Expanding an unexpandable ECI-less 65XE

[Peri Noid]

One of members of our Polish Atari forum, MatGuru, proposed a modification for an ECI-less 65XE (so probably all NTSC machines but also some of PAL ones, especially those sold here in Poland). This machine lacks an option of easy upgrade with external devices due to no ECI nor PBI expansion - it has only a cartridge slot. Of course, one may put a lot of stuff internally. I have such a machine with U1MB, VBXE, stereo and Rapidus but it's a different story. Still, I'm not able to connect to it some of my expansions like an IDE+2. So internal modifications are not always enough. And not always convinient. And here comes the MatGuru's idea. It's not very simple - the machine requires some modifications. Mainly, an original cartridge slot must be replaced with something with more connections - fortunately, a regular PCI-E x1 slot is of almost the same size and can be used to connect an external adapter with double ECI+Cartridge connectors. Yes, it means, that after this modification it's no longer possible to use an odl cartridge slot - but instead we're given 2 external ones. Which may be handy. All the modifications are explained in the attached PDF file (sorry if the translation is not perfect, blame me for this). The project was published so anyone can order the boards and try to install it. All the gerber files are also attached.

I installed this mod in one of my computers. The photos in the instalation manual and below depict this machine.

 

External view of an adapter:

 

Overview of internals (zip ties are used to fasten the chips only, it's my own idea; the GTIA chip has a fault, the board under it is a fixer and has nothing to do with the mod). The ECI signals must be connected to the motherboard - either directly or with an adapter (under ANTIC).

IDE+2 together with a 512KB external RAM expansion by @zaxon work well:

 

And so does the AVG cart with its ECI cable - additional 512KB of RAM available.

 

Of course, one may ask: but why? Because we can! 😉 

 

Additional files:

The instalation manual: ECIfix_EN.pdf

Gerber files and other stuff: ECIfix_resources.zip

 

I may add that with the components of this mod I managed to expand a 1200XL board with an ECI connector in a way, which (probably*) requires no case mods and a machine still can be used withot the ECI adapter in a regular way. But it's a different story.

(*probably - I have no original 1200XL case, I'm using a carton box instead )

[reifsnyderb]

Looks nice.  I'd recommend putting the /EXTENB signal on pin A of the ECI as well.  Then, you'd have all of the useful PBI signals.

 

Edit:  Changed to /EXTENB

Edited February 7 by reifsnyderb

[Peri Noid]

1 minute ago, reifsnyderb said:

Looks nice.  I'd recommend putting the /EXTSEL signal on pin A of the ECI as well.  Then, you'd have all of the useful PBI signals.

It is already there :-) All the ECI signals are present. Additionaly, the Phi2 signal is buffered to improve it's quality (a common source of problems).

Edited February 7 by Peri Noid

[reifsnyderb]

9 minutes ago, Peri Noid said:

It is already there 🙂

Maybe I missed something but I am not seeing /EXTENB in the schematics....

 

/EXTENB is nice to have to use PBI memory and simplifies the circuitry.

Edited February 7 by reifsnyderb

[Peri Noid]

/EXTSEL is there, taken from the Freddy chip leg (after cutting a trace from it to VCC). A proper pull-up resistor is also present.

There is no /EXTENB signal on an ECI port, it's on a PBI connector.

Edited February 7 by Peri Noid

[+Allan]

Although not a simple plug and play, this is a great idea since there are a bunch of NTSC 65XEs without a PBI. Now they are more useful/expandable.

 

Thanks for doing this.

[woj]

Why are there zipties on those chips there? So worn out they fall out?

[reifsnyderb]

9 minutes ago, Peri Noid said:

/EXTSEL is there, taken from the Freddy chip leg (after cutting a trace from it to VCC). A proper pull-up resistor is also present.

There is no /EXTENB signal on an ECI port, it's on a PBI connector.

Yes.  But the ECI has pin A reserved.  Putting /EXTENB on pin A would be an upgrade.

 

While it's been done, obviously, it's easier to make memory expansions with /EXTENB available.

 

 

 

 

[Peri Noid]

I understand. The question is - do such expansions exist? It should be possible to add this signal - yet, it would require additional motherboard modification (an additional AND gate combining /EXTSEL and /EXTENB) since the XE line does not handle it at all.

Edited February 7 by Peri Noid

[_The Doctor__]

Zip ties on chips is a good move especially when in adapters or carrier board, I highly recommend it. @woj

When chips and adapters are stacked then tend to work themselves out and more so when transported/shipped somewhere. This is a matter of physics, the further from the pcb the easier to topple the tree.

[reifsnyderb]

11 minutes ago, Peri Noid said:

I understand. The question is - do such expansions exist? It should be possible to add this signal - yet, it would require additional motherboard modification (an additional AND gate combining /EXTSEL and /EXTENB) since the XE line does not handle it at all.

With the 1090XL, /EXTENB is used for memory expansions.  To use the 1090XL (modernized version) and a memory card, with a 130XE, you either need to add an additional board that re-creates the /EXTENB signal or install a jumper in the 130XE.  (This uses a card slot and is an additional cost.) 

 

The jumper is described in the section of my parallel port document whereby pin A, of the ECI, is discussed:

 

"Probably the best use for this pin would be to connect it to pin 16 of the MMU (U3 / CO61608) so as to provide the missing EXTENB signal required by some memory upgrades. Note that making this connection would eliminate the requirement for a 1090 XE Compatibility Board, for memory cards, starting with the 2022 Reproduction of the 1090 XL Expansion System, R8."

 

 

 

 

 

Edited February 7 by reifsnyderb

[+Larry]

That looks really nice.  Very clean and neat-looking! 

 

BTW, there were a few NTSC 65XE's sold in the U.S. that had the ECI.  But from what I can tell, a very small percent.  I've got one, and it has the two-ram chip board, which I upgraded to 128K and then ultimately to 320K using a small board sold by A8-Maestro (More Than Games). 

[Peri Noid]

And it was very common here in Europe. Later they renamed them to 800XE (the same 130XE board with four 4-bit chips, just two of them populated).

[Peri Noid]

On 2/7/2024 at 10:30 PM, reifsnyderb said:

With the 1090XL, /EXTENB is used for memory expansions.  To use the 1090XL (modernized version) and a memory card, with a 130XE, you either need to add an additional board that re-creates the /EXTENB signal or install a jumper in the 130XE. 

I checked and it looks that there is no problem in connecting this signal. There is no dedicated pad on the B board here but pin A of the ECI connector on the expander is connected with a trace and is available at the B board. One just needs to solder to a tiny pad or to an edge socket pin. But it's a really marginal problem. So - it would be possible to connect a 1090XL to 65XE. 

Edited February 8 by Peri Noid