BEAR 486 box boot problems

[TortoiseWrath]

So... I ended up with a BEAR Computer Systems i486DX box from 1994-ish (is all I know about it). When I first got it, it booted to its UNIX installation just fine. I played around with it for a bit, then shoved it off into my pile.

I came back to it now, about a year and a half later, and got one long, three short beeps. Because this indicated a RAM, GPU, or motherboard failure, I started with the best-case scenario and removed both of its RAM sticks. This resulted in a different beep code, so I eliminated the possibility of a motherboard failure.

I performed the usual RAM diagnostic process (try different configurations until it works), and found what I presume to be a bad stick. With one of the sticks in the first RAM slot, I didn't receive a beep code (nor did I receive a POST beep ) and I heard some HDD activity - what sounded like the normal boot process.

However, I didn't get anything on my monitor - not even a "video mode not supported" message. I assume that this is either a problem with the 32-bit EISA GPU itself, or with the fact that I tried plugging it into a 1080p LCD. Any ideas? I don't have an older monitor available for testing at the moment, but I can obtain one relatively easily, so I'm going to try that.

UPDATE: It would seem that each of the sticks was 4MB, and that booting with only one stick may not work on an old system - I found that these 72-pin SIMMs sometimes had to be installed in pairs.

 

[C12Friedman]

Just so I'm understanding this, you are running (or attempting to run) an older version of UNIX and not MSDOS on this dinosaur...
My only suggestion is to check your interrupts - been a (little) while but I seem to recall having to physically set those (PnP not supported). I'm assuming you can access BIOS. Wow, talk about a blast from the past...

 

[TortoiseWrath]

I cannot access the BIOS setup screen, as I'm not getting any graphics, which is the problem.

I'm only trying to run UNIX because that's what was on it when I got it; I'm hoping to install MS-DOS 5.0 and Windows 3.1 on it if I can ever get it to boot.

I determined that the two SIMMs were both 4MB Toshiba 72-pin 70ns x32 FPM modules. Wikipedia says that two SIMMs were required to fill a bank with the Pentium, but only one was required with the 486 series; despite this, could only having the one SIMM installed be part of my problem?

 

[C12Friedman]

Just want you to know, you're really taxing my memory here and I'm finding woefully little online to help jostle it some... if I haven't gotten back (or someone else with a better memory than mine), bump this in a day or two please.

 

[TortoiseWrath]

Yep, that's pretty much the same problem I'm having here. No worries.

 

[lourendo]

has this pc been powered on in a while? did you use a variAC to ramp up your PSU? if not, you may have some leaky caps and might have a bad psu. its been so long and i was so young to really remember my days with I486's to really give an adequate analysis. i just know old PSU'S can fail without a proper variAC ramp up. also caps can go bad throughout time. if i can remember properly, low voltage can give you erratic POST codes. just a thought. good luck!

 

[TortoiseWrath]

The PC powered on fine about a year ago, when last I tested it. No variac was used; I'm pretty sure that the variac trick works only on linear power supplies, which were phased out in 1977-1981 in favor of switching power supplies.

I'll think about testing the PSU (though I have other things to do ), but it doesn't seem like a PSU problem to me, unless only the +12V rail went out; the PSU fan spins up and the hard drives spin up, I just don't have any graphics (I think) from the EISA card.

It occured to me that I may just need to wait longer for the graphics, but I'm pretty sure that it should have the graphics running before any hard drive access, so that BIOS messages could be displayed.

My Macintosh SE is still ticking... I'll just use that for a while.

 

[lourendo]

The PC powered on fine about a year ago, when last I tested it. No variac was used; I'm pretty sure that the variac trick works only on linear power supplies, which were phased out in 1977-1981 in favor of switching power supplies.

I'll think about testing the PSU (though I have other things to do ), but it doesn't seem like a PSU problem to me, unless only the +12V rail went out; the PSU fan spins up and the hard drives spin up, I just don't have any graphics (I think) from the EISA card.

It occured to me that I may just need to wait longer for the graphics, but I'm pretty sure that it should have the graphics running before any hard drive access, so that BIOS messages could be displayed.

My Macintosh SE is still ticking... I'll just use that for a while.

good call, too much time working with old stereo equipment and radios i guess.

 

[TortoiseWrath]

I'm going to be in a less rural area in a few days, so I'll see if I can pick up some RAM or a graphics card there.