Repairing a tricky L2 cache issue of a SOYO 4SAW2 486 Motherboard 

Good job finding that ACLK issue. It would certainly be one of the more difficult things to figure out.

Lucky that the datasheet is available for that chipset really. Not often the case with 486-era hardware.

Nice repair / debugging video :) Thank you for the mention! I measured really fast in circuit the C37 with an LCR meter at 50pf. Probably not a very accurate measurement, but I think you are ok there with 100pf.

I really appreciate your tenacity in repairing hardware like this and I wish I had soldering skills like you do!

My 486 hangs with the same cache issue, you have inspired me to take another look thanks

Nice troubleshooting clip, I do find these interesting!

Fantastic video. I learned a lot from this repair. Thank you for uploading.

Thank you for the amazing videos. Makes me want to get my Pii system up and running again.

Once again, here is another excellent video, interesting and very well documented. You deserve way more views.

Nice work indeed! Great video

Superb work in getting the board semi up and running. Amazing job as always.

AWESOME video!

Great repair!

Great video, subbed! I have to say I was surprised at your decision to replace the unknown capacitor with a random value - although as others have said, the video would've been less interesting if it weren't for this :). I encountered a very similar situations, with an ATC-1425 board from which someone harvested a few SMDs, mostly in the VRM and PLL areas, and in the case of the PLL since the capacitors weren't decoupling but part of a RC network of some sorts I chose to leave their spots empty after seeing the board worked just fine without them. I just wish I had your diagnosing skills...

Very good job !

incredible this board has isa, vlb, and pci

Great work on this one; solving issue after issue to get a winning result in the end. Appreciate the explanations, helping improve the electrical knowledge and debug process!

mega awesome repair. i see you as an Einstein, not kidding :)

Excellent video

Very informative video. Thanks for sharing :)

Well done. Mighty impressive

Hi Sir! Amazing video! Fantastic repair job!

great vid, thanks

very enjoyaable to watch

I had an interesting issue with Matsonic M601 motherboard. On DX2 -66 it ran with 512KB cache just fine, but when I tried a DX5-133, it gave no signs of life. On some forum they suggested reducing the amount of cache to 256KB. I took half of the dip chips out, and DX5 booted up fine. I was never given an explanation of why that was happening. It was strange that a newer CPU would refuse cache and the old one didn't.

I have exacly same problem with U-board ST1A and tried everything other than looking for signals etc...

A M A Z I NG!

Measured in circuit value of C37 of 80-85pf, using Uni-T UT61E multimeter.

Are there any metal parts under the AT or PS2 connectors? Just as you didn't insulate the repaired traces. But great video! Loved the tracing of the cache pins.

Great Joob 👍

Which Epsom programmer are you using

ASUS PVI-486SP3 has capacitor C34 right next to the chipset itself. Unfortunately i was unable to measure it in-circuit. :(

Some of the boards from SOYO. We’re actually quite good, but those were pentium boards. They even did a half decent pentium 2 board too.

Why solder a ps/2 connector for AT cases that don’t have an opening there? Or have they?

Not sure if you know this, but using a dishwasher with no soap is the lazy way to clean boards. Rinse in isoproply/metho if you're cheap after and it'll look new.

i have never had any good luck with 486 and PCI slots..

The L2 cache seemed to be nothing earlier, a 128 kb or 512 kb had no difference. If there was no cache or was cache, it made a difference. With Win 7 activated windows, Sec Essentials regularly opened the tray, asking for the Win dvd to be inserted. Windows does it yearly, even offline. The use of the cache later appeared to be true, at 50% load, 1 Ghz the windows is as fast, as at 2.1 Ghz full load. My theory is, that the Cpu uses 0-5% during startup, because the chipset uses the cache for everything, instead of asking the cpu to work. My cpu is only loaded when I play, watch video or streaming. The cache is important to keep the fan at minimum rpm, especially when someone takes a laptop into an office, the high speed fan is disturbing. For 486, the cache is able to switch the cpu to passive cooling, and the fan may not be needed. Cache frees up the cpu from loading it, the chipset uses it. Similar to the difference between the pio, and ultra DMA mode, but that’s about the hdd. Inactive, unregistered windows won’t use the cache, and the cpu will heat up. Win 9x has a reg trick, you can no longer register it. Receive any A4 fax successfully.

Yeah you would get a PS/2 cable on a back plate in the box with those back in the day.

[2:36] Duke???

Replacing a capacitor with some random value... what could possibly go wrong. That's why it's worth checking if it's at least a filter cap or not, so you won't have to replace cache, desolder/replace 7408, check the board with oscilloscope and going through chipset datasheet. On the other side - the video won't be so interesting then!

If you are removing the solder mask and the joints are good, there is no need to tin coat the traces. What you should do is cover the tracks with mask. What you didn't do. In other words, you did what you shouldn't and you didn't do what you should do. You should NEVER remove the battery charging circuit. Use a compatible battery. Please be a good technician and do things correctly.