I'm certainly not the best to answer this, but when I was building my 98 PC I had problems where my DVD drive would stop being detected sometimes. I ended up having a faulty stick of RAM, I'd definitely try running memtest, as there is no harm in trying.

And btw nothing wrong with your English 😀

Tough!
These freeze of yours are so reproducible.
I agree with the previous poster. I have MEMTEST on a botable CD, but you will need a floppy! 😐

Usually RAM problems kicks in so fast. 15 minutes ? You're sure of this ?
Never had a problem like yours and I spend my time on old stuff.

The best way to diagnose this: narrow things (like using PCI cards - if you can use them).
Why don't you take a photo and attach it over here ? You don't even have to host the image. Very easy...

If it only occurs after some time then it might be related to heating up of components.
Can you give a bit more info regarding your setup?
What type of motherboard, what type of 486 cpu, what is the type of controller card.
My guess is you have either a bad contact somewhere when the board heats up. I have 2 motherboards here where the bios chip has a bit of corrosion on one of the legs.
I have to move the chip a bit so it keeps making contact, something similar might happen to you right now, because if you insert the isa card the motherboard flexes a bit and this might be enough to restore the contact each time again.

Take out the battery and measure it with a multimeter, then show us the number.
Seems way off, but this is my saying - Make changes when you want a change 🤣

CPU is working. Messing around with CPUs is the last thing you need.

Nvm1 wrote:

I have 2 motherboards here where the bios chip has a bit of corrosion on one of the legs.
I have to move the chip a bit so it keeps making contact, something similar might happen to you right now,

My VL4200 with VLB slots is out of order because of this! I recommend you not to use the board like that.

Nvm1 wrote:

because if you insert the isa card the motherboard flexes a bit and this might be enough to restore the contact each time again.

I lost a M919 for joint solder!
In these cases, the solution is a hot air station, isn't it?
I don't have a hot air station and for some silly reason I tossed it 😠 I regret that.
I checked the chips with a magnifying glass and solders were all good. Dunno if we can see bad joint solder this way.

Thank you for the replies.
I think that the problem is a kind of thermal expansion of some component (and making losing
contact of some pin or welding), because after 30-35 minutes none of ISA slot work. I was hoping
that the problem was on a specific component (I don't know, a kind of "ISA controller chip" or whatever)
By the way, the CMOS battery is dead. Tonight I'll try to replace it with a new one.

I not remember exactly the model of mobo or other components, but the CPU is a Intel Overdrive (486DX2/66)
with stock heatsink.

Thanks to you all, i'll keep you up-tp-date.

Frasco wrote:

Tough! These freeze of yours are so reproducible. I agree with the previous poster. I have MEMTEST on a botable CD, but you will […]
Show full quote

Tough!
These freeze of yours are so reproducible.
I agree with the previous poster. I have MEMTEST on a botable CD, but you will need a floppy! 😐
Usually RAM problems kicks in so fast. 15 minutes ? You're sure of this ?
Never had a problem like yours and I spend my time on old stuff.

Tonight i'll try with my memtest floppy.
10-15 minutes... maybe 5-6 or less (time flies when I'm working on old stuff) 😜
Thanks!

Illy76_it wrote:

Thank you for the replies. I think that the problem is a kind of thermal expansion of some component (and making losing contac […]
Show full quote

Thank you for the replies.
I think that the problem is a kind of thermal expansion of some component (and making losing
contact of some pin or welding), because after 30-35 minutes none of ISA slot work. I was hoping
that the problem was on a specific component (I don't know, a kind of "ISA controller chip" or whatever)
By the way, the CMOS battery is dead. Tonight I'll try to replace it with a new one.

You said before that you change the slot the card's in and you can get it working again.

If you just physically remove it and reinsert it into the same slot, does that also get it working again, or do you absolutely have to use a different slot each time, leaving the initial slot open for a little while for it to start working again?

kenrouholo wrote:

Illy76_it wrote:

You said before that you change the slot the card's in and you can get it working again.

If you just physically remove it and reinsert it into the same slot, does that also get it working again, or do you absolutely have to use a different slot each time, leaving the initial slot open for a little while for it to start working again?

Sometime I reinsert the card in same slot and it work again. Indeed I think myself "what? i've marked this slot as working one, why now won't work?".
The only thing I sure is: if all the components are "cold" the entire system work flawless for some minutes. After a while... little inferno! ;__;

I really want to repair that motherboard: here in Italy this kind of component are very expensive. The people think has a "holy grail of retrocomputing", when
a few years ago this "holy grail" was a piece of junk,and trow that directly in the trash. For example, a "maybe working" 486 motherboard it is sold a 70 euros (75$ I think)
and an entire 486 computer have a price over 100 euros (110$).

