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486 RTC Chip Problem? (MB-8433UUD-A Ver 2)

H

High_Treason

Experienced Member
Joined
Apr 4, 2013
Messages
219
Location
England
Now I'm in a bad mood. I bought a 486 motherboard (with a load of other stuff) and it arrived yesterday, it's this one, but there is a problem.

Every time the POST screen appears, no matter what, I get
CMOS Checksum Error - Defaults loaded
CMOS Batter Failure

I'm willing to bet the lithium battery in the ODIN OEC12C887A has probably gone and died on me... I have heard of them failing but it's never happened to me (I probably have five or more boards in service that use these packages and they all work) but that would explain the battery failure message. What I want to know is whether the inability to store values is also normal for this? I know if I turn the machine off it won't hold them but when the coin or barrel batteries fail the system will still hold the values for as long as it has power. With this one, I can go into the CMOS Setup, change things (or not) and press F10, Y and return to POST where the message comes up again and the defaults are loaded again by the system. Also, if this is just down to chip failure and nothing more serious, I can replace this with a Dallas 12887A right? Or a regular Dallas 12887? I can't find any of these ODIN's around, at least, not as cheap as the Dallas.

I'd usually just try replacing it but I'm broke right now and don't want to end up spending money if it's likely to be a problem elsewhere. Everything else seems to work, I can boot from a floppy and poke things around. I bought the board for a Cyrix 5x86 that I have yet to retrive from the post office, right now it's running an Am486DX4-100 which is identical to another machine I have, same Cache, even using the same RAM (Out of a Korg :D) but I lose about 36% performance against the other one according to NSSI (And Topbench), which I am hoping is down to badly configured CMOS settings and not the board. Coincidentally, the battery is failing in the other one now, though that's a coin battery and I have replacements for those on hand.

Ugh, this build has gone horribly since step 1 :(
 
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All the boards I tried do hold the CMOS data for as long as the PC is powered on, even if the battery has failed. It's weird. Are the Dallas and CMOS jumpers set to normal operation and internal/external battery jumper set to "internal"? Also, is the DALLAS chip removable or soldered? If it is soldered, maybe the best option is the usage of an external battery.
 
Jumpers are correct, I don't have JP42 as that is for the coin battery versions of the board, JP12 has only two pins on this version which should be open.

Annoyingly this one is the only one I have that is not socketed and as it's between JP12 and JP13 and the sides are surrounded by a PCI and ISA slot I'll have to take it off the board to work on it as there is no external battery and the pins on these ICs are not connected to the motherboard; They are folded up in the package and connected to an internal battery as far as I know... I am tempted to try taking it out and cutting it open to connect an external battery as others have done, the board isn't useable as it is so there'd be no loss if I broke it I suppose. As I would install a socket, I could then order a replacement package if it worked.
 
For anyone following this, though I doubt if anyone around here gives a damn about anything I do, I'm going to have to write it off as a dead board, a trace came with the old chip - I know where it goes so I wasn't too upset on that - but worst of all, the socket I put in it's place literally will not solder to the board, some pins will but most of them won't, I've just wasted a couple of hours for nothing. I wouldn't say I'd wasted £50 though, after shipping, the cards, CPU and RAM that came with it would probably amount to that and I am sure they'll find amachine to live in as they work fine, can never have enough Cache RAM handy anyway and given what else I saw the board probably had something else wrong with it. On the downside I now have a PAS-PLUS and a Cyrix 5x86 that I have no use for as I'll be lucky to find another board that supports it.

Edit: A minor edit as I implied I was swearing, figured I'd remove that despite my anger as I was angry at the failure and not the reader... This has gone worse than any build ever.
 
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Sorry to hear it didn't work out... :-( I know how frustrating it can be to put lots of time into something only to have it end a failure. On the flip side, think of the things you have learned. It's all the little problems over the years that I've run into that have taught me most of the obscure weird stuff that I know about computers...

