I think you can just flash the latest BIOS to the revision 1.8 board with Uniflash or the provided Asus flash utility.

With the revision 1.22 board you will likely have to flash a new suitable FLASH chip with an external flasher or "hotflash" the new suitable chip as the older FLASH chip isn't supported by the later BIOS versions (you can flash the new BIOS to the old chip but countless bugs renders the board more or less useless with that combination of BIOS and FLASH chip).

I would also try the motherboard you are going to use with another 3V CPU just to make sure the 3V/5V CPU auto detection works as it should... Not that I ever have heard of it not working on the PVI-486SP3 but well the Cyrix 5x86-133 is kind of valuble...

Jumper settings for the Cyrix 5x86 133 (4X) and other CPUs not listed in TH99 can be found here.

http://gboeger.de/Computer/Asus_PVI486SP3/pvisp3-cpu.html

The rest of the jumper settings.

http://stason.org/TULARC/pc/motherboards/A/AS … PVI-486SP3.html

I ran this motherboard in a comparison, however, I cannot remember if I used a Cyrix 5x86 or Am5x86. Performance comparison of 486 motherboards with VLB-only, PCI-only, and PCI+VLB
I checked my Excel file, and I also didn't specify which CPU I used. This is not typical of me.

Anyway, the board mentioned should have a jumper for 3.6 V. You will want to use the 3.6 V setting. The scanned manual is the one I used for my board. I recommend you get your motherboard setup and working with a Cyrix 5x86 at 2x33 MHz and at 3.6 V. Once you confirmed that works, swap in the Cyrix 5x86-133 with heatsink/fan. The manual has a jumper diagram for Cyrix Cx5x86 (M1sc). Follow this. Then set the voltage to 3.6 V with JP7.

Do you have a top and bottom photo of the CPU? Do you know if it comes from one of the CPU-World collectors? 2-weeks salary isn't very specific. What kind of dough we talking? $200 or $2000?

Skyscraper wrote:

Jumper settings for the Cyrix 5x86 133 (4X) and other CPUs not listed in TH99 can be found here.

http://gboeger.de/Computer/Asus_PVI486SP3/pvisp3-cpu.html

Thanks. That was the only setting I couldn't find.

feipoa wrote:

I ran this motherboard in a comparison, however, I cannot remember if I used a Cyrix 5x86 or Am5x86. Performance comparison of 486 motherboards with VLB-only, PCI-only, and PCI+VLB

One of the boards already has an AMD 5x86 in it, so I have the setting for that.

feipoa wrote:

Anyway, the board mentioned should have a jumper for 3.6 V. You will want to use the 3.6 V setting. The scanned manual is the one I used for my board. I recommend you get your motherboard setup and working with a Cyrix 5x86 at 2x33 MHz and at 3.6 V. Once you confirmed that works, swap in the Cyrix 5x86-133 with heatsink/fan. The manual has a jumper diagram for Cyrix Cx5x86 (M1sc). Follow this. Then set the voltage to 3.6 V with JP7.

Cool, thanks.

feipoa wrote:

Do you have a top and bottom photo of the CPU? Do you know if it comes from one of the CPU-World collectors? 2-weeks salary isn't very specific. What kind of dough we talking? $200 or $2000?

I don't have photos yet, but will photograph it tomorrow in daylight. I'm testing it for isa-d on CPU-World. I think you saw the guy offering $500 for it. 2 weeks wage is an arbitrary figure I plucked out of thin air to indicate that it isn't cheap 😀

I don't think $500 is enough... Try to get more... The Cyrix 5x86-133 is as rare as they get...

If the CPU is in good working condition with good pins you (r friend) will have no issues getting that CPU sold but beware of scammers... Paypal gift or bank transfer (I would prefer the latter) if the buyer isn't well known with good reputation.

Skyscraper wrote:

I don't think $500 is enough... Try to get more... The Cyrix 5x86-133 is as rare as they get...

If the CPU is in good working condition with good pins you (r friend) will have no issues getting that CPU sold but beware of scammers... Paypal gift or bank transfer if the buyer isn't well known with good reputation.

It's an old-timer on the CPU-World forums that is selling it. This price makes it almost as expensive as a C4004 😀 Most buyers and sellers on there only use Paypal gift option.

OK, looks like this offering is from http://www.cpu-world.com/forum/viewtopic.php?t=30315
So the exchange is a Cyrix 5x86-133/4x for a Cyrix 5x86-120/4x + $500. The Cyrix 5x86-120/4x is also fairly rare, but of limited value for people on Vogons because we want to run at 4x33 MHz. I don't know what the trade value is of the 120/4x, perhaps $70-120? It can, thus, be inferred that market value for the 133/4x is $600 USD.

EDIT: Actually, another vogons buyer was willing to pay $1000+ for this chip, so it is realistic that market value is between $600 and $1000.

Which tests will you be running to ensure that the 133/4x works?

