Ozzuneoj wrote:

I'm not familiar at all with motherboards and CPUs from this era. These are the first boards from this era I have had in my poss […]
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I'm not familiar at all with motherboards and CPUs from this era. These are the first boards from this era I have had in my possession. These boards need a couple repairs, but if I knew more about them it'd probably help.

What kind of CPU is that? How can I tell which boards it will work in and where it goes in the socket?

Does the cache on these boards look legit?

Also, the VLB board's crystal has partially lost its markings... I just see an "8" toward the end. What speed 486DX is this board likely meant for?

The CPU came in the green board with the ZIF socket, but I don't think it was installed in the correct orientation when I got it. Stupid me, I didn't realize this until after I tried to power it on. The little (VRM?) chip near the socket, with a heatsink, smelled "hot" but didn't smoke. Dumb move on my part, but I had no idea that the chip wasn't installed correctly, or that it was even possible to put them in wrong on a Socket 3 board. I don't want to mess with it any more until I know more about them. Is something likely to be dead because of this? CPU, VRM, etc...?

Any ideas as to make\model of these boards? I found a schematic for an old 386 board I got with these, and that has helped immensely. I can't figure out what brand these are though, so I haven't found anything about them online.

Also, I removed the NiCd batteries from them. I plan to purchase a bunch of 3xAAA battery packs and use low self discharge NiMH batteries for them, as those are easy to use and should last a very very long time. Is this a good idea? I'd use a button cell, but I'm not familiar with the changes that need to be done to prevent them from being charged (ruined) by the board.

Any help is much appreciated! I'm itching to test out some VLB cards and to set up a few systems to fill the huge gap between my IBM 5150 and the Socket 7 systems I have around.

EDIT: Just realized my flash washed out the markings between the ISA slots. It says in there: ASY 01-00232-___REV___ . All of the white spaces were left blank, even the S/N:____ space.

The second board looks damaged to me (there's a burn mark on the P8/P9 <-- AT PSU ports).

That crystal is most likely 14.31818 MHz, which is sort of a base frequency for PCs 😀 The chip next to it, made by Avasem, is a PLL clock generator that converts 14.31818 MHz to other PC frequencies - see http://pdf1.alldatasheet.com/datasheet-pdf/vi … ST/AV9107C.html

bjwil1991 wrote:

Ozzuneoj wrote:

I'm not familiar at all with motherboards and CPUs from this era. These are the first boards from this era I have had in my poss […]
Show full quote

I'm not familiar at all with motherboards and CPUs from this era. These are the first boards from this era I have had in my possession. These boards need a couple repairs, but if I knew more about them it'd probably help.

What kind of CPU is that? How can I tell which boards it will work in and where it goes in the socket?

Does the cache on these boards look legit?

Also, the VLB board's crystal has partially lost its markings... I just see an "8" toward the end. What speed 486DX is this board likely meant for?

The CPU came in the green board with the ZIF socket, but I don't think it was installed in the correct orientation when I got it. Stupid me, I didn't realize this until after I tried to power it on. The little (VRM?) chip near the socket, with a heatsink, smelled "hot" but didn't smoke. Dumb move on my part, but I had no idea that the chip wasn't installed correctly, or that it was even possible to put them in wrong on a Socket 3 board. I don't want to mess with it any more until I know more about them. Is something likely to be dead because of this? CPU, VRM, etc...?

Any ideas as to make\model of these boards? I found a schematic for an old 386 board I got with these, and that has helped immensely. I can't figure out what brand these are though, so I haven't found anything about them online.

Also, I removed the NiCd batteries from them. I plan to purchase a bunch of 3xAAA battery packs and use low self discharge NiMH batteries for them, as those are easy to use and should last a very very long time. Is this a good idea? I'd use a button cell, but I'm not familiar with the changes that need to be done to prevent them from being charged (ruined) by the board.

Any help is much appreciated! I'm itching to test out some VLB cards and to set up a few systems to fill the huge gap between my IBM 5150 and the Socket 7 systems I have around.

EDIT: Just realized my flash washed out the markings between the ISA slots. It says in there: ASY 01-00232-___REV___ . All of the white spaces were left blank, even the S/N:____ space.