Wesley
 
I try to learn from everything... What I have learned is that my mistrust of Biostar probably wasn't misplaced though to be fair, it lasted 18 years and I suspect the journey accross the atlantic might have been what upset it. I shall also practice the battery hack with the removed chip so I know what I'm doing when others fail. As I am nearing completion of the collection, I was beginning to think things were going too well.

As luck would have it, I literally got paid again just hours ago. I desperately need a new workstation, so I'm mad for forking out on this, but I decided to kill two birds with one stone, seeing as I had considered getting an AMD 5x86 to mess with but couldn't find an excuse. In short I bought this and ordered a heatsink, I still plan on putting the ST branded Cyrix in there, but at least now I've got an excuse to mess with AMDs offering too. Also, no silly RTC as this one uses coin batteries.

I was surprised at how hard it was to take that chip off, I've replaced chips on boards before, that solder literally wouldn't melt proerly (probably contributed to damaging the trace) nor will my solder bind to it, I even hit it with a 100W gun. Usually I've only had that in old PSUs. My fingers are burnt and my solder sucker is considerably more singed looking.

Hopefully it goes well this time, I'll make an appearence on the forum somewhere with it regardless. That leaves me with two CPUs remaining on my want list; an IDT and a Rise, plus a single sound card (Ensoniq SoundScape) as I own everything else I care about now aside from a particular GeForce 4 which is easy to find. I have one issue, which is that I had planned to get this 586 finished in time for my next YouTube appearence, I'll have to find something else to mess with, perhaps it's time I finished work on the VIA C3.

Oh, I just noticed the BIOS date on that one I just ordered, 10/10/94, it might have it's birthday somewhere between Bulgaria and here, and it's only 4 days (and 4 years) after mine, though for some reason I always miswrote mine as 10/10, maybe it's a good omen!
 
Looks like a nice board! At one point along the line, I ran a 5x86 CPU for a while. I like those old and slightly odd things! I've been working through my pile of 486-ish systems, seeing what is good and what isn't removing batteries...hoping the ones that leaked haven't ruined the motherboard (batting 0 on that hope), etc. Found an Acer system with a 486 motherboard...don't recall, but it might have had a 5x86 chip on it...but it has PCI, ISA, and one VLB slot. Pretty cool...

Good luck in your continuing search!

Wesley
 
I'll make an appearence on the forum somewhere with it regardless
Click to expand...

Well, for those curious as to how I got on, new board arrived, seemed to work fine. Built my own case (A hideous orange thing, don't ask) and everything went smoothly, until it broke a CF Card... Cheap second hand ones, I put a new one in... Oh, I was sent the wrong CF adaptor btw. I got the OS installed, seemed to be going fine, next thing I know there's Divide overflow, KB INterface Error (Never seen that before), finnicky about the ram, kept shutting the power supply off. Now it powers on, but there is nothing. No beep, no picture, no heat in the CPU. At a complete loss, shame really, according to topbench I was keeping up with Pentium 200's (I still doubt the accuracy of such a program, but it seems to be the bible around here) but I never got to try and games or demos, I literally got as far as finishing the 95 install, shut it off to do something else, wrote ethernet drivers to a floppy, bolted the side panel on and powered back up to find the problems out of hand. Can't get it running and I have no desire to mess with another one. 486 was my favorite gen, this has tainted it a little. Oh, I think it took an S3 Virge with it as well as my floppy disk.

At least I own the cpus now, guess all I need now is my IDT and a Rise and I'm done.
 
Sound advice, but this was my intial thought. Voltages are nominal, tested with PSU under load. Tested with another PSU, same result. As far as I am concerned, dead mobo with no salvageable parts, sadly it seems it will join the Biostar and about ten K7 systems on the trash pile of broken dreams. To make matters worse, I built my case to the size of this board and it's unusually small, my only hope is that a Socket 7 PC Partner I was never going to use will fit as I suspect that'll provide a good base for a shoddy WinChip or something. That was the last board around that supported these 5x86 chips, save for a rather shoddy PCChips one.

