This is an amazing replica of the Commodore A2386SX PC bridgeboard, you can find out more about the project here. There is also a discussion forum about the card on the German A1K forum (just use auto translate in your browser if you dont speak German).

Background

The A2386SX was the best PC bridgeboard Commodore made for the Amiga, it was based on a 386 CPU, could be expanded to 8 MB and enabled you to transform an Amiga in a multi CPU system that could run tasks in parallell on both CPUs, one in Amiga Workbench and the other in MS-DOS on the bridgeboard – at the same time. You could for example hop in to MS-DOS and run your programs and then multitask back to Workbench while programs where running in both environments.

This is a beautiful built replica of the A2386SX PC bridgeboard by Commodore.

I got my PCB late in Q1 after contemplating if it was even possible for me to build this card at all. The main problem was finding all the parts and programming some of the chips. But I quickly came to realization that it was actually possible to locate almost all the parts if I pulled the trigger at the right moment.

My main goal of running the card is to have access to multi channel module players such as Cubic Player and to be able to play PC modules in MS-DOS with a Sound Blaster 16. I would also like to dive into some old MS-DOS applications I used to use 30 years ago and play some old DOS game or two. But the main attraction is PC music without having to get a separate PC for that.

Some notes on parts and building the A2386SX project

There are some very rare parts required for the A2386SX bridgeboard. The rarest chips are the two socketed PLCC84 Commodore chips and the PC chipset in the middle of the card.

The Commodore chips can be taken from 2088 and 2286 Bridgeboards (they are the same), they might pop up on eBay, but consider that a miracle if they show up. I got my chips from a cheap 2088 that I bought second hand last year. Did not know what to do with it at the time, but it was too cheap to pass up on and I am glad about that now.

The PC chipset should in theory be easy to find online, but so far, I have only been able to locate one of the chips. The other chip needs to be ordered in bulk from a specialist in rare chips and is costly (and will probably only go up in price). I thought it was possible to find an old motherboard and desolder them from there, if you find a motherboard that has them – consider that a miracle!

Then we have other obscure chips such as the floppy controller, programmable chips (that needs a special vintage programmer or someone with better skills than me in understanding how to program them with a modern device) – not really a problem to find.

Memory can be found from obscure part specialists (remember you need two types of memory). The CPU is available on eBay, but if you want the faster 486 that is compatible with the card, good luck, as said, miracles can happen!

Bracket was sourced from another enthusiast who ordered a batch. 646 was taken from my donor A3000.

Full socket build

I did a full socket build, thinking it would make it easy to error check or replace chips.

486 chip instead of 386 chip

So while this is a 386 bridgeboard it uses a 486. I did some research earlier this year when I built my card, unfortunately I have forgotten the exact details, but it is possible to use a special 486 CPU on the board as they are the same size. I think what is most important is that the voltage level is the same as the 386 that it is supposed to use and you need to fiidle with the BIOS.

This mod works on the original Commodore A2386SX card also. This is a nobrainer for me since I grew up on 486 PCs.

Failed test run and successful test run!

So after having received more than 10 packages from around the world and a the main passives from Mouser I decided to build it up.

I was super excited to do the first test run after receiving the programmed chips. Bummer – But the first test run failed – the card refused to run!

Most of my projects I build usually run fine, if there are any errors it is usually a bad solder joint on a surface mounted component. In this case I knew I would never figure it out myself, so I sent it off to a friend in the hobby to get it checked.

Turned out that I had used the wrong memory (I had used the memory from my donor Amiga 3000), there was also an error in the BOM that has since been updated where bussed resistor nets where specified instead of isolated (or was it vice versa).

Once I received the card I did another test run and could confirm the card to be fully running!

And then I realized, its going to take a shitload of time setting the card up.

Next steps

I probably did not realise how much work it would be to set this card up so thats why I will do it after summer. But the plan is to get MS-DOS 6.22 up and running with Windows 3.1. I will run an ISA graphics card and an ISA sound card and will also try to run the HDD off a partition on the Amiga HDD.

Would also love to build a second card, hopefully there will be an up to date model with chips replaced with CPLDs!

Here are five beautiful Multifix AGA purple PCBs. The Multifix AGA is a great Amiga scandoubler and flicker fixer. I will build two of these and sell the remaining cards once the built cards are tested, or do I build them all for myself (lol).

I plan to use them in the upcoming AmigaPCI (I will for sure build one once it is fully developed) and in my A4000T.

There are a couple of different hardware Kickstart solutions for the Amiga. The most proven one seems to be 27C400 chips that you can program in a T48 (with an adapter) and erase with UV light. If you buy a Kickstart from a retailer, that chip is probably an 27C400 EPROM. I dont like the UV light eraser, and the 27C400/27C800 chips are expensive, so I went looking for another solution that had the possibility to scale up in volume fine.

I don’t know what it is about burning Kickstarts for the Amiga but the topic is highly confusing at first. Not only do you have to have the correct byte swapped file (or build the ROM file correct if you want to run a custom ROM) but you need some kind of adapter to be able to program some of the solutions on modern cheap programmers.

This is not a tutorial in how to burn a Kickstart or how to build your own Kickstart, I suggest you schedule a weekend to do a deep dive into that topic. Then it sort of makes sense (I think).

No doubt in the future something like the KickSmash will probably be the defacto standard and I contemplated ordering a batch of PCBs and building a suite of KickSmashes for my fleet of Amigas. Instead I went with the FlashROM, because right here and now, it is possible to run FlashROM on all Amiga models while the KickSmash fits the Amiga 1200, Amiga 3000 and Amiga 4000 (and A4000T).