The second board looks damaged to me (there's a burn mark on the P8/P9 <-- AT PSU ports).

Yes, its actually a blown tantalum between the P8/P9 and the SIMM slots. When I bought the lot containing this board I thought it was fried but I was pleasantly surprised to see that it was just a tantalum scorch mark.

Welcome to 486s.

The first board is Socket 3, meaning (especially with the VRM there) it supports both 3.3v and 5v CPUs.

When installing the CPU into the Socket 3, line up the key on the CPU (it can be a dot on the corner, there may be a larger corner, or a line pointing to it underneath the CPU.) to the lone pin (here on the top left corner of the socket where the lever hooks on) on the socket. Like any ZIF socket, release the retention arm, pull it back, insert the CPU properly, and then close it.

Nearly all 486 boards are configured using jumpers, so you will have to look up what the jumper configuration on your board is for your CPU, as well as what you want the clock to run at (this is configured manually too). The speed the CPU should run at is always on the chip, normally obviously (DX4-100 is 100mhz, 33x3, DX40 is 40mhz 40x1, DX2-66 is 66mhz, 33x2).

BIOS support is usually needed, but you can often get away with using a chip that's not explicitly supported on your board by BIOS so long as the clock and voltage are correct.

ALL chips above 66mhz REQUIRE cooling. This comes in the form (usually) of a heatsink that clips directly onto the ceramic of the processor. Some can clip onto the socket, but they are normally board specific.

The second board is busted. A component (blue, forgot what it is) seems to have caught fire and torched the AT connector. You could replace it (as almost everything is through-hole here) with basic soldering/desoldering equipment, as long as you can figure out what part is was. (it appears to be identical to some next to it).

It appears to be Socket 2 style, as it lacks any obvious VRM onboard. This means only 5v CPUs, or the Pentium OverDrive, will work on it. If you wish to use newer 3.3v CPUs on the board, a VRM that sits in-between the socket and the chip is needed, but they aren't remarkably common.

This is a LIF socket (not ZIF). It stands for low insertion force and does what it says on the tin. In order to install a CPU, line up the key (as before, dot, larger corner, or line (on some CPUs)) to the corner of the socket that has the 3 missing pins, and very gently press it in. Do not force it, but it won't drop in like a ZIF socket. It's in when it reaches the bottom, there is no retention arm.

The cache is legit if you run a cache test and it says you have cache. PhilsComputerLab has a benchmark/utility disk for DOS that has what you need.

As for if anything broke, you could have fried the board, the CPU, or neither. It's hard to say unless you try it again proper, and/or with known good parts. I can't see what the CPU is, but when you try it on that board MAKE SURE THE VOLTAGE IS SET RIGHT. It won't automatically detect, you have to configure it manually as well.

Also,

Boards 1 and 2 look to have had their cmos batteries removed. If we google some identifiers on these boards we may be able to get a diagram of all the jumpers to learn a bit more about CPU support. Chances are the PCI board can run everything from the lowliest 486 on up to the AM5x86 133.
Board 2 doesn't look like it took too much damage, just replace that tantalum cap and give her a smoke test 😊 .

I can't tell what CPU you have there. Is the top covered in thermal compound or something? It should say what it is. On second glance it looks like it has a little heatsink attached, does that not just slide right off or is it glued on?

with board 1, all you'll need is some 70 pin FPM ram and a graphics card and it's good to go (aside from sound, networking, etc, etc). I see it has an integrated IDE controller (IDE and FDD headers right under the RAM).

Thanks for the tips guys! Its good to know that these are completely jumper based. I know some older systems are reliant on the clock crystal itself to determine the "speed" of the board and CPU, and I wasn't sure about 486s. I've played the Pentiums and K6-2s so, jumpers are more familiar territory. 😀

As mentioned, I removed the NiCd barrel batteries myself, since they were starting to corrode, and I plan to replace the blown blue tantalum on the brown board.

