MB03+ Ultimate will be a classic ZX Spectrum interface connected to edge connector. My goal is to create an interface based on modern FPGA and other chips compatible primary with it's predecessor MB02+ and others interfaces later. It's still in progress of development.


  • Z80 DMA, MBIDE, TurboSound, SAA1099, SounDrive/Stereo Covox/Specdrum, K-mouse implemented to FPGA.
  • CF and microSD cards socket.
  • MB02+ compatible memory addressing and expanded addressing to new BS-DOS (8KB pages)
  • 8MBytes SRAM, 2MBytes SPI FLASH
  • RTC DS3234 - extremely Accurate RealTimeClock with SRAM (possibility use as bios config) - full compatible with RTC72421 due to FPGA (ports, regs, etc.)
  • no FDD, no 8255 PIO on mother board
  • ULAplus compatible - no ports collision , FADI compliant, use with all ZX Spectrum (ZX 128+2 recommended)
  • WiFi ESP8266 - wifi module
  • BSDOS308 compatible
  • powered by ZX Spectrum


  • support for Residos and ESXDOS.
  • GeneralSound all in FPGA
  • DivIDE and DivMMC all in FPGA,
  • Diskface, D40/D80, Beta disk memory support
  • WD2797A Floppy Controller on kid board


LMN128's Diary

2019/01/17: Heart of new board v2 (PCB) MB03+ Ultimate. Xilinx Spartan 7 XC7S50. Quantum leap from Spartan 6 XC6LX9. There i missed pins on v1 i decided to move Spartan 7 series. It's more modern and choice bigger package with 484pins! It's enough for future and up-gradable to XC7S75 or XC7S100.

2019/01/14: The project of MB03+ Ultimate is still in huge progress. I am working on new version 2 of board with Xilinx Spartan 7 FPGA. In same time testing interface with different ZXS hardware and making specification of memory, port and mapper. New mapper will be very powerfull. Thanks help to Busy, Velesoft, Hood, Lanex and Miguel for cooperation. Lanex promise implement MB03+ to his emulator.

2018 Christmas: I started working on next version of board. I decided to use most modern Xilinx Spartan 7 and pure USB chip FT2232HQ. I am thinking to add HDMI output as well.

2018/12/22: I added new Docs tap to this page. I will put there some useful things for fan. First there is Eagle schema and board of PreciBus expansion board

2018/12/21: Example of music and sound capabilities of MB03+ Ultimate. SATELLITE by Akio Tenshi and TDM. Music for 3x AY chip. MB03+ Ultimate offer these others: Turbosound, SamCoupe SAA1099, ULA beep output, Covox (D/A), SounDrive(D/A).

All is mixed to one stereo output.

MB03+ Ultimate has implemented four 8bit DigitalAnalog converters compatible with SounDrive. This is very nice, high quality 4 channel digital music from FlashTracker. All only on 3.5MHz. Amazing! One of best digital music on ZX Spectrum by my opinion.

2018/12/17: I prepared some surprises for fans of MB03+ Ultimate to first presentation. First was implementation of ESXDOS, second was brand new firmware.

2018/12/15: Welcome ESXDOS to MB03+ Ultimate!!! This is not common ESXDOS. This is DMA ESXDOS!!! Data transfer with microSD is very fast. 4T cycles per byte. It was presented first on JHCon 2018. Thanks a lot to Miguel Guerreiro from Papay Dezign for cooperation. I am looking forward to new version.

2018/12/13: I am going to Czech ZX Spectrum JHcon party. There will be first presentations of MB03+ Ultimate. I am wonder how many people will be interest on in.

2018/12/03: RESIDOS by Garry Lancaster works on MB03+ Ultimate with microSD card!!! Thanks again Garry. Many thanks to Mario Prato and authors of ZXMMC. I was inspired by their implementation. Next step is ESXDOS!

2018/12/01: I implemented SPI microSD interface and now is possible to use both card CF and microSD. I got special version of Residos from Garry Lancaster using MB memory and SD cards. Thanks a lot Garry. I will test it asap. I spoke with Miguel from Papaya Dezign - author of ESXDOS as well. There is possibility to make special/advance version for MB03+. We will see, but first i want to run ESXDOS and Residos.

2018/11/08: I am working on basic firmware for MB03+ Ultimate and testing HW. ZXS128+2A has different way to work with video ram and uses /WAIT signal to pause CPU. I change DMA behaving to works with +2A/2B/+3. It works now. Many thanks to Ben Versteeg for ZX-HD. It works well with MB03+,

2018/10/23: Development is still in progress. MB03+ Ultimate works all independent from MB02+ now. SRAM works very well. I made another timing improvement of DMA implementation and now all DMA demos works like with original Z80 DMA chip. Finally with Omega's DNA demo. It's rather more sensitive to right timing.

2018/10/02: New World Record. ZX Spectrum with 8 Mega Bytes RAM! I got it to work on MB03+ Ultimate a made first test by run original MB02+ boot loader. This my loader is 23 years old. Unbelievable.

