swaaye wrote:

:happyhappy: Oh I know how that goes. One thing leads to another and soon there are 10 packages on the way. […]
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feipoa wrote:

@swaaye
I've always been intrigued by the MediaGX, but am afraid it would open a can of worms with my Cyrix 5x86 obsession. It could end up being a money pit of doom.

😁 Oh I know how that goes. One thing leads to another and soon there are 10 packages on the way.

sliderider wrote:

Relative to Pentium, how fast is a 200mhz 486? About a Pentium 100? If that's as fast as it goes, wouldn't a Pentium Overdrive 83 have more overclock potential on this motherboard since it's almost to 100mhz to start with?

Yeah a Pentium tends to be about twice as fast at the same clock rate unless you are using the FPU a lot or have an app with significant Pentium optimizations. In some cases Pentium may be about 3x faster per clock because of optimizations in addition to its vastly faster platform.

How will the 2 compare in speed when not using Pentium optimized code? I remember that in the beginning the Pentium 60 was about as fast as a DX4-100 when the Pentium was brand new. That would make the Pentium roughly 50% faster when using non-optimized code?

Extra Cyrix 5x86-120's... If this wasn't my daily machine, I'd say yes, but alas I need the backup proc. for this system in case of failure. The exception to this would be if you wanted to trade a working Cyrix 5x86-133 for a 5x86-120. 😀

I understand your situation. Unfortunately I have only two Cx5x86 100MHz (one with anodised cooler and second without it). If I had Cx5x86 133Hz I would not need Cx5x86 120MHz. I think so. (;

Yes, to change the regulated voltage, i.e. for the 4.0V jumper, you need to find the surface mount resistor that corresponds to Vadj. of the regulator (for that jumper setting only). Vreg., for example, can be measured on PGA pins C4 and B4.

I really like such specialized information! However in my opinion these old CPU's are very tolerant - they should safely withstand 4V so this modification is not necessary as for me.

Regards! (:

I really like such specialized information! However in my opinion these old CPU's are very tolerant - they should safely withstand 4V so this modification is not necessary as for me.

That may be true in the short-term, but for such a rare processor, it is a much safer bet to pamper it. Plus it will run cooler at 3.7V vs. 4.0V (it already runs a bit on the warm side at 3.7V).

EDIT: The Cyrix 5x86 manual lists the voltage tolerance at +-0.15 volts. I believe the basis of this is largely from thermal considerations.

feipoa wrote:

I really like such specialized information! However in my opinion these old CPU's are very tolerant - they should safely withstand 4V so this modification is not necessary as for me.

That may be true in the short-term, but for such a rare processor, it is a much safer bet to pamper it. Plus it will run cooler at 3.7V vs. 4.0V (it already runs a bit on the warm side at 3.7V).

EDIT: The Cyrix 5x86 manual lists the voltage tolerance at +-0.15 volts. I believe the basis of this is largely from thermal considerations.

Yeah, you're right. I became careless after my CPU overclocking experiments. This is partly due to the fact that I haven't damaged any CPU yet. On the other hand I used to do only quick tests and everything could change if I start to use those parts constantly. As you mentioned above factory settings are safest (but I still think that 4V is fully secure for socket 3 CPUs).

Regards! (:

I have just received Biostar MB-8433UUD-A VER:2! This motherboard is really small but looks very high-end. Finally I have 1:2/3 FSB to PCI divider! Also I'm very surprised because it has chipset supporting EDO memory: UM8881F 9552-ETS (bios is dated to 12/05/95).

Here you are some screens:

Great! 😀 I'm really glad you've got this mobo. I am very interested in learning more about this mobo's BIOS options. I have added my current options to your BIOS set up screen photo. I am not sure if all of my options are correctly set up for "maximum/fastest performance". I would be very interested to learn which ones might not be the best option to select, for "maximum/fastest performance".

I am wondering something. What's this please? It looks like a small wire, on one of the SIMM slots. It's a zoomed image taken from your photo of the revision 2 mobo.

Thank You rg100! You are amazing! [: The small thing that you have found is a piece of grass! ^^ I cleaned a little bit this motherboard but I skipped this blade. I don't know what is the history of this motherboard but when I opened the package it looked like it was lying in the past few years in barn! [:

Also thank You for publication your bios settings. At first glance your bios settings looks optimally. I'll check them soon. In the first place I would like to test one of my am5x86 ADZ on this motherboard and then I will focus on bios performance optimisation.

Thank You again! (:

I have one problem - I can't find JP17 jumper! [: Is it possible that this jumper is wired permanently?

udam_u wrote:

I have one problem - I can't find JP17 jumper! [: Is it possible that this jumper is wired permanently?

Oh no! 😳 😢 That could be really bad news. That could mean that your mobo will not allow you to select certain FSB speeds. Those "disallowed" speeds could be: 20, 50, 60. If JP17 is permanently "closed", then these FSB speeds cannot be set. For 20, 50 and 60 FSB, jumper JP17 needs to be in the "open" position.