The CPU has a (mangled) heatsink on it (you can see it in the picture), and it was firmly attached so I was hoping the numbers on the bottom could be used to identify it. I just took a flat head screwdriver to it just now and was able to get the heatsink off... it thankfully wasn't glued on like some Pentiums I've come across. 😀 The CPU is an Intel DX4 100Mhz. More specifically, A80486DX4-100, &E 3Volt SX900. Apparently it is a 33x3 chip and the &E indicates it has a standard "write through" cache. It must have originally been used in the green board because the jumpers on the board are set up correctly for it (33Mhz, 3.45v) Sadly, being that its a 3V chip, I can't use it to test the other board, which is 5V only, as Ampera said.

Even with the CPU installed correctly in the green board, it doesn't work (no signal on monitor, no matter what I do with the memory or VGA cards), so I'm thinking something got toasted either before I got it or when I powered it on with the CPU installed in the wrong orientation (stupid stupid stupid). The VRM is probably really easy to replace, and that's the part that gave off that familiar "hey, that's not right" smell, without smoke. It is a TIP127 VRM, and I found a lot of 5x on eBay for $3.69. I found a thread where someone described this exact problem, so I think I can replace this and the board will be back in business. 😀

Now I really want to find a CPU to fit into that old brown board. If I have a 33Mhz 386 and various Socket 7 Pentiums, what would be the best or most useful 486 for a DOS gaming VLB-equipped PC to represent the pre-pentium 486 era? I think 66Mhz is the most common speed at this time, but I'm not sure what type to look for (DX,DX2 etc.).

Ozzuneoj wrote:

Thanks for the tips guys! Its good to know that these are completely jumper based. I know some older systems are reliant on the […]
Show full quote

Thanks for the tips guys! Its good to know that these are completely jumper based. I know some older systems are reliant on the clock crystal itself to determine the "speed" of the board and CPU, and I wasn't sure about 486s. I've played the Pentiums and K6-2s so, jumpers are more familiar territory. 😀

As mentioned, I removed the NiCd barrel batteries myself, since they were starting to corrode, and I plan to replace the blown blue tantalum on the brown board.

The CPU has a (mangled) heatsink on it (you can see it in the picture), and it was firmly attached so I was hoping the numbers on the bottom could be used to identify it. I just took a flat head screwdriver to it just now and was able to get the heatsink off... it thankfully wasn't glued on like some Pentiums I've come across. 😀 The CPU is an Intel DX4 100Mhz. More specifically, A80486DX4-100, &E 3Volt SX900. Apparently it is a 33x3 chip and the &E indicates it has a standard "write through" cache. It must have originally been used in the green board because the jumpers on the board are set up correctly for it (33Mhz, 3.45v) Sadly, being that its a 3V chip, I can't use it to test the other board, which is 5V only, as Ampera said.

Even with the CPU installed correctly in the green board, it doesn't work (no signal on monitor, no matter what I do with the memory or VGA cards), so I'm thinking something got toasted either before I got it or when I powered it on with the CPU installed in the wrong orientation (stupid stupid stupid). The VRM is probably really easy to replace, and that's the part that gave off that familiar "hey, that's not right" smell, without smoke. It is a TIP127 VRM, and I found a lot of 5x on eBay for $3.69. I found a thread where someone described this exact problem, so I think I can replace this and the board will be back in business. 😀

Now I really want to find a CPU to fit into that old brown board. If I have a 33Mhz 386 and various Socket 7 Pentiums, what would be the best or most useful 486 for a DOS gaming VLB-equipped PC to represent the pre-pentium 486 era? I think 66Mhz is the most common speed at this time, but I'm not sure what type to look for (DX,DX2 etc.).

Are you using a speaker to check for any post error beeps? (I'm not 100% sure the ALI chipset will do that, but my guess is it will), otherwise you can get POST diagnostic tester if you're willing to spend a few bucks to attempt further troubleshooting.

Have you found some documentation about these boards to find out what each of the jumpers are for and the memory setup? These boards can be very picky about your memory setup. I don't think these have been mentioned:
1. Make sure you're using FPM SIMMS as the board may not post with EDO installed. I can almost guarantee the VLB board will not work with EDO. (without knowing what board it is) If you're not sure what you have post a picture of the identifying stickers/markings on what you have for us. You can usually tell based on the numbers on each of the memory ICs.
2. They are also picky about what RAM is in what banks, for example my board has 4 72 pin SIMM slots and I'm using 16MB (2 SIMMS), if I drop in a matching set in bank 1 to bring it to 32MB (using 4 simms), it fails to post. Yet my board can take 64MB with a pair of 32mb kits. Usually a 16MB FPM 70ns kit will work in bank 0 of these boards in my experience.
3. It's not terribly uncommon for the bios to corrupt and cause these to fail post, sometimes reseating the bios rom brings good fortune. If you're willing to spend again, an EEPROM burner and a fresh bios is a godsend (if you can find the proper files).. I can't wait to get my own.
4. Try pulling the l2 cache (might require changing the jumpers) and testing the board with just the CPU and a speaker, see if it beeps, see if the CPU warms up to the touch..

