1088XEL Alternative Mother-Board Project

[+mytek]

I don't like tons of boxes and cables lying around my desk, so for me yet abother psu wgere there is one slready in the Case is to write at least awkward. I could use that additional spersge to run internal floppy Drive Or whatever. These xases do contain 5.25 Drive bay, dont they?

 

Candle keep in mind that this board isn't solely destined for a PC case. My original project concept was to do a custom enclosure, but then due to the good suggestion by someone on this topic I decided to make it Mini-ITX form factor which still fits my original plans (and I always intended to use a cell phone charger for my PSU with a simple USB to Coaxial power adapter). However if this board gets put into a PC type case, and especially if someone wants to put their old style floppy and hard disk drives inside as well, then yes I will be allowing for that in my design, as well as providing the means to utilize a PC PSU.

 

As for the question pertaining to a 5.25" drive bay. Some do have it and some don't, it just depends upon what you would like to do. And some of the Mini-ITX enclosures are very tiny, only allowing for an internal hard drive, and not much more.

 

- Michael

[+mytek]

This enclosure is more likely to be something I would go for in order to keep my 1088XEL as compact as possible...

M350 Universal Mini-ITX enclosure by Mini-Box Black
by Mini-Box

 

I'm thinking that the recessed front rectangular area might make a good place for an SIO2SD LCD display to go (BTW, I have an internal SIO connection header already planned for adding something like this). My version would not use a cart, a floppy, or an actual hard drive, and instead would opt for using the SIO2SD as my internal drive and the SIO2PC-USB for a PC based drive and printer.

 

 

Power would be supplied by a phone charger (example only)...

USB Charger, UBP Quick Charge 2A 10W Universal Travel Wall Power Adapter for Smartphones and Tablets
by UBP

 

And connected via a USB to coaxial power adapter cord...

 

 

90° Right Angle USB 2.0 Male to 5V DC Power 5.5mm Barrel Connector Cable Cord

 

 

- Michael

[Kyle22]

Since you have a U1M in there, why not put SIDE2 circuitry in there? It just makes sense.

[+mytek]

Since you have a U1M in there, why not put SIDE2 circuitry in there? It just makes sense.

 

Yes I could do that as well Many possibilities for sure. Although the on-board battery-backed RTC and SDX are kind of redundant and not needed due to the U1MB taking over those functions. Really all I need is the CF (or SD) card functionality.

 

- Michael

[+mytek]

I just ordered one of these...

Figured it was time to verify my layout against something real

 

- Michael

[Dropcheck]

I just ordered one of these...

Figured it was time to verify my layout against something real

 

- Michael

 

What's the height of the enclosure? Looks to be only a couple three inches. Might not be enough height for the PBI cards. Wouldn't you need around 4-5 inches realistically?

[+mytek]

 

What's the height of the enclosure? Looks to be only a couple three inches. Might not be enough height for the PBI cards. Wouldn't you need around 4-5 inches realistically?

 

Good question

 

- M350 Enclosure Size: 192 (7.60") x 210 (8.26") x 62 (2.44")

 

Realistically there isn't a PBI card in existence that would directly plug-in using the interface method I've chosen (this is not a standard XL PBI card edge interface). However there are some existing PBI devices that utilize a ribbon cable connector which would likely be compatible, and since the ribbon allows some flexibility, could be made to fit either internally or externally depending upon the application. And there is room for a ribbon to exit out the back above the built-in port connectors. But this is all mute for what I am personally looking for in my application, since I have no immediate plans to use any standard XL PBI device. But lets say we did want a PBI card to directly plug in like an edge card device (after all I have provided for that possibility). A custom PBI card (whatever that may be) could be designed to fit in even the limited overhead of this enclosure I plan to use. And if that really isn't suitable, then just target another enclosure with more room since there are quite a few choices out there to choose from. Bottom line is that the 1088XEL is not destined for any particular Mini-ITX enclosure, but it will be designed to fit inside any Mini-ITX enclosure the end user so desires. So the only things from a layout standpoint I need to be concerned with are the following...

• Board Footprint: 17 x 17 CM
• Mounting holes: 4 that match Mini-ITX form factor
• Port Connections: Must be located in the back, and not to extend beyond the Mini-ITX designated area provided for these ports
• Plug-in Card: Normally at least one (and sometimes two) PCI card(s) can be supported with only one having direct access to the back (since there are no PCI cards for an A8, I've allocated this functionality to PBI)
• Overhead of 1088XEL with highest profile upgrade, not to exceed available space of smallest target Mini-ITX enclosure

So this particular Mini-ITX enclosure will make a good reference to use for verification of all the listed concerns.