Thanks !

Maybe it's not relevant here, but is your PSU ok?
And is the exhaust fan of your PSU working?

Your board may have a failing buffer/line driver. The ISA slots on many of the newer 486 motherboards are driven directly by the chipset, probably because there are only 3 or so ISA slots. But older/bigger boards with up to 7 or 8 ISA slots will use octal line drivers like the 74xx244/74xx245 to drive them. If you have any 74XXX type logic devices around and between your ISA slots, you could try hitting them with freeze spray while the system is running to see if you can trigger the failure event. This would help to narrow down a faulty component...if there is one.

Illy76_it wrote:

The only thing I sure is: if all the components are "cold" the entire system work flawless for some minutes. After a while... li […]
Show full quote

The only thing I sure is: if all the components are "cold" the entire system work flawless for some minutes. After a while... little inferno! ;__;

I really want to repair that motherboard: here in Italy this kind of component are very expensive. The people think has a "holy grail of retrocomputing", when
a few years ago this "holy grail" was a piece of junk,and trow that directly in the trash. For example, a "maybe working" 486 motherboard it is sold a 70 euros (75$ I think)
and an entire 486 computer have a price over 100 euros (110$).
Thanks !

Thanks ? We like feedback 😈 I'm curious to see your results.

I hate 486s **Take it easy, I don't want to be a victim of your wrath ** for DOS gaming.
Ok. I am overreacting. There must be a lot of games requiring a 486...
Even so, I like them. My first PC was a 486DX2/66.

I don't know. I have a good feeling about retro business - Imagine the kind of money you can do with
just a small collection ? Don't toss your old stuff! (I'm such an idiot telling you this in 2017!)
Vinnie Gognitti from Max Payne was so right about his collection! 😀 great game!

Back to your problem...you said:
- The only thing I sure is: if all the components are "cold" the entire system work flawless for some minutes. After a while... little inferno! ;__;

I refined the data and I bet all my money on depleted capacitors...
* Just a long shoot. Keep doing your tests and what you have to do.
This story about components expanding is not making a lot of sense to me.
Every time I had to deal with bad contact, I had to put some extraordinary amount of pressure to reestablish connection, but I know what you guys mean by "if you insert the isa card the motherboard flexes a bit and this might be enough to restore the contact each time again. - just not too feasible. All he gotta do is not flex the motherboard during installation !?

Just my little experience. Anyways, I'll wish you the best.

Frasco wrote:

There must be a lot of games requiring a 486...

http://www.vogonswiki.com/index.php/List_of_C … sensitive_games

surely not a complete list, but some data is better than none

Here I am!
First of all, thanks to FesterBlatz for his reply (the mobo have an 74C244 controller
chip near the ISA slot), and Frasco (DO YOU HATE 486?!?!!!111!? 😁 ) but the problems are three: VGA card, VLB slot and 1 bank of RAM.
My poor video card (Trident 8200C) work only in one slot ISA, and the three VLB
slot won't work with any kind of card (8bit, 16bit or VLB). At last, I have 2 bank of RAM
totally wrecked, but HIMEM.SYS don't recognize the problem. Now I have installed only
one 8mb bank of RAM and, finally, the computer seems to work again without a problem,
except for the VGA card, which it start in color mode or B/W randomly at boot, and I feel the
chip of RAM nearly hot only after a few seconds of running. I think to buy a new one.

Well, thanks to you all and I hope to see you again on this forum. Stay tuned for some photos
of my work 😀

Thanks again, bye!

Tetrium wrote:

Maybe it's not relevant here, but is your PSU ok?
And is the exhaust fan of your PSU working?

Yes, I've tried with 3 different PSU (all working).

You're welcome. I am glad your equipment is almost 100%.
When my Trident 8900C started changing colors, it died after 6 months 😐 Terrible, isn't ? Nah

Illy76_it wrote:

(DO YOU HATE 486?!?!!!111!? 😁 )

I am looking for trouble 😈 😈 😈 Scroll the screen or menu on a 486. It is slower than Pentium and in consequence you can see tearing or I may say shaking? and it gives me stomacheache!

Then there is the Super Socket 7 project (3in1) making 486 obsolete.

But my advice: Don't listen to me. There is a lot VOGONS can teach me.
Maybe A VLB card, FASTVID and tweaks like this can make a 486 fly! I just don't have enough resources to make comprehensive tests.
Maybe I'm picking the wrong parts to play later DOS games (Doom, Duke3D, Transport Tycoon,etc..)

This is too complicated and a mix of convictions.
We are twisted with the "retro feeling". 😀

til' next time.