2018/10/02: After one week hard work i have implemented DMA to FPGA. I had to leart VHDL, because i got zxndma source code from Victor Trucco. I stopped coding my own DMA implementation and adjust and correct zxndma to works with real ZXS a MB03+. There was some timing differences, small bugs and other. There is still a lot of things to improve, but the main features are done.

2018/09/21: The v1.0 is finished finally. The soldering was rather demanding. I tested all from v0.0 and works very well.

2018/09/12: Routing is finished. The board 06- MB03+Ultimate v1 is going into production. Besides others i finally add support for Wifi module ESP8266. Internet is coming to MB03+ Ultimate.

2018/09/3: I have finished development of scheme of next test board. Next step is build board.

2018/08/31: I am hard working on next test board. It tooks me more time than i expect. I added 8MB SRAM, micro SD and USB sockets to it.

2018/08/24: I am chatting with Mario Prato, author of divMMC. It looks good. He promised send me source code of Xilinx.

2018/08/11 : I bought SD micro to CompactFlash adapter. It works very well. There is no speed problem. It will be good to find what is inside and use it in MB03+ Ultimate or implement it inside FPGA.

2018/08/10 : I have started the work on next board. Almost things are tested and current board v0.0 filled it's purpose.

2018/08/10 : I discussed with Andrew Owen about ZXI standard yesterday. I din't hear about it before. It's good idea. Finally he allocated 8 ports from ZXI range for MB03+ Ultimate purpose. Range is #203B to #273B. https://faqwiki.zxnet.co.uk/wiki/ZXI_standard.

2018/08/9 : I have soldered and tested RTC. I only implemented it as binary clock. It's enough for now. More on next test board.

2018/08/8 : Today is the day. 8/8/2018 , around at 8:00 I will say about MB03+ Ultimate to my friends.

2018/08/6 : I got the final logo. Many thanks to my friend Sharks (Zbynek Krajca).

2018/08/05 : I couldn't wait and added SounDrive, Stereo Covox and Czech Digital/Analog converters. I remembered my unfinished sound card MonsterBlaster. It was practicaly 8channels 8bits sound board. I have to find the scheme....

2018/08/04 : I am starting to work on RTC. I have chosen DS3234. It's rather big, but I think it's going to be very good.

2018/07/30 : I love General Sound and NeoGS. I re-soldered socket to Preci-Bus. I'm listening to some GS songs and I'm enjoying it. I'm also watching my older video.

2018/07/26 : I need a break but I am still working. I added Turbo sound! I must say the simulation model MikeJ's YM2149 from Jan 2005 is very good. I compared it with real AY-3-8912 in ZXS128+2 i don't hear a difference. Very good work MikeJ. I improved audio mixing to ACB stereo support. I can play SAA1099, TurboSound and ULA Beep. I like music.

2018/07/25 : I improved IDE implementation a bit and tested a lot of CF cards. All works on 3.3V. Both old and new.

2018/07/23 : CF - IDE works. It was harder than I expected, but it works very well.

2018/07/17 : I have started to work on implantation of IDE interface.

2018/07/17 : First test of MB03+ Ultimate v0.0 (04 board) together with it's older sister MB02+. No interfacing problem. This is my first board with 4 layers.

2018/07/13 : I decided to use new sockets for connecting ZXS peripherals including MB03+ Ultimate. Preci-Dip is high quality. I have improved my ZXS 128+2 and made ZX bus expander (05 board). Everything fits in perfectly . I call it Preci-Bus.

2018/07/12 : My ZX 128+2 needed ULA socket improvement for a long time. A lot of testing caused damage original socket. The worst was that ULAplus spreaded out pins and original ULA had a problem to fit it.

2018/07/09 : No more soldering wires. Finally the first test board connected directly to ZXS. Code name: MB03+ Ultimate v0.0

2018/06/26 : I made a MBIDE40 Compact Flash IDE interface (03 board) for practice with Eagle and for work and testing 3.3V CF cards.

2018/06/25 : First success. Interfacing of the 02 board looks good and due to it I implemented ULA Beep and SAA1099 (Sam chip) and it plays. WOW. Thanks a lot Miguel Angel Rodríguez Jódar for help and explanation about implementing the SAA1099.

2018/06/21 : Second interface 02 testing board done. But I still have to solder the connection wires. After that the board will be ready for testing audio output if interfacing will work.

2018/06/10 : Damn it. It seems every ZX Spectrum has different signal levels. It depends on the CPU brand/technology, PBC and others.

2018/06/06 : I am starting to test and measure of ZXS to FPGA interfacing. I have made the first 01 test board for this purpose. I have decided to use 3V3 Xilinx Spartan 6 FPGA. I have to solve the interfacing.

2018 May : I playing with FPGA. It's very cool. The possibilities are huge.

Spring 2018 : I am starting to learn Verilog, FPGA, Xilinx, Autocad Eagle, etc. So I am thinking about the best way to practice it and today I came up with an idea to make something for ZX Spectrum. So I told myself why not make a better, more modern version of MB02+. The development of MB03+ Ultimate begins!!!