Sphere478 wrote on 2022-10-12, 17:37:

What voltage are you getting on the pins that I had on the last version? […]
Show full quote

What voltage are you getting on the pins that I had on the last version?

Last version had no ground taps

Had 3.3v taps and 3.3/5v taps.

We removed the 3.3/5v taps because it was assumed that those would probably be 5v anyway. And it would just be a pointless feature.

Did you bridge the 3.3vsb tap?

Had not bridged the 3.3vsb tap - I was assuming that was WOL related. I soldered all of the thruholes for 3.3v and what I was assuming was grounds and grounded to the motherboard chassis. I was getting around 3.3v I think. I'm going to go look at it again shortly.

checked pinouts vs diagrams and it's all good with regard to grounds and 3.3v sources. soldered up VSB and no change to my outputs, but i'm going to test these cards on another machine real quick before I go back to the board on this.

Tried a different board, DFI socket 7 with I think a 430tx chipset. Mod is successful. So it didn't work on my UMC8881F chipset 486 board, but I'm going to try that one again. So the PCB works Sphere478 😀

W00t! :p

It may be that there are other issues preventing the card from working on such a old mobo. Pci spec difference maybe.

Sphere478 wrote on 2022-10-13, 21:17:

W00t! :p

It may be that there are other issues preventing the card from working on such a old mobo. Pci spec difference maybe.

More than likely. Earlier in this thread someone mentions that they are somewhat iffy as they actually stick closer to spec 🤣. I have a ALi chipset 486 board coming that will also be used to test. If anyone wants one of these PCBs for testing let me know, it would be helpful. It’s 5 minutes of soldering maybe.

Guess what I noticed today... found a 56K softmodem, the kind of thing that's otherwise useless to most of us these days, had a spot for a 3.3V regulator and a jumper to turn on and off the onboard 3.3V reg. Looked like it would be big enough to do a couple of amps, looked like if it didn't already backfeed it's 3.3V it could easily be encouraged to do so. Not a huge amount of watts available, but might be enough to run one other card off. Unfortunately, although the PCB was optioned for it, this one does not have the components in place, and a lot of passives missing, so not real good for a test.

However, this does mean that somewhere in your tote full of useless winmodems you might find one with a 3.3V regulator on and it might come in handy for supplying another card... whether you park it next door and crosswire the 3.3V underneath, on top, or just grab the datasheet and desolder the part and plumb it in somewhere useful.

What would happen if you plugged a card that backfed 3.3V into a motherboard that already supplied it?

Depends... if your motherboard is at 3.4 volts, nothing much, if your card reg is at 3.4 and your motherboard at 3.2 then 0.2V is backfeeding and something hefty like a GPU might potentially pull enough to damage the card.

One situation that might be more prone to damage a 3.3V reg card that's backfeeding is when you have a board with an AT and ATX connector, where the 3.3V will probably be hooked up to the ATX, but if you are using the AT power, unpowered. In that case you might unknowingly maybe have something in there with it's own 3.3V that makes it look like 3.3V is available, but it's all from that card, so more than minor loads on it will likely burn out the reg. Having said that though, I believe most dual power socket boards were late enough that motherboard 3.3V reg was standard for AT/PCI boards, so most of them should have some 3.3 with AT power.

Most mobos without 3.3v it seems don’t even connect those pins to other slots

Kahenraz wrote on 2022-10-15, 03:13:

What would happen if you plugged a card that backfed 3.3V into a motherboard that already supplied it?

It should be fine. Sparing overloading conserns. From actually using more than can be made.

Does anyone see any improvements to be made?

Does this version seem okay? All good to release to the masses?

Kahenraz wrote on 2022-10-15, 03:13:

What would happen if you plugged a card that backfed 3.3V into a motherboard that already supplied it?

Dang I'm going to take a look at that.

I think the rev is good. But, I've got some more testing to do. I'd recommend putting a fuse inline if you're going to pull directly from an ATX power supply like I did. I'm not sure what the spec is for the slot is, but it wouldn't be a hefty one for sure. save some heartache.

Fuse seems unnecessary. A current draw from all those pins large enough to hurt something should also trip the psu protection. Daisy chaining the adapters should be pretty good. For more even current though, a specific purpose pcb could be made like I did for the freeway mobos seen earlier in the thread.

In any case, if a fuse is wanted, buy a axial glass fuse and solder inline. 😀

Sphere478 wrote on 2022-10-17, 00:29:

Fuse seems unnecessary. A current draw from all those pins large enough to hurt something should also trip the psu protection. Daisy chaining the adapters should be pretty good. For more even current though, a specific purpose pcb could be made like I did for the freeway mobos seen earlier in the thread.

In any case, if a fuse is wanted, buy a axial glass fuse and solder inline. 😀

I am going to, at 3.3v the rail on this PS can put out over 20 amps and I could see it being a problem in an accidental short.

Post pics of it installed when you get it all setup 😀

Thank you Sphere478 for your work! Just ordered some of these boards to be soldered to a 430TX board I have to mount a TNT2 that requires indeed 3.3V and I don't want to mess with wires on the back and do a botch job 😜

I'll let you know when installed and send some photos!

Excellent!!! Look forward to results!

mmx_91 wrote on 2022-10-31, 14:51:

Thank you Sphere478 for your work! Just ordered some of these boards to be soldered to a 430TX board I have to mount a TNT2 that requires indeed 3.3V and I don't want to mess with wires on the back and do a botch job 😜

I'll let you know when installed and send some photos!

My AN430TX already has 3.3V. Yours does not?

I validate this with one of those cheap Rage LX PCI cards, which absolutely need 3.3V.

Kahenraz wrote on 2022-10-31, 19:06:

My AN430TX already has 3.3V. Yours does not?

I validate this with one of those cheap Rage LX PCI cards, which absolutely need 3.3V.

As far as I've been investigated, it depends on the board. An ATX board will have 3.3v pci almost for sure, but for AT boards it just depends.

The AT power supply standard did not offer a 3.3v rail, and those boards had different levels of integration for this voltage. Most only offered a small converter for CPU, memory buses and so on, but not for PCI.

Other board I have in hand, a later Aladdin V based one with AGP, feeds 3.3voltage to PCI when using an ATX power supply but none if you use an AT one. Very strange.

We do this only for the sake of science! I'm curious about this topic. This 430TX board I'm refering to is kind of a Frankestein xD. It's a basic PCPartner board I have for testing purposes, which have survived to a broken socket, failed bios updates, burned USB traces... Let's add 3.3v for PCI 😀

That sounds like a perfect candidate. Please share photos of it decides to burst into flames out of spite.

You guys crack me up. Happy frankensteining!! Yes do keep us updated!!