Thursday, 21 December 2017

Interview with Gideon Zweijtzer from The 1541 Ultimate and Ultimate C64

Last Saturday December 17th I was in Maarssen(NL) for the bi-monthly gathering of the Commodore and Amiga enthusiasts. It was busy, as it always is in December.

Gideon was there also and presenting his debugged Ultimate C64. He is really a nice lad and down to earth.
After taking some pictures I chatted with him. As it was rather noisy and I wanted some good answers, I asked him if it was Ok for him if I could sent the questions by mail, so he could take his time and answer them when he had the time. The good lad he is, he said to me:"just ask me now". 👍 I told him that it was quite lengthy and I wanted him to answer when he was relaxed.
So here are the questions and his answers translated from Dutch to English, Enjoy!

A nice down to earth lad!
How did you end up with the C64?  
Mainly due to the enthusiasm of my brother, who started programming on the ZX81 and later on the C64 and C128. Because he is almost 7 years older than me, I was relatively young when I learned about programming. I was about the age of 8 when I started.  

Where does your passion for electronics and C64 come from?
Electronics: I find the practical side of the techniques very nice, and it fits well with my interest in computers and programming.  When I was 11, I got my first own computer; that was also a C64, because I already learned a lot about it through my brother. Now that I had one for myself, I also had more opportunities to experiment with creating programs. Later I also soldered small things together and hung them on the C64, such as a temperature gauge.

Did you made any programs on C64?
Yes. Never very big constructions, but I have made a number of programs, including a program for my father, to search for articles. My program could then index and search on a floppy.
Furthermore, I re-engineered Giana Sisters, and created new levels together with two friends, and thus released an unofficial Giana Sisters II via a local BBS in the neighborhood.  

Which programming tools do you use on the C64 and PC?
On the C64 actually none, other than the built-in tools in a cartridge, for example the monitor in the Retro Replay.
For the PC, see question below.

How did you come up with the idea for the 1541 Ultimate?
Actually, I was already working for a while to rebuild parts of the C64. Then Jeri Ellsworth came with her C64 implementation (later C1). I did not feel like playing the "me too" game, so I thought: I'll re-implement the 1541 drive. I already had a reasonable implementation of the 6502, so it was not really that difficult. Then I had to puzzle out how the floppy images would be sent to this emulator. At the very first demo of the 1541 emulation a floppy image (.d64) had to be sent via Ethernet from a PC. That was not very practical. Then the idea arose to create a selection menu that ran on the VIC itself. To this end, I tried to 'take over' the VIC via the cartridge port and DMA. It worked. In the end, a colleague did not think it was a good idea, because they had to 'sacrifice' the cartridge port for this purpose. He had a point there. Then I decided to also emulate two cartridges, the FC3 and the Action Replay, in order to eliminate this "drawback" of an occupied cartridge port. This proved to be a success!

When did you start the 1541U and when was this done?
Somewhere in 2006 I had the first floppy emulator in FPGA, and in 2007 the first Ultimate prototype came as a cartridge. At the end of that year, the production of the first Ultimate generation was started.

How much time did you put into the first 1541U?
I really have not kept that up.

Which tools do you use for this?
On the PC I mostly use Eclipse as a programming environment, but of course many other tools, such as 64tass to convert assembly code into a binary for the C64. And of course the compilers for the embedded soft cores that run in the Ultimate.

Anyway, there are also many other tools that I use for the hardware, and for FPGA design there are also several tools that I use, including a simulator (Modelsim and Aldec Riviera). And then of course there are the vendor-specific environments of Xilinx and Altera that I use to build the FPGAs.

The most recent is the 1541U2+, how do you explain the evolution from 1541U to the 1541U2 and to the present 1541U2+?
The most recent is the U2 + indeed. The U1 had some caprices, was not properly maintainable in terms of code, and was not great in terms of production, so I started again. I also thought it would be necessary to have a case around the PCB. That is how the U2 originated. I have produced these for a number of years, until the factory of the casings lost the injection mold for the second time. Also the FPGA of Xilinx suddenly became considerably more expensive, because this type came to the end of its life cycle. This was the time for an upgrade. The U2 + was created, with a new and better housing and a FPGA of a more recent family.

What functionality differences exist between these 3 generations?   What are the differences in hardware such as the FPGA?
There are too many differences to list them in detail. The U2 + has a somewhat larger FPGA, of Altera (now Intel), of the type Cyclone IV, while the U2 has a Xilinx Spartan 3A. The U2 + also has standard Ethernet on board, a speaker for the drive sounds, and an analog audio out- AND input. The audio output is of much higher quality than that of the U2. More USB ports, too.

How did you come up with the idea for ​​the Ultimate C64?  
I had this idea for quite a long time. I once gave a demo of a Commodore 64 in FPGA from my hand, sometime in 2011 or 2012. I only had the idea that this would never be feasible to take it into production, because of the board's price. The whole idea ended up in a box in the attic, and I did not do anything with it anymore. But, it turns out that the quality of the real C64s is deteriorating. I notice this with more and more problems with the Ultimate cartridges that are actually caused by failing old hardware. In order to let the C64 live on, I thought it was worthwhile at some point to get rid of the layer of dust from the project of a few years ago. And, ... by solving some things a bit more cleverly, and with more experience in terms of production and purchasing it has become feasible. Of course, the experience with the U2 + also helped to create a solid design.

Since when did you start this and what are the number of man-days that you have spent on this (women's days included ;-)   )?
I do not keep this, sorry.   I started the new hardware design at the beginning of this year (2017). Anyway, it went with ups and downs. Sometimes it was quiet for a few months. Around August I had the first prototypes, I started testing, measuring and debugging, and now, in mid-December, I can finally say that the first batch of U64s is in production. In technical terms: the zero series.

I suspect that the FPGA is different from the 1541U2 +. Can you describe this more please?
The FPGA is indeed different. The U64 uses one of the members of the Cyclone V family of Altera / Intel, while the U2 + uses a Cyclone IV.

A tentative release date for the UC64?
I expect that at the end of January 2018 the first 100 pieces will leave the factory.

Did you use other tools for the UC64 than for the 1541U2+? Explain please.  

No actually not. Just a good editor for the VHDL code (Eclipse), and a good simulator. For the U64 I have measured a bit more on a real C64. Of course, I built all kinds of tools for myself to verify what I had made. I have the most fun when figuring things out myself, and I have certainly not neglected on the U64.

Do you want to share something with the group?
Euhm .. I cannot think of anything in 1, 2, 3 .. Oh, yes, maybe. There is a new website in the making, which makes it easier to order / pre-order the U2 + and the U64. I have received a lot of questions in the past about the ordering process, and I hope that with the new website it will be immediately clear. As soon as the website is opened, I will announce this on Facebook, and also link it from the old website.  

This conludes the interview. Please leave a message if like the blog or just want to share your view on the subject 😉
Bye for now and till next time 😊

Update 20171226
Read more about Gideon's projects on his websites
Please  take into account that the latter website maybe under construction!


  1. great job! i would be interested what does he think about the mega65 project

    1. I'll ask him as soon as I'll have the occasion :)