Sneak Peek: Rejuvenator Board Schematic Nears Completion

[intric8]

Back in August, 2018, I shipped my unpopulated Rejuvenator board - the only known example in existence - to AmigaLove member joethezombie (Joe). The plan was for Joe to take the board and create brand new schematics from it. As has been previously established, all previous artwork is believed to have been lost. To recreate the Rejuvenator, we have to start from scratch.

Joe has put an incredible amount of work into this project. As such, he would like to share with the community his progress up to this point. The schematics themselves are not complete and not ready for prime-time. But they are very close barring a few unanswered questions I hope we can resolve this week or soon thereafter.

Behold!

3D rendering of a future fully-populated Rejuvenator board (minus the Agnus socket).

From Joe on the making of new schematics:

The KiCAD software creates the 3D model from the board layout automatically, so the 3D render is a nice feature that doesn’t require any additional work other than downloading the models for each part.

Joe continued:

The "x-ray" is the actual board design I put together in KiCAD. Each color represents a layer on the 4 layer board. I forgot to un-hide one of the layers before taking the screenshot— it’s missing the yellow, layer 2, so there’s actually many additional traces you can’t see there.

X-ray view of the Rejuvenator schematics as seen today, WIP.

This is simply a herculean effort and a non-trivial amount of work and love has gone into this project thus far. I've been trying hard to keep my personal emotions out of this. But you guys, this is starting to feel real. My level of excitement is definitely starting to turn up a few notches.

In addition to Joe's brilliant efforts, SEA-CCC.org member Christian has built some adapters for the RAM. This will allow the use of much more common and accessible RAM chips as well as bump those with the correct Agnus up to 2MB. We will be testing these adapters tomorrow (October 3, 2018) and discuss next steps for reading the logic on the PAL chips.

RAM adapters soon to be tested in our working Rejuvenator board.

Progress! Good times my friends.

[Mr.Toast]

Very cool. I wonder if my A1000 still works? And, how hard it might be to source a 1MB+ agnus chip these days?

[nonarkitten]

Which Agnus do we need?

[intric8]

@nonarkitten the stock configuration is the 1MB ECS Fat Agnus, i.e. 8372A.

Assuming we get the RAM situation sorted out, one could install the rather rare and harder to find 8372AB.

In the future, we hope to eventually modify the rejuvenator to accommodate somewhat more common versions like from the 600, but that's a ways off.

First: we need to simply prove we can reverse engineer the original at all. Then we can iterate after that.

[A10001986]

The 8372A is easily available, eg on ebay. When looking for a replacement for the 8372B (or AB; they are identical) Just beware of the 8375 of which there is a gazillion of versions, NOT pin compatible to each other.

The closest match for the 8372B/AB, ie for 2MB, is the 318069-18 (PAL; the NTSC equivalent is -19). Works both in an A3000 and my Phoenix board. (Minor mod needed. A3000: R203 removed, J200 bridged with a 100nF cap; this simply due to the fact that the 8375 is not jumper-switchable between PAL and NTSC. The resistor to be removed is a pull-up or down and the jumper to bridge is actually the PAL/NTSC jumper that needs to be changed to deliver Vbb which is done through that capacitor. PAL and NTSC in this context only means the default boot mode; all 8375s are software switchable just like the 8372.)

A list of versions is here.
Unfortunately it is in German, but the amount of text is manageable.

[nonarkitten]

So we want the 8327[A]B, 318069-03, or the 8375 318069-18 (PAL) or 318069-19 (NTSC), the latter needing the Vbb "fix" for stable operation. Presently, the only NOS available are the 8375 318069-10 which are only compatible with the 500+/600 models. The other three are made from unobtanium.

[intric8]

That is 100% correct on all fronts. I happen to have lucked into one of the rare Agnus chips (seen on the far-left).

One of the rarest elements in the Periodic Chart of Agnuses.

The vast majority of people will be slapping in the 1MB chip Agnus with this until future revs of the board can be modified to support different options - the NOS A600 version being the most logical next step.

[nonarkitten]

I have to say, 1MB of Chip RAM in an Amiga 1000 will still be a welcome addition. But here's an odd thought. Would the MegaChip-like expanders work? These are (now) mostly based on the NOS Agnus but must rewire the pins to work in an Amiga 500. This would, in theory, give us 2MB without having to further mod the Rejuvenator (which we might want to do ANYWAY, since the MegaChips sell for a ton on eBay right now). Even Jens was selling some MegaChip clones which sold out quick, but maybe he'll make some more? Also on the subject of stacking a mod on a mod, I'm guessing the Indivision ECS would work well on here too?

[intric8]

Would the MegaChip-like expanders work?

I honestly don't know. I've had that same exact thought go through my head as well. I asked my friend in the Seattle Commodore Computer Club and he said "You could use the megaChip that Jens [from Individual Computers] is talking about making. But if we can successfully change the pinout, then everyone could use the A600 Agnus." So that sounds like a no to me (if you mean the old school ones).

I'm guessing the Indivision ECS would work well on here too?

Maybe? By default, no. But if you used a Paula relocation board, it probably would fit at that point. Hope this helps!

And holy smoke! Wait till I get a chance to post the pics from our tests tonight. You guys are ALL going to really like what you see.

[A10001986]

If the MegiChip is intended to be put in a socket originally occupied by a 8372A, I would say it should work on this board, too.

Jens (icomp) has new ones (well, it's his own design) for sale right now. (This is no endorsement)