You can test this. Firstly, remove the jumper on JP15. If you set JP16 to "closed", and you use an AMD 5x86 133MHz CPU, what speed is reported? If JP17 is permanently "closed", then the speed reported on the BIOS POST screen will be 160 MHz. That's because JP16 + JP17 in the "closed" position = 40 FSB. If JP17 is permanently "open", then the speed reported on the BIOS POST screen will be 180 MHz - and you may need to increase the CPU voltage for this information to successfully appear on the screen. That's because JP16 in the "closed" position = the undocumented 60 FSB setting.

If you go to this webpage: http://stason.org/TULARC/pc/motherboards/B/BI … 486-MB-101.html And then look at the CPU speed selection table, it says: "Note: JP17 may not be present on all boards." 😢

retro games 100 wrote:

You can test this. Firstly, remove the jumper on JP15. If you set JP16 to "closed", and you use an AMD 5x86 133MHz CPU, what speed is reported? If JP17 is permanently "closed", then the speed reported on the BIOS POST screen will be 160 MHz. That's because JP16 + JP17 in the "closed" position = 40 FSB.

I'm afraid you are right! I set JP16 to "closed" and bios screen reported 160MHz. [: I'will watch pictures posted by you and sliderider to see if my motherboard contains the same chips as yours. If so I'm going to install jumper in place of wire! (:

EDIT:
Yeah - I repaired my motherboard! After this operation I set multiplier to 3x and JP16 to "closed" and bios screen reported: am5x86 180MHz! [:

Motherboard after modification:

Wow, nice! 😀

I have made quick test - my am5x86 even don't want to boot on this motherboard at 200MHz. rg100 how can I set 5V to CPU? I can't determine first pin on jp36, jp37 and jp39.
I have no more time today but I will return to test tomorrow. (:

Here ya go! 😀 Please note that I am looking for a job working as a motherboard manual writer.

Ah crap. One of mine has a wire permanently jumpered across JP17. I'll have to check the other one to see if it has it or not.

WHEW! The other one has a normal jumper there. I was getting nervous for a minute.

Would it be possible to solder in the required pins to make JP17 active or is there something else different about the boards that don't have it that would make it impossible?

Any idea what JP18 was supposed to do? Neither of mine has the pins for it but there is space for another jumper there.

retro games 100 wrote:

Here ya go! :happy: Please note that I am looking for a job working as a motherboard manual writer. […]
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Here ya go! 😀 Please note that I am looking for a job working as a motherboard manual writer.

Just don't apply for a job as an illustrator. 😜

@rg100
Thank you! Your drawing explains everything! Unfortunately my am5x86 ADZ don't want to boot at 200MHz even when set to 5V...
Currently I use small ATX power supply with ATX to AT adapter instead of AT power supply. Here is a picture of my PSU:

I think it is better than any AT PSU but maybe still not sufficient for am5x86@200Mhz on biostar mobo. MB-8433 has very small capacitors around the socket and things may go wrong when unstable 5V is applied to CPU (5V goes directly from PSU without additional voltage stabilizer). What power supply do you use?

@sliderider

Would it be possible to solder in the required pins to make JP17 active or is there something else different about the boards that don't have it that would make it impossible?

I only soldered a jumper in place of wire - that's all. (:

Re: PSU. That's very interesting. I wonder, is this problem due to the ADZ architecture, or is the PSU an important factor? Could it be a combination of the two? I wonder which issue is more pertinent, the ADZ or the PSU?

I use two PSUs for all of my testing. This is completely "over the top", but I do this in order to eliminate all uncertainty about the quality of the power supply. I use two Enermax PSUs, model number EG465P-VE. There are other good similar PSUs you can get, such as the ThermalTake 480APD. One PSU powers all of the peripherals, while the other PSU powers the mobo.

Please note that using these PSUs, I have never been able to get the ADZ to boot at 200 MHz, so it's likely that the problem is exclusively due to the ADZ. Also, I wonder if you need a "magic" ADW to get the 200 MHz speed to work successfully? I briefly tested some of my other ADWs, and I couldn't get them to work as well as my current ADW.

I use two PSUs for all of my testing. This is completely "over the top", but I do this in order to eliminate all uncertainty about the quality of the power supply. I use two Enermax PSUs, model number EG465P-VE. There are other good similar PSUs you can get, such as the ThermalTake 480APD. One PSU powers all of the peripherals, while the other PSU powers the mobo.

You are crazy man! [: I use the same PSU (EG465P-VE) as yours in my dual Athlon MP rig! On the other hand you provide perfect conditions for retro tests.

Re: PSU. That's very interesting. I wonder, is this problem due to the ADZ architecture, or is the PSU an important factor? Could it be a combination of the two? I wonder which issue is more pertinent, the ADZ or the PSU? (...)
Please note that using these PSUs, I have never been able to get the ADZ to boot at 200 MHz, so it's likely that the problem is exclusively due to the ADZ. Also, I wonder if you need a "magic" ADW to get the 200 MHz speed to work successfully? I briefly tested some of my other ADWs, and I couldn't get them to work as well as my current ADW.

It is very interesting. Probably I still haven't encountered my Holy Grall. However my most stable ADZ processor boot at 200MHz on GA-486am/s motherboard... I don't know how good are ADW because I haven't tested any yet. I wonder if your "magic ADW" would boot at 240MHz on ga-486am/s motherboard... ^^

What is the latest bios for MB-8433UUD rev. 2 and where can I find it? Thanks! [: