I think they used long lead ISA sockets and bent those 10 to fit in those holes. Look for ones designed for wire wrap, they have .5"+ long leads and you should be able to bend them 90' then about 1/8" in bend again 90' to work.... just my opinion.

What is your purpose in adding a second ISA slot?
If in order to use multiple ISA devices, why not try this.
Short on ISA slots? Try this.

Thanks for the link, but I’ve already read this (and related) threads. The purpose is to have two ISA soundcards in the system and not just for testing. So the ISA riser/backplane solution is not so convenient for me because it will require case modification and limit case selection. I’m considering it as a last resort option.

Horun wrote on 2024-01-10, 03:30:

I think they used long lead ISA sockets and bent those 10 to fit in those holes. Look for ones designed for wire wrap, they have .5"+ long leads and you should be able to bend them 90' then about 1/8" in bend again 90' to work.... just my opinion.

It’s an interesting idea! But where to source these wire wrap ISA connectors? I can’t just rip them off from some spare motherboard because the leads will be already shortened.

Never mind, I’ve found wire wrap ISA connectors on the Digikey. Unfortunately, judging by the connector blueprint, the connector has very limited space underneath it - if I want to make a 90 degree bend, the bend curvature radius should be minimal for the bent lead to fit under the connector (I.e. fit in the way that connector height won’t increase) and with such a small radius the lead could simply break.

Maybe someone from the community has two ISA slot P3B-F and could check if the second ISA connector really has bent pins underneath it?

I have a 2 Slot PB3-F. If i get chance i will try and get some pictures for you.

Bancho wrote on 2024-01-10, 08:33:

I have a 2 Slot PB3-F. If i get chance i will try and get some pictures for you.

Thanks! BTW, judging from the Wikipedia photo, the second ISA connector slightly differs from the first connector in design. I think it was made by different manufacturer. And it has some markings on the side, but it’s difficult to read them in this photo.

nevermind.

I got some pics the evening. Its too hard to capture how the legs are, but the bottom row of legs on the isa slot go inward at an angle. Board is a V1.04.

I tried my best to get a pic that shows how the pin sits in the slot.

Wow. So looks like they are really bent, though not at 90 degrees. And I think they are factory bent by the connector manufacturer - there was no point in using connector from different manufacturer if Asus could it themselves. Probably it’s a custom order but we’ll never know because EDA Inc. is long time defunct.

Well, I think the next step would be to buy a bunch of ISA connectors and try to bend the leads in the same way. And design a testbed PCB. And make a bending template.

Anyway, it should be a fun project. I’ll keep you posted but I’m a slowpoke (and have other work to do), so don’t expect any updates soon.

Bancho, thank you very much for the photos!

I got your PM, and I've only just had a chance to get to the motherboards.

I've taken a couple of photos of the two-slot P3B-F. Hopefully, these can help

janskjaer, thanks! Additional photos of this great board are always welcome 😀

I think it must be something like isa 98 pin with 90 degrees:

Or we can try to cut some plastic:

cryptowhale wrote on 2024-01-10, 07:27:

Never mind, I’ve found wire wrap ISA connectors on the Digikey.

Would you be able to share a link to that part or the digikey part number? I'm also interested in attempting this on my P3B-F.

Have you had much success on this since your last post?

nebular wrote on 2024-09-26, 18:06:

Would you be able to share a link to that part or the digikey part number?

EBC49DCMN-S420

nebular wrote on 2024-09-26, 18:06:

Have you had much success on this since your last post?

Nah, switched to other projects.

So I gave up and just bought 2-ISA P3B-F. Managed to get rev. 1.04. And I was lucky and got it for like $30 incl. shipping. Minor damage on IDE ports but overall pristine condition, though I don't know if it really works (don't have time to test right now).

Just documenting my latest findings on adding second ISA slot if someone will find a courage to actually do the thing.

The main reason I gave up was because of the difficulty of bending ISA slot pins in Harry Potter scar fashion. In my opinion it will be very hard to do it properly with just a pair of pliers and you'll need some DIY tooling to do it right.

I've searched the Internet for the source of the already-bent ISA slots and came to a conclusion that it was a custom order from ASUS (like their custom ASICs) and it's not possible to buy them separately. Though I managed to find two other ASUS mobos which theoretically can be used for cannibalization: MEW-L and P3W-E - these are again "variable ISA" variants which 2-ISA versions I actually saw on the Internet. And they are low-end Intel 810 boards with integrated GPU and no AGP - not such a big loss. The difficulty of desoldering such a big element (without damaging it!) from a multi-layer mobo which was designed to dissipate heat is a whole another topic.

Also, bear in mind, that desoldering 6th PCI slot and soldering 2nd ISA in it's place is not the end of the story - you should also get rid of the AS61256-8 IC with accompanying elements and solder two 0Ω resistors. AS61256-8 is a custom ASUS PCI arbiter that allows to extend the number of PCI slots - it is needed because 440BX own PCI arbiter supports maximum 5 PCI slots. Because you're lowering the number of PCI slots to 5, this additional PCI arbiter is not needed anymore. P3B-F schematics include relevant sheet that describes it (AS61256-8 is named HT82A001 on this sheet).

1 vs 2 ISA slots:

PCI arbiter schematics:

TL;DR:

I recommend just finding 2-ISA P3B-F. They are rare, yes, but this is possible. Though it took me like two years to find one for a decent price.

Another "low-effort" alternative is using ISA riser, as was already mentioned by zwrr:

zwrr wrote on 2024-01-10, 03:39:

What is your purpose in adding a second ISA slot?
If in order to use multiple ISA devices, why not try this.
Short on ISA slots? Try this.

What is the point? Well, there will be an empty port, unequalled, why desolder?

it will be very hard to do it properly with just a pair of pliers

I managed to bend it in 5 minutes. I bought it ISA on Aliexpress. I soldered second ISA on motherboard but not on p3b-f, on p3v4x (via), but not test. I'll check the work in a few days, there's no time yet.

Mr.Hunt, congratulations 😀

You have managed to do it with just a pair of pliers? Looks pretty neat! Though it's evident that there is some inconsistency in the bend shape - such things trigger my OCD and that's why I said that it will be hard to do it properly (well, at least in my case).

I'm glad that my posts acted as reverse psychology and encouraged someone to actually try the thing 😀

If it fits and solders down it's proper. You can't see the bends anymore after that 😀