I hope your replacement vrms get that PCI board going for you though.

as for the other board, the i486DX2-66 (P24) is the most celebrated, since this was the chip that started selling like hot cakes to all of the DOOM players with a few bucks to blow in Dec 1993 - early 94. AMDs version of the DX2-66 is also very popular. Cyrix I believe was a bit behind the curve, but their 5x86 model for later (3.3v)486 boards is generally well loved. Unless you need time period accuracy or care about a max time period budget, the DX2-66 makes the most sense as it will perform the best, of course reality in 92-93 was that most of us with high end computers at home had a DX-33, and paid $3,000 or so to own it 😎 ..

Personally, I enjoy the DX4-100. With a decent VLB card DOOM runs like butter and I get a really nice experience in WFW 3.11. 66 is a very nice experience, but in games like DOOM 2 it's a pinch underwhelming compared to the smooth framerates we're spoiled with today. So hopefully you get the one board fixed as well so you can try it out for yourself.

Thanks again for all the info.

Just throwing this out there, but would a set of four 486 CPUs (3x 486DX 33Mhz, 1x 486DX2 66Mhz) be a good buy at $22 shipped? I have the opportunity to get some, but I'm not sure if its worth it. They are in antistatic bags and are labeled, not just loose parts in a scrap bin.

It's a good buy. If some of them are rare, it's a great buy from collector's perspective 😀

I run an EXP-4045 Socket 3 board with 32MB of RAM, and a DX4-100 OC'd to 120mhz. I do actually somewhat recommend upping the FSB to 40mhz if possible, although my part is AMD.

DX2-66 is definitely a nice idea, maybe a DX2-80 (can always up the FSB to 40mhz) would be cool too.

Keep in mind the general tips of overclocking.

nice ISSI cache chips. thats not fake
paradigm i dont know, but i bet they are real too

there is a burn mark on the power connector, maybe someone put the cables on the wrong order?

Pabloz wrote:

nice ISSI cache chips. thats not fake
paradigm i dont know, but i bet they are real too

there is a burn mark on the power connector, maybe someone put the cables on the wrong order?

Mentioned it a few times, its a blown tantalum. 😀

Thanks for the comments on the cache. Good to know!

Ozzuneoj wrote:

Pabloz wrote:

nice ISSI cache chips. thats not fake
paradigm i dont know, but i bet they are real too

there is a burn mark on the power connector, maybe someone put the cables on the wrong order?

Mentioned it a few times, its a blown tantalum. 😀

Thanks for the comments on the cache. Good to know!

The only way to know if it's real proper is to test it.

I got a new TIP127 to replace the one that died on the green board pictured in the OP, I installed it and it actually turned out pretty decently (first chip of this type I've ever soldered). The board still doesn't POST, but at least the TIP127 didn't fry itself this time.

As it turns out, I only have EDO RAM in 72pin SIMMs, but this post at VOGONS shows a board running the same chipset with EDO:
A Tale of Two 486 Motherboards (ALi vs SIS)

I also haven't found the front panel pinouts for this board so I don't have a speaker connected yet.

Any help finding the pinouts for the board or suggestions as to what could be happening would be appreciated!

The only distinct markings on the board are at the top edge and say PCI48AF-3.00.

EDIT: Derp, nevermind, I had found it already, its the other one I haven't been able to find documentation for.

http://stason.org/TULARC/pc/motherboards/T/TM … AF-VER-3-0.html

Using this information, I've got a speaker connected. When there is no RAM inserted I get one long repeating beep: beeeep....... beeeep....... beeeep
With one or two 8MB sticks of EDO inserted, I get no beeps and no display with either an ISA or PCI VGA card.

