Modern hardware: GB A1000 replacement motherboard

The Amiga 1000 holds a special place in my affections for reasons explored before; it is what kicked the computer industry to deliver more innovation more often.

It was, understandably, replaced by Commodore with more powerful or more accessible machines throughout the life of the range but enthusiasts have continued to give it new leases of life far beyond what was ever expected of it. Whether you added more RAM using something like the Spirit Insider1000 plugged into the 68000 socket, or external boxes to replace the processor such as the Computer Systems Associates Turbo Amiga Tower 020 solution, or brought it up to the level of the 500 and 2000 using a Rejuvenator, there was and is an appeal about pimping the first Amiga to new levels. Perhaps the fact that nothing that followed in the Amiga range gave the revolution that the 1000 did is why this holds such a special place in people’s nostalgia.

The Phoenix Board was a replacement motherboard for your 1000 that gave features of a 2000 in the 1000 case such as display expansion connector, 2000 cpu connector, and multiple options for expansion. It was expensive, and rare.

In the 21st century, some enthusiasts decided to make a home based production run of the Phoenix. This went well.

And then Georg Braun started hacking, creating – amongst other things – a turbo card for the Phoenix which was produced in limited numbers.

The inimitable Herr Braun must have wanted more, and went the whole hog by designing his own Phoenix – the GB A1000.
The features are enough to make this the ultimate non-AGA Amiga: a 68030 and 68882 running at 50MHz, 8MB 32-bit fast SRAM, 2MB chip RAM, built in flicker fixer and scandoubler, built in autobooting IDE controller, 2 kickstart sockets, internal Zorro 2 slot, front expansion slot and side expansion slot, flash ROM for firmware… All in the original A1000 case, with no modifications whatsoever.

A group buy of blank boards was organised, and I was part of the run in 2008. The board is a work of art, truly, and is beautifully laid out and finished. A not insignificant challenge is that the board requires a lot of delicate soldering of surface mount devices, including very fine pitch devices such as the flash rom and SRAM – which incidentally isn’t cheap! After a lot of looking, researching, finding the necessary SMT bits and chips from Amigas, I came to the conclusion that I simply would not have time to complete the project and so sold the board.

Then, in December 2010, a completed board became available happily coinciding with my birthday. I might have jumped at the chance, but only a little, and the board arrived.

Challenge 0: It was missing a logic gate, the flicker fixer specialised memory modules, and had had a capacitor knocked off in transit. Thankfully a quick farnells order, a scavenge around a faulty 3000 motherboard and a quick dab of the soldering iron sorted those problems.

Challenge 1: the manual is in German. Ich kann ein bischen Deutsch, aber I have forgotten so much. Thankfully, google translate fills the gaps in vocabulary even if it completely fails on the semantics sometimes – with potentially disastrous consequences! Jumpers and components that are optional or must be omitted in certain circumstances turn to merely optional in google translate…
Challenge 2: VGA output is on an 8 pin DIN connector. A quick ebay later for an 8pin connector, and I constructed a GBA1000->VGA adaptor.
Challenge 3: I want to use this with my 3000 keyboard, so I made a cable from RJ11 4p4c to DIN to go to my switchbox.

To enable the RAM, a driver needs to be loaded: this is best achieved by having the board pre-load the driver as part of the Amiga’s boot diagnostics sequence, and this option is enabled with a jumper. At the same time as loading a driver, a small intro is displayed on power up. It’s quite interesting that this happens before the early boot menu, or even before guru meditations if errant software forces a reset. Part of me wishes that the source code were available so that the intro could be personalised…  I may drop Hr Braun a mail.

The disk subsystem emulates an Oktagon 2008 IDE interface and so can be used with the TD64-aware Oktapussy driver suite. This is a Good Thing.

Anyhow, this is all preamble, how does the board perform?

In short, it’s over twice as fast as an A3000. Chip RAM access it three times that of a 600. It has more than enough power for any classic ECS Amiga duties. It supports CF cards with an IDE->CF adapter. It outputs directly to VGA monitors (at 50Hz). I can plug a Picasso II into the  Zorro2 slot and get RTG graphics (however, I need to make some form factor adaptor there, as the card is back to front and rather too high to put the case lid on).

There are expansions that have been built for this GB A1000, such as a Picasso II in a dedicated form factor. Unfortunately, my GB A1000 is a revision 0 board missing the internal connector for this, but that is not a big issue at all. There are 040 and 060 accelerators with 32MB of memory.  It really is astonishing to see the levels people have taken this hobbyist board!

Downsides, ‘Gotchas’? No Z3 bus, but Z3 is a couple of orders of magnitude up from Z2 so this is understandable. The front and Z2 expansion ports pass their config_in signals through jumpers if there’s no card on them, so those jumpers need to be treated with care. (On bus boards, a small logic chip typically routes one board’s config_out to the next board’s config_in if there’s no card present). The right hand expansion port, when I connect something to it, simply locks the computer and I can’t see why. It would have been nice to put a clockport on here whilst designing the board. But these are picky points!

The worst downside is the loss of the site, which is the project’s home on the internet. I’m trying to find out what happened there, but it seems to have just disappeared which is a great shame.

Saying all this, I like it just as it is. Together with my 3000, it’s the most used Amiga that I have and also the most reliable. It sits on a switchbox with my 3000 and 4000, connected to a 20″ LCD VGA, and works wonderfully.

Next project for it: fitting the Picasso II in a way that allows me to leave the case off!

performance 9/10
Quick for an 030 solution, great ram performance, good hard drive performance.
value 9/10
I paid a reasonable amount for a completed board, however the components would run to around $300, for which it is a good price for what you get.  Of course, compared to an ACA1230/28 it looks a little expensive, but value is subjective here!
ease of use 8/10
With an English manual it’s easier to use, however the jumper setting for expansion and tweaks required could be improved
reliability 10/10
Absolutely rock solid. Has been on soak test for 72 hours with no problems.
overall 10/10
An astonishing piece of hardware on so many levels. For the 1000, it is without equal.

Kristian Karlshoj, organiser of the group buy, made an English translation of the manual and has allowed me to share the PDF version.