cyrix at 150mhz? I'll probably keep an eye out and collect 5x86 boards for the rest of my days 🤣, this board is good for stock settings but not much else it seems.

I have not extensively tested a Cyrix 5x86 at 150 MHz. That would make for a hell of a 486. I did some initial 150 MHz tests some time ago, but they were not conclusive. A monster-sized fan would definately be recommended. I'll likely re-visit this at some point.

What would really be cool for overclocking is a socket 3 interposer with 0-5V variable voltage and discrete-variable frequency adjustment.