I've checked all of the jumpers on the board and they all seem to be correct for this CPU and the amount of cache installed.

I'll keep trying things, but so far, I'm not sure what to think.

Also worth mentioning that when I take out the CPU and RAM I do not get a beep code for missing memory, so at the very least the CPU is doing something when it is installed.

I've tried three different types of RAM in several different configurations, but all are EDO RAM. Not sure what else to do with what I have. I might have to put this one on the back burner until some Fast Page 72pin SIMMs fall into my lap.

The last time something like this happened it was just a video problem and required that I switch a monochrome\color jumper on the board but this board is much later and has no such settings. Hopefully the BIOS isn't shot. How would I know if that were the cause? 🙁

EDIT: Thanks to the misfortune of another Vogoner last year who could not find their BIOS for a similar TMC 486 board, I was able to find 3 BIOS files for mine. 😄

http://web.archive.org/web/19980128202027/htt … 80/PCI48AFb.htm

I'm not sure which is the latest version, but the "PCI48AFA.BIN" has the latest file date of March 27th 1996 (the others are from December and September of 1995).

I don't have a chip programmer for these sadly... is there some way I can use some old piece of hardware that takes a BIOS chip as a ROM programmer? 😀

You can try a network card in conjunction with the uniflash utility.

Ozzuneoj wrote:

I don't have a chip programmer for these sadly... is there some way I can use some old piece of hardware that takes a BIOS chip as a ROM programmer? 😀

Hmm never thought about that. Later (pentium) boards were the first that I'm aware of to allow bios flashing. If you're really nutty you could try to boot one, pull the bios and drop in a blank right before you start flashing, but god only knows what will happen 🤣 .. or maybe a NIC random ISA graphics card, but I have no idea how what software is out there to do this. I'm curious too so I'll search a bit.

Glad you got some headway going on that board with the replaced cap. Not sure where you are in the world but I recently purchased for around $8 USD a 32MB kit of 60NS FPM ram.. seller has them listed for "apple" but they worked no problem in my system. I'm pretty sure the support for EDO is going to come down to the bios in the particular board that member posted, and I vaguely recall an option on some boards to enable EDO support (chicken and egg??).. So there is still some hope that FPM will solve your problem, especially since based on your description of beep codes it sounds like it's getting stuck at RAM. I'm guessing if you go with just the CPU and RAM and no add-in cards you'll still have no beeps. No VGA or a VGA bios error usually will result in a beep code (i.e. 1 long 3 short on many). It's an affordable gamble.

Beyond this you are going to need to invest in an ISA POST analyzer and potentially the EEPROM burner to rule out a corrupt bios, and it may just come back to realizing you needed FPM all along 😎

I get no beeps when RAM is inserted. The only time I get beeps is when the CPU is installed without RAM.

I have tons of boards to play with so I'm planning to try a hot swap program for a BIOS chip, just to test. I read about it last night and it sounds fairly simple. I checked all of my really old network cards and modems that use 32pin ROM chips and it doesn't look like any have the A17 pin connected which is needed for flashing. I'll experiment with it today if I can. Fighting a nasty head cold right now. -_-

Ozzuneoj wrote:

I get no beeps when RAM is inserted. The only time I get beeps is when the CPU is installed without RAM.

I have tons of boards to play with so I'm planning to try a hot swap program for a BIOS chip, just to test. I read about it last night and it sounds fairly simple. I checked all of my really old network cards and modems that use 32pin ROM chips and it doesn't look like any have the A17 pin connected which is needed for flashing. I'll experiment with it today if I can. Fighting a nasty head cold right now. -_-

Sometimes that happens, that's why I said I'm guessing whether the video card plugged in or not it still wont beep --> it's probably hanging up at RAM during post and not progressing on to video. Usually bad or no video on these boards will result in beeps. That's just my experience from building my own socket 3 setup.. your mileage may vary.

Let us know if you have any luck. I have a few boards with fried bios ROMs and I've been far too cheap to invest in an EEPROM burner to fix em, would be awesome if I could do it cheaply 😒

Head colds are going around.. I was in bed for almost 2 weeks in November with one.. Now I'm avoiding all humans until spring 🤣