With new Kickstart ROMs being released fairly regularly these days. And the need to be able to build your own Kickstart so you can f.e. add ehide.device for a TF1260 system or PeterKs Icon library to the Kickstart, an easy way of updating Kickstart is IMHO, a must have, these days!

What is the FlashROM?

The FlashROM is basically a Kickstart replacement that you can program yourself – FlashROM has 1024 KB of space, meaning it can take two Kickstart files. This is great as it is possible to run one Kickstart ROM and one DiagROM rom on the same chip.

You change what bank you want to be active by setting a jumper on the pinouts between GND and A18.

If you do not need dual ROM functionality, just concatenate the same ROM twice and flash it to the EPROM.

Programming a Kickstart to the FlashROM

I use a T48 to program chips, an adapter was needed to be able to flash a Kickstart ROM to the FlashROM. I actually chickened out and just ordered a ready made programmer to reduce the complexity of this project, you can find out more information about the FlashROM adapter on Levo’s website.

Using the adapter is a breeze, just have to connect the wires correct and everything works just like programming any other chip. Erasing the EPROM is no different.

40 pin FlashROM

Here is the 40 pin FlashROM, this will go into my Amiga 500, Amiga 2000 and Amiga 4000 and so on.

42 pin FlashROM

Here is the 42 pin FlashROM, this will go into my Amiga Denise clone, Amiga 4000TX and Amiga 1200. One benefit of running it in a ReAmiga 1200 is that the jumper on the motherboard select which bank you want to be active.

Today I built a replica of the A3630 030 CPU card. The A3630 CPU card came with non CR Amiga 4000D models (the card works on the A4000T and on the A3000D/T also). The CPU card replica PCB is made by Chucky, read more about it here if you are interested in getting one yourself!

I got an (original Commodore made) A3630 in 2005, mainly for testing purposes. It was placed in storage for 15 years and I failed to check the capacitors on it. Sure enough the capacitors had leaked, the board had a fishy smell to it.

When I recapped the genuine C= A3630 board one solder pad lifted off the PCB (very common if capacitor have leaked for a long time). Sure, that is not a big issue, can be fixed quite easy with a bodge wire. But I thought rebuilding the A3630 it with a new ReA3630 PCB was a better option.

I decided to use the CPU and the KEL male edge connector from my current card instead of wasting a new mint in box unobtainium KEL connector from my stash on such a low end card. I removed the CPU from the card by using a hot air rework station. I used a desoldering gun to remove the KEL connector by desoldering each of the 200 solder points for it.

As you can see it is a quite simple card, especially if one do not mount the socket for the FPU. Since my main usage of this card is for testing purposes, the 33MHz FPU and crystal will be used on my ReA3000 instead.

The Multifix scandoubler is another great hardware project by talented Amiga hardware DIYselfer Matze. Read more about the Multifix AGA scandoubler and flicker fixer here.

What is a scandoubler and flicker fixer?

In my humble opinion a scandoubler is a must have for an Amiga. It lets you display native screen modes on a regular PC monitor. A flicker fixer is great to have also, it means you can use higher resolutions screenmodes without nasty flicker. There is however less reason to use flicker fixer modes in Workbench if you have an RTG graphics card since an RTG screen is faster than a flicker fixed screen typically.

Building and testing the Multifix AGA scandoubler and flicker fixer

I have to be honest, the first time I looked at the project page I did not have a clue on how to build it. But after having finished a couple of projects and being more used to projects with less documentation I felt ready to tackle this beautiful scandoubler.

The Multifix integrates well with the GBAP2++ Amiga RTG graphics card, being able to hook up directly to the graphics board. Doing so auto switches output between scandoubled/flickerfixed output and RTG output meaning, you could run the graphics board and scandoubler in one aligned Zorro slot and video slot.

It is difficult for me to say something about the video output since on a CRT the picture quality is probably superb. I do not have a CRT so can only test on modern flat screens. And also, I am using a cheap VGA to HDMI converter that introduces lots of banding on the output. The picture quality on my TFT is not as good as I get from an Indivision or ZZ9000. But even with the cheap VGA to HDMI converter, I have seen worse banding with other VGA scandoublers and with that said, the colors are correct. Overall I am very happy even if the picture quality is not as sharp as those other devices I mentioned. And the picture quality might be even better with another flat screen or a genuine VGA screen.

Difficult to find chips

There are some chips on the scandoubler that is a bit difficult to find and it is the OKI M5142 and NEC 42101. One card uses six chips of each. As usual, some chips pop up here and there on Ebay and there are the usual places where you can find these chips (Aliexpress). If you do some research you might even find clones of these chips that are fully compatible.

ADV7120KP30 is the same chip the A4000D uses, I got 5 from Aliexpress last year for my A4000D build so had 4 to chose from.

Anyways, building this Amiga scandoubler/flickerfixer is very straight foward.

Ports and switches on the back

The backside of the Multifix AGA is kind a busy, more so than a typical scandoubler that usually only has a 15 pin female VGA port.

You might wonder why it has two USB ports, two switches and an audio port on the back. I did too, and it is not quite obvious why by reading the documentation on Git-lab. Turns out, the USB ports provides power only, meaning, you can use these for devices that uses USB power such as VGA to HDMI converters. There is a pinout on the Multifix PCB so you can hook up the USB ports to your USB card saving one bracket space. The switches disables the flicker fixer functionality and the scandoubler functionality (useful if you just want to pass through video output). And what about the audio output? I think the card picks up audio from the video slot so you might be able to get sound from here (I am not sure though, will need to test that sometime).

Oh, and that bracket, it was not made by me, I found a guy on a1k.org who could sell me two (I plan to build another), I could never make one that good looking myself.