Well, I somehow got the Bios to recognize the A: drive properly, but now the one good HDD that I had started making some loud clicking and scratching noises. 🙁
Maybe click'o'death. One step forward, two steps back. Well, enough complaining... at least there's still a good chance I can get one of the machines running.
Now to my question... is there a safe way to test if the HDD is really dead? I'm a lil' bit wary of plugging it into the 486 again.

Is there any chance the PSU might be defective??
Wouldn't hurt to try another. Or try swapping Molex connectors around.

Ok I plugged in a different molex cable, moved the drive away from the PSU itself (I guess it slid around a little), and reset BIOS. Result: Now BIOS can see the drive again but refuses to allow me to boot up win95 boot disk... came up with "Disk I/O error, replace the disk, and then press any key". Where I was able to at least use a boot floppy for an old version of System Commander to get to it's main menu before, it now boots to BIOS every time and then says "missing operating system" when I put the disk back in. I'll keep trying to see if I can jimmy it into working.
I love this site.

Ok the system has some trouble seeing the hdd right now, but it works sporatically and I tried to launch an installation for MSDOS 6.22. It came up with an error reading/writing to the A: drive after making it to the main installation screen... I feel like I'm almost there.

Edit: The drive is back to making those scratching sounds and isn't visible in BIOS anymore. Next step is to try one of my other PSUs I guess.

it could also be a failing hdd
you should try another one also

I had black screen with ASUS TXP4 when:
1. using PicoPSU/ATX (this MB has an ATX connector in addition to AT power)
2. using AT PSU#1 without load (no HDD/CDROM/FDD connected).

When I tried my second AT PSU (#2) the motherboard worked OK, and it also worked OK when I connected load to the AT PSU#1.
After I replaced 9 capacitors on the motherboard it started working with whatever powers source I plugged into it.

P.S. Next day I burned the i430SB though, but it's another story.

Welcome to Vogons! 😁
Thanks for the advice, I now have a new AT PSU being shipped to my house just incase my current ones are dying. 😁

I used Tenma digital multimeter to check PSU voltages and they were something like +-4.3V/+-10.5V for bad AT PSU and about +-4.7V/+-11.3V for "good" one (without load if I remember correctly. The values differ when there are real HDDs/CDROM connected instead of just CF card in CF2IDE adapter).

At the moment, I'm playing with Netier NetXpress XL1000 and Advantech PCM-9370 and PCM-9375 boards together with Skynet SNP-9541 PSU instead of "real" AT systems. Maybe I'll be able to get -5V from Skynet's -12V using negative voltage VRM, but I'm noob in electronics so this may take long time to happen

Personally I don't like either voltages. The second ones are very low imo, the 1st one is just pretty BAD.

If the voltage is off by anything more than 10% its is "bad" by standard definition. (12v can be off by up to 1.2v, 5v by .5v, etc)

That being said, I wont use any supply that is more than 5% off.

I cant seem to find a "brand" of AT power supplies that I can trust, however if you dont mind atx -> at converters then I would look on ebay for TTGI or Superflower power supplies. More specifically the "4-fan" model.

http://cgi.ebay.com/SUPER-FLOWER-SF-450TS-GOL … =item335dcb8e41

I picked up that one for a song. They are an EXCELLENT power supply for any pre-p4 system. They have MASSIVE 5v rails and are easily adapted to an AT power supply. Granted they come in funky colors, but its nothing a can of spray paint cant solve if i really cared.

luckybob wrote:

If the voltage is off by anything more than 10% its is "bad" by standard definition. (12v can be off by up to 1.2v, 5v by .5v, […]
Show full quote

If the voltage is off by anything more than 10% its is "bad" by standard definition. (12v can be off by up to 1.2v, 5v by .5v, etc)

That being said, I wont use any supply that is more than 5% off.

I cant seem to find a "brand" of AT power supplies that I can trust, however if you dont mind atx -> at converters then I would look on ebay for TTGI or Superflower power supplies. More specifically the "4-fan" model.

http://cgi.ebay.com/SUPER-FLOWER-SF-450TS-GOL … =item335dcb8e41

I picked up that one for a song. They are an EXCELLENT power supply for any pre-p4 system. They have MASSIVE 5v rails and are easily adapted to an AT power supply. Granted they come in funky colors, but its nothing a can of spray paint cant solve if i really cared.

I've done quite a bit of reading on PSU's. Jonnyguru comes to mind 😀

Like all other hardware, there is no perfect brand.
I personally prefer FSP for 2 reasons:
*They are always of better build quality
*They were used a LOT here in The Netherlands (including by a couple oem's) so are relatively easy to find second hand (=cheap).

I know there are countless other good manufacturers, but those I very rarely find second hand and the new ones are too expensive for my taste (even the old models).

I feel that this post needed some conclusion, so I just wanted to say that I've solved all the problems that I had with the soyo 4saw2 and it's now running and installing windows 95c (just to prove to me that it actually works).
Thanks to everyone for their time, patience and advice.
The problems that I fixed were:
replaced the PSU with a stable one
replaced the ram with fully compatible sticks
cleaned the board and all parts
changed the HDD with a stable one
changed the cache chips.

nemesis wrote:

I feel that this post needed some conclusion, so I just wanted to say that I've solved all the problems that I had with the soyo […]
Show full quote

I feel that this post needed some conclusion, so I just wanted to say that I've solved all the problems that I had with the soyo 4saw2 and it's now running and installing windows 95c (just to prove to me that it actually works).
Thanks to everyone for their time, patience and advice.
The problems that I fixed were:
replaced the PSU with a stable one
replaced the ram with fully compatible sticks
cleaned the board and all parts
changed the HDD with a stable one
changed the cache chips.

Thanks for giving us the happy ending.

Lol, apparently you fixed it by replacing basically everything 😜