Before anyone blames the case, it is plastic and wood and the board sat on 2CM wooden standoffs, so nothing conductive there. I'm still rather upset, I had to cut that perspex stuff for it and I hate working with that, I nearly sliced my finger off. Oh, and don't get me started on the K7's I mentioned, that was years ago but I'm still peeved about those.

As a final thought, it's late and I could be missing something obvious, maybe I forgot to flip a jumper or something. I will give it one last chance tomorrow, after which it is consigned to a life in the cupboard as I hate throwing things out. I might try chucking a 33MHz 5V CPU in as those settings bypass some of the circuitry. If that gives life I may be able to track down the problem, could be a dead voltreg or something.
 
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The reset button wasn't working properly, but it doesn't appear to be that.

System starts up with a 486DX33 just fine, I can run the others at 5V (though I don't want to for obvious reasons) so I am beginning to suspect the C3420 power transistor as that is either on or bypassed (3V or 5V) and it doesn't get warm yet given that it has a heatsink (which was rather loose) I suspect it would if anything was going on in there. I can get one (or an equivalent) cheap enough. It's a three pin component at the edge of the board with nice thick traces so it should be easy to replace, this board seems better built than the Biostar anyway so hopefully there won't be any of the problems which that one presented.
 
This will be my final update to the thread. The machine is alive and well after fitting a 2SC3420 (With larger heatsink and paste) but performance is really lacking. I think I'll keep it for spares and the novelty of the 586 processors, but as it is I can outperform it on a 100MHz Am486 so it's just wasting space and none of the RAM I have besides the rubbish that came with it will work in the board I think I'll dismantle it.

I might sell it at a later time for little more than the price of postage, can't make my mind up yet.

Could be useful if I want a slower 486...
 
The Biostar MB8433-UUD that you have was one of the better made PCI-based 486 motherboards available with a UMC chipset. There is tonnes of literature available on this board. v3.1 and some v3.0 boards came with a socketed RTC module. For those with a soldered RTC module, you need only desolder the RTC with a solder sucker and an appropriate soldering tip. For the more stubborn pins, I use around 430 - 440 deg. C for a brief moment to suck out the solder. Do not do any prying with the RTC - ensure that all solder has been sucked out.

Once you've desoldered the RTC, solder on a socket and buy a new Dallas 12887 RTC. It should last you up to 20 years if you buy a new 12887.

This motherboard is particularly fussy with needing a working RTC battery, otherwise the settings will not saved upon CMOS saving. What you can do is use MODBIN to save your desired default CMOS settings, and reflash the BIOS on your board with this saved version. This way you can keep using your old RTC if you like, but you'll still be annoyed with the dead battery warning and not be able to save the date.

This board is also fairly straight-forward to add a 3.0 - 4.0 voltage trimmer to. I've also had success in modifying the board to work with 1024KB cache.
 
Firstly I wouldn't say that this board is "lacking performance" at all. Secondly I think it is silly to build a 486 system for SPEED. Just go with a Pentium if you need that :)

Picture of the board with ODIN RTC removed:

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When I received the board it came with a ODIN RTC with a dead battery. For some reason this board does NOT store BIOS settings, even when powered on. The board would hang at this screen:

jvhxMkQh.png


Removing the cache chips solved the problem

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but replacing the ODIN RTC with a DALLAS from eBay fixed the issue of the board not remembering BIOS settings. I wanted to put a socket it, but couldn't wait and just soldered in a DALLAS from eBay :) I had to de-solder a jumper which was blocking the DALLAS from fitting. I believe it's the clear CMOS jumper.

Tzt5Zrqh.jpg


I proceeded to set the time and load the BIOS defaults and the board hung again at the same point as before:

jvhxMkQh.png


In turns out I had to set the option "EDO DRAM installe option" to "Enabled". I didn't change any other settings, I never do as I value stability more than speed tuning :)

Currently the board is fitted with 256KB 15ns Cache, an IntelDX4, 16MB EDO memory (LGS branding on 8 chips) with 60ns. Video card is a PCI S3 Trio64V+ with 2MB and for storage there is a floppy emulator and a 2GB CF card with a single 500MB FAT16 partition.

Here some images to check out!

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