Well as I notice the would be buyer is a Vogons member I change my mind. $500 + a Cyrix 5x86 120 seems fair. 😁

🤣

debs, do you have a Voodoo2 or Voodoo3 PCI card? To stress the CPU, I often run GLQuake and Quake II in OpenGL mode. Quake II is even better at catching crashes for marginally stable configurations. If you don't have these graphics cards, then you can also let DOS Quake run in loop for an hour and at least ensure that Windows 9x or NT4 will boot.

In DOS, I recommend setting FP_FAST to enabled (1), BTB_EN to enabled (1), MEM_BYP to enabled (1), and LSSER to disabled (0). These are the most important settings you want to ensure work at 133 MHz. If these settings don't work, the CPU is of limited advantage compared to a 120 in which these settings do work. Fortunately, I haven't found a 133 MHz CPU in which these settings didn't work. I have tested four to-date. There is one minor exception - I used to run a Cyrix 5x86-133/4x in a system that was on 24/7 which acted as a small HTTP server. I also used it for email. I was getting a BSOD after 2-5 days of uptime. After about a month of testing register settings, I determined that disabling DTE_E solved the BSOD's in NT4.

If you are testing in Windows, you must disable BTB_EN (0). Disabled is the default value. I normally enable RSTK and LOOP in Windows when BTB is disabled.

I've written some guidelines here, Register settings for various CPUs and Cyrix 5x86 Register Enhancements Revealed

feipoa wrote:

debs, do you have a Voodoo2 or Voodoo3 PCI card? To stress the CPU, I often run GLQuake and Quake II in OpenGL mode. Quake II is even better at catching crashes for marginally stable configurations. If you don't have these graphics cards, then you can also let DOS Quake run in loop for an hour and at least ensure that Windows 9x or NT4 will boot.

I recently sold all my 3dfx cards, mostly on eBay. When I next have significant money to reinvest, I will replace some of them.

In DOS, I recommend setting FP_FAST to enabled (1), BTB_EN to enabled (1), MEM_BYP to enabled (1), and LSSER to disabled (0). These are the most important settings you want to ensure work at 133 MHz. If these settings don't work, the CPU is of limited advantage compared to a 120 in which these settings do work. Fortunately, I haven't found a 133 MHz CPU in which these settings didn't work. I have tested four to-date. There is one minor exception - I used to run a Cyrix 5x86-133/4x in a system that was on 24/7 which acted as a small HTTP server. I also used it for email. I was getting a BSOD after 2-5 days of uptime. After about a month of testing register settings, I determined that disabling DTE_E solved the BSOD's in NT4.

If you are testing in Windows, you must disable BTB_EN (0). Disabled is the default value. I normally enable RSTK and LOOP in Windows when BTB is disabled.

I won't be testing all the registers or benchmarking extensively on this chip, as if I blow it up I can't afford to pay for it. You have given me a lot to think about though when I have appropriate CPUs in my collection.

I've written some guidelines here, Register settings for various CPUs and Cyrix 5x86 Register Enhancements Revealed

Wow, that is a lot of info to absorb. I will probably write my own drivers to set the registers when I start testing my own collection, but your info will make it a lot easier to set things correctly. I have downloaded some useful utilities, but can't (yet) find setmul.

Just going to boot to DOS then?

SetMul is here: SetMul - Multiplier control for VIA C3 / AMD K6+7+8 Mobile / Cyrix 5x86

I will install Win 95 (not sure which versions I have, I need to check) and do some benching, I just won't push it as hard as if it were mine, and I won't overclock it. I plan to test under DOS and Windows. I have my own CPUID app for DOS which will read the DIRs.

I don't think anyone would be daring enough to overclock a Cyrix 5x86-133/4x chip. I ran an IBM 5x86c at 150 MHz in DOS for a few hours before it stopped working entirely, so I think 133 MHz is a fairly realistic ceiling for these chips.

I would suggest at least turning on FP_FAST & disabling LSSER and running the free demo version of Quake's timedemo in DOS. A single test should only take a minute or two. If it were me buying the chip, I'd want to ensure that those features at least worked before dishing out $500 and if they didn't work, I wouldn't want the chip. Cyrix disabled the more interesting features to make the chips compatible with older hardware, e.g. those which were not Cyrix 5x86-aware. I've only tested the Cyrix 5x86 with LSSER disabled with a PCI graphics card, so I'm not sure if there are issues with VLB graphics cards.

Any update on the test so far? 😀

I'll be building the system on Saturday or Sunday. I'm not the quickest person when it comes to getting stuff done. Just waiting for a small enough drive to arrive in the mail. All the IDE HDD I have found in my stash are greater than 8.4 GB, so I am guessing are too big for a 486 system. The only flash drives I have are 256 MB, so too small for Win 95. Just ordered an adapter to use a 2.5" drive if I have to.

I used to install Win95a from diskette back in the 90's and after installation it consumed around 50 MB, depending on which options you select.

Cool, I can just use a flash drive for now in that case.