A4000 DIY Motherboard

[indigolemon]

Originally Posted by MigaTech

@elenachen, how big is this new board of yours going to be? I ask this as an idea of converting existing PC cases to suit your design.

From post 1 of this very thread:

Originally Posted by elenachen

I'm thinking of doing my own A4000 Motherboard in an ATX format.

So standard ATX size, thereby removing the need for any converting of cases?

[elenachen]

Originally Posted by MigaTech

@elenachen, how big is this new board of yours going to be? I ask this as an idea of converting existing PC cases to suit your design.

I plan to implement the Zorro Slots, so it'll have to be E-ATX. Otherwise the width wouldn't suffice.

[Magic]

It looks like your off to a great start. Nice shop too

[Mathesar]

And in KiCad! I am happy already :-)

[elenachen]

Things I need to know are in Post 1 on first Page ;-)

[MigaTech]

Originally Posted by elenachen

I plan to implement the Zorro Slots, so it'll have to be E-ATX. Otherwise the width wouldn't suffice.

Yes I figured you would have to reintroduce the Zorro ports, do you plan on adding PCI? E ATX is OK to work with, albeit the PSU location still has to be changed.

Yes was aware that you had mentioned it in first post. I really wanted actual sizes in CM's.

[elenachen]

E-ATX-Format: 305 mm × 330 mm (12″ × 13″) --> but watch out, the actual Zorro Cards are about a cm longer than the width of the Board. So the Case should have a little more width in the Board Area, so about 34cm? Sry never had a Zorro Card in my hands. Working with just the specifications of it

PCI won't be there in first release. PSU location depends on Case you'are using. Most older Models have them on the Top, but the trend is going to the bottom of the cases. Will be a Standard ATX Connector anyways --> worst case you need a ATX Extender Cable ;-)

[kgc210]

Full Zorro cards are 337mm long (PCB)
The rear of the card (front of case) is about 44mm from the finger edge.

E-ATX Cases tend to support a graphics card 355 - 395mm long so most should be fine.
If you are going to have Zorro slots on the board and not a riser also consider the A4000T Schematics as well.

[elenachen]

Originally Posted by kgc210

Full Zorro cards are 337mm long (PCB)
The rear of the card (front of case) is about 44mm from the finger edge.

E-ATX Cases tend to support a graphics card 355 - 395mm long so most should be fine.
If you are going to have Zorro slots on the board and not a riser also consider the A4000T Schematics as well.

Yep, printed both schematics for good comparison to do this properly with the zorro bus.

Does anyone know about the Keylock mechanism? if the cable is unplugged, what happens? Is the Keyboard locked or usable? Want to leave a few components out if possible

[kgc210]

My A4000T board isn't working, but on my A4000 the Keyboard lock is never plugged in and the keyboard works.

Just had a look at pricing on a PCB that large, you are looking at £12 - £15 each depending on how many you buy. That's not including postage from China. Not bad price really!

[elenachen]

Thx for that info!

Didn't bother with the cost for the Board for now. Will be a 4 Layer job

[kgc210]

Yea that's what I priced for (4 layer), was expecting something really daft like £80 per board.

[elenachen]

Nope, making PCBs these days is actually ridiculously cheap. But i think the components on the board will quite add up.....

[MigaTech]

From the sizes I am unsure if the PSU can run parallel with the board? It may have to be mounted slightly above the M/B, over a non crucial area. Unless dimension are greater or lesser on both board and case?

Also PSU related, what power range was you considering safe, 350w upwards? Don't think stabilising is required but check anyways.

Are all input ports going to the rear? Daft question but have to ask, as on the A2K the mouse and K/B inputs, are to the front.

[kgc210]

You want to look for a PSU with min 20A on 5v. Seen some as low as 10A

[elenachen]

So, cleared out the Keyboard lock section. 8 Parts less to worry about

[elenachen]

Originally Posted by kgc210

You want to look for a PSU with min 20A on 5v. Seen some as low as 10A

And yes, on the A4000 the strain is on the 5V line. Those lines were quite high amperage before the Pentium 4 times in ATX Supplys. So if someone of you got a old supply lying about, check the 5V amperage. It could be much higher than on new supplys, since those rely heavily on the 12V rail.

[Locutus]

You could also consider not providing a ATX connector and instructing end users to use a proper powersupply.

The 5V rail off a ATX supply with barely any load on its main 12V rail is usually terrible.

[elenachen]

Originally Posted by Locutus

You could also consider not providing a ATX connector and instructing end users to use a proper powersupply.

The 5V rail off a ATX supply with barely any load on its main 12V rail is usually terrible.

Well, if they want, they can build their own adapters to the ATX Power slot.....or put a resistive load on the 12V Rail.

Don't want to do some mock up Adapter or a need for a proper Isolated Bench Power Supply......

I can give infos on a howto for loading the 12V Rail while releasing the board.

[MigaTech]

Most modern towers have large LED cooling fans, usually around X2 to 3. These should be enough to help put extra load on the PSU.

Using a latch switch rather than PTM would also help keep PWR/ON signal constant.