 

For me the whole reason behind this project was to make a compact Atari designed to be more akin to the MAC mini packaging. And at 1/2 the size of an XEGS, this will suit my purposes well.

 

BTW, this particular enclosure I've chosen does have some interesting accessory brackets available that might work well for mounting a ribbon connected PBI device...

And it can be mounted to the back of a LCD monitor making for a very nice all-in-one type system...

 

 

 

 

- Michael

Edited February 14, 2017 by mytekcontrols

[+orpheuswaking]

I'm loving the enclosure conversation, but I am still a sucker for a custom case with aluminum end plates. One that could sit right next to my sDrive NUXX.

[Dropcheck]

I'm not really thinking a standard PBI device either. I'm aware of the non-standard internal bus structure for the slots. By the time you subtract the height of the mainboard, the height taken for the connectors on both the mainboard and the PBI card, you are looking at barely 2 inches for the electronics on the card. Even with surface mounted electronics you're going to need more than a max height of 2 inches on a PBI card. If you use th technology you are definitely going to need more.

 

If you try to rationalize using a ribbon cable to connect with an external PBI enclosure, why do you have internal slots? It's a waste of space and purpose and now you have spaghetti cabling and cobbled together PBI enclosures. Stick a horizontal PBI connector on the rear of the mainboard and be done. But then you violate the standards of the Mini-ITX format and you lose the ability to use ready made cases.

 

Looking at the animation, it looks like the case is assuming a horizontal backplane riser to actually house two internal cards. The card cutouts are horizontal, not vertical. Could you redesign the layout to take advantage of that?

[+mytek]

If you try to rationalize using a ribbon cable to connect with an external PBI enclosure, why do you have internal slots? It's a waste of space and purpose and now you have spaghetti cabling and cobbled together PBI enclosures. Stick a horizontal PBI connector on the rear of the mainboard and be done. But then you violate the standards of the Mini-ITX format and you lose the ability to use ready made cases.

 

I was just thinking out loud when I made that suggestion, not having reached the end point of that thinking process. What I really have in mind and based on if there is enough room to do so, would be to mount another connector to a custom bezel at the rear, which would be connected via a 'ribbon cable' to one of the on-board PBI connectors. This would then provide an easily accessible external PBI port, and not take up the area needed by the other motherboard mounted ports. First things first, I need to get my hands on the proposed enclosure and scope out the situation. However I believe I can use something like Front Panel Designer to create the bezel (I've made things with their process before --- see here). As to the question of why have internal slots, it makes perfect sense to me for an IDE interface to a floppy and/or hard drive. this is how a PC would do it as well. What's not to understand?

 

By the time you subtract the height of the mainboard, the height taken for the connectors on both the mainboard and the PBI card, you are looking at barely 2 inches for the electronics on the card. Even with surface mounted electronics you're going to need more than a max height of 2 inches on a PBI card. If you use th technology you are definitely going to need more.

Of course this is merely speculation likely based on a particular PBI device you had in mind. Because I'm fairly sure that a PCB with an area based on approximately 2" x 4" dimensions (which should fit either slot) would actually hold a lot of SMD technology. But it really comes down to what will that device need to do? And to be perfectly clear I have no plans at this time to design any PBI devices, the port(s) are simply there in case I do at some later time. And there is a very good chance that I will simply use one of the available slots with a break-out board to allow for scoping and experimentation. Nothing is set in stone when it comes to why they are there or how they are to be used. And I know you didn't mean anything bad by saying it was a waste of space, but it is my space to waste however I choose to .

 

But once again let me also stress that the enclosure 'I am' choosing to use, is not by a long shot the only type available. If you have been following this topic, which I know you have been, then you should also be aware that there are enclosures that will yield much more room above the motherboard than the one 'I' want to use for my 'personal' project . So only I have limited myself in that choice, but that doesn't mean that someone else has to.

 

- Michael

[BillC]

The simplest way to implement an external PBI via ribbon cable would be to use a 50 conductor Centronics IDC connector, these were used for early external SCSI devices and are designed to be easily plugged/unplugged. I believe FJC used one when adding a PBI to a 1200XL.

 

http://www.showmecables.com/product/50-Pin-Female-Centronics-Connector-Ribbon-Cable.aspx

 

 

[Matej]

I will put it into my not working Atari ST - Atari STF case!!! Only problem will be keyboard... Hmm arduino or teensy ST to PS/2 keyboard.

