exxos's Atari, Amiga & retro forum

A few months ago, I came into possession of this curious looking hand-soldered and very bodged board, bearing only the text "ATARI MIDI", despite having no apparent connection to MIDI...


It was attached via a ribbon cable to this LCD screen of about 9.5" diagonal...


At first I thought, "could this be an STPad prototype?" But no, inspection of the board revealed that the processor is an OKI 80C88 and right next to it is a DIP M74029, the same CPU and ASIC combination used in the Portfolio, which was designed by DIP Research Ltd. in the UK. The two ROMs, labelled "BD 1.68" and "15 AUG 90", suggested that whatever this is, it's a little bit newer than the Portfolio, which was released in 1989.

First thing, I dumped the precious contents of the ROMs (attached to this post should anyone wish to inspect), which were thankfully still readable after more than 30 years, and sure enough, they do contain a version of DIP-DOS, the operating system used on the Portfolio. I knew that DIP-DOS in the Portfolio had an easter egg listing some of the DIP crew responsible for the project, so I searched for that in the ROM dump, and found it, with a very slightly different list:


So, this was definitely a Portfolio relative of some kind. I decided it was time to try to get some expert opinion on the subject, and I got in email contact with John Brett and David Frodsham, both of whom were interested in what I'd found, and it was David who confirmed that this is indeed a prototype for the large screen Portfolio 2, which never made it to market. David said, "I think what you have there is something extremely rare: a prototype of a large screen Atari Portfolio. It never made it to market but we were contracted to build a prototype."

This was a bit of a bombshell, as I'd never heard of any large screen Portfolio in development. I have since discovered a couple of references in old publications from around the time which rumoured the existence of a followup product never marketed, but that's it. It seems to have disappeared into history at that point.

Coming up very soon in a second post, does it work?

Great stuff, nice find!

So, having dumped the ROMs, it was time to determine if this thing could still run. The board looked visually in excellent condition. There's a lot of flux on it, because it's all hand soldered, and I found a couple of roving solder balls, but under the microscope, it all looked pretty good.

Power input to the board is provided via a barrel jack as well as two test terminals helpfully labelled + and -. I pulled out the schematics for the released Portfolio 1 and built up schematics for the DC-DC section of this prototype board in KiCad, and unsurprisingly, it's virtually identical to the same section of the Portfolio 1. The board passed all my electrical checks, everything is connected as it should be, no shorts, etc., so it was time to power it up!

I set my bench PSU to 4.5 VDC (same power section as Portfolio 1, so this thing is designed to be powered by 3xAA cells), with a 150 mA current limit, and powered it up. Nothing on screen, and the PSU dropped down to around 2 VDC, which means the current limiter was hit. So I raised the current limiter to 300 mA and tried again, and...


:yay: It boots! The LCD is obviously not fully functional, but the BIOS is clearly there and starting up, presenting the DIP POST splash. After about 10 seconds it moves on to a keyboard selection menu:


And after sitting there for about 30 seconds it times out, and presents the standard DOS date prompt:


As I am presently unable to give it any input, this is as far as things get for now. I have verified that the keyboard connector is the same type as the Portfolio keyboard connector, and connecting to the same pins on the DIP chip, so I am assuming that a Portfolio keyboard will work, but I have not yet tested this.

The screen is somewhat more damaged than these photos show. It's missing half of the driver chips along the short dimension, and one of the two present is malfunctioning, so only the top quarter of the screen works, and even that is missing vertical sections. The screen is a Sharp part, but no reference to that particular part number appears online anywhere. However, as it's driven by an off-the-shelf Chips & Technologies 82C425 CGA LCD/CRT controller, a replacement should be relatively easy to source, and I have ordered a part that I believe will be compatible.

I don't want to connect the keyboard and take this any further until after I've gotten the replacement screen attached, because when I do get to the point of interacting with the device, I want the "full experience"!

Full size copies of all the images in these posts are available here.

More to come. Comments, thoughts, and suggestions from others welcome!

Interesting finding, it could be a prototype of Portfolio's successor Sharp PC 3000 (made also by DIP) https://en.m.wikipedia.org/wiki/Sharp_PC-3000

Over in the other forum, there is someone who was part of the Portfolio development team at DIP and wrote a book about it: https://www.atari-forum.com/viewtopic.p ... 86#p422786. Probably, he could provide further insight.

Cyprian wrote: 19 Jun 2022 11:46 Interesting finding, it could be a prototype of Portfolio's successor Sharp PC 3000 (made also by DIP)

I agree that this is somewhere in between the Portfolio and the PC-3000. Probably closer to the Portfolio, and David confirms that DIP were contracted to build a prototype.

I noticed when poking through the ROM that there is a reference to pressing the Atari key on the keyboard for a help screen. Of course this key did not exist on the PC-3000.

And of course there's the fact that it says "ATARI" right on the board. ;)

wow very nice find ! :)

Really neat find, very interesting.

That’s too cool, truly fascinating! Thanks for sharing. Neat that it still kind of works!

So, the source for a Sharp screen that is very similar to the one originally connected to the prototype fell through, but I found a Seiko 640x200 LCD that is compatible. However, it requires a -24 VDC drive voltage and an additional negative voltage to control contrast (sweet spot here ended up being -16). As the Portfolio board is generating only -17 VDC, I decided it was finally time to upgrade my old single channel bench PSU to something better, and I got a OWON ODP3033 3-channel PSU, and so far I'm very happy with it.

On to the good stuff!

I hooked up the new screen, the PSU, and a Portfolio keyboard, and ended up with a setup that looks like this:


The BIOS POST screen is now complete:


Here's how things look right after dropping into DIP-DOS:


Built-in Lotus 123-compatible spreadsheet:


Diary, which can show alongside DIP-DOS (but does not appear to multitask):


Calculator:


Text editor, with requisite greets:


Settings menu, where various things can be done, including inverting and adjusting the display:


Also the size and position of the various apps can be controlled from here:


Next, I stuck in the one Portfolio (actually DIP Pocket PC) card I have, to verify that this board can run Portfolio software off Portfolio cards:


...which it can!

And finally, pulling up the old Portfolio easter egg, which is still accessed in the same way, although with a slightly different output:


So, everything does indeed appear to be working just fine, some 32 years later. I think I will try to get all of this set up in some manner appropriate for display (and not requiring a bench PSU to make it work!), but that'll likely wait until I have fewer things on my plate, so unless someone wants to know or see something in particular, I think this project is done for now!