[+mytek]

The simplest way to implement an external PBI via ribbon cable would be to use a 50 conductor Centronics IDC connector, these were used for early external SCSI devices and are designed to be easily plugged/unplugged. I believe FJC used one when adding a PBI to a 1200XL.

 

http://www.showmecables.com/product/50-Pin-Female-Centronics-Connector-Ribbon-Cable.aspx

 

I do like that connector, but due to its thickness there might not be enough room. If you look at the post just before this one you'll see that the bezels aren't very tall.

 

- Michael

[+mytek]

I will put it into my not working Atari ST - Atari STF case!!! Only problem will be keyboard... Hmm arduino or teensy ST to PS/2 keyboard.

Lots of space leftover inside that ST case. Looks like two 1088XEL boards would fit side by side. Hmm... makes for an interesting possibility.

 

- Michael

[AtariNerd]

^Yup, lots of space for add-ons - or even to have a modern PC, sitting along-side the Atari.

[+mytek]

I'm contemplating a change from the XL PBI to the 130XE method (with only one slot position). Nothing firm yet, just speculating. Anyway if someone has the exact spacing distance between the Cart and ECU connectors (referencing Pin 1 on both) that would be most helpful for me to test out some ideas.

 

Thanks,

 

- Michael

Edited February 15, 2017 by mytekcontrols

[candle]

it's on 100mil raster, so just count pins as it was single connector (fill up the gap)

[+Stephen]

I'm contemplating a change from the XL PBI to the 130XE method (with only one slot position). Nothing firm yet, just speculating. Anyway if someone has the exact spacing distance between the Cart and ECU connectors (referencing Pin 1 on both) that would be most helpful for me to test out some ideas.

 

Thanks,

 

- Michael

I measured from center pin to center pin, and got 60.99mm, so we'll call it 61mm.

[ivop]

That's probably 2400mil (60.96mm)

[BillC]

I just checked an ECI to PBI adapter against a old 586 motherboard, it is the correct width to plug into an 8-bit ISA slot(62 conductor)

[+mytek]

Thank you guys for the dimensional info. I see I made a boo boo on the name (i.e., used ECU instead of correct ECI). ivop is 60.96 mm accurate or just an educated guess?

 

- Michael

[ivop]

ivop is 60.96 mm accurate or just an educated guess?

 

Stephen measured 60.99mm, so I just ran

$ units -1 "60.99mm" mil
    * 2401.1811

I figured that was close enough to 2400 on 100 mil grid. So instead of rounding up to 61mm, it was actually 0.03mm shorter

 

I just held a perfboard along the ECI connector of the 130XE that I'm currently fixing and all the pins line up perfectly. The whole connector pair is 3000 mil.

Edited February 15, 2017 by ivop

[+mytek]

 

Stephen measured 60.99mm, so I just ran

$ units -1 "60.99mm" mil
    * 2401.1811

I figured that was close enough to 2400 on 100 mil grid. So instead of rounding up to 61mm, it was actually 0.03mm shorter

 

I just held a perfboard along the ECI connector of the 130XE that I'm currently fixing and all the pins line up perfectly. The whole connector pair is 3000 mil.

 

Sounds good

 

Thanks

 

- Michael

[+mytek]

I found a much better document that gives better specifics on the Mini-ITX PCI slot location, as well as the card and bracket dimensional aspects: MINI_ITX_VIEWS.pdf

 

In the white paper I was using as a reference, it failed to really show specifically where on the connector the reference point was for the distance from the edge of the motherboard. But as we can see here, it relates to one of the inside edges of the card edge connector. This is important even in our non-PCI usage, since it is still important that a parallel bus card line up with the metal bracket in some fashion on the rear of the enclosure. However please keep in mind that unless you luck out and find a bracket with the specific connector cut-outs required for a given parallel device board, we are still looking at a custom bracket having connector holes in the correct location.

 

 

Note: not all Mini-ITX enclosures have a PCI card rear bracket cut-out.

 

 

If you take a peek at the PDF I attached, you'll see that all views including an isometric have been included. What isn't shown is the distance from the back edge where the connector sits, although for our purposes that really is a mute point since we aren't talking about plugging in a PCI card anyway. Since I have chosen to go with the 130XE CART/ECI configuration instead of an XL PBI, I will likely position the CART centered between the front and back edge of the board. This will establish a standard location for the 1088XEL parallel bus slot, and can be factored in for any future expansion cards that may or may not appear. That dimension will only be critical for a board that requires rear access.

 

- Michael

 

 

[npturton]

So you need the U1MB for any OS?