PERSEUS-9 homemade mobile 6502 computer

PERSEUS-9 is a die-cast aluminum housing mobile computer having dual 6502 CPU, 48 keys and 40 x 7 LED character display.

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In 2021, I built my own floating-point interpreter system on my PERSEUS-8 computer. However, this system required a serial terminal for input/output, which was somewhat inconvenient to use for programming and calculation whenever I wanted. Therefore, I have developed the PERSEUS-9, a mobile stand-alone computer that can run this system independently.
Its features are as follows.
(1) PERSEUS-9 will have a keyboard and character display on the chassis panel, which can be used to operate a home-made floating-point interpreter.
(2) PERSEUS-9 has dual 6502 CPUs, with the first CPU running the interpreter and the second CPU performing key and display I/O processing. The address mapping of the two CPUs should be the same to facilitate operation verification.
(3) PERSEUS-9 shall be a synthesis of PERSEUS-8, 6802 Serial Terminal, and Floating Point Interpreter CI-2 technologies respectively.

1. Main feature

    Figure 1 shows the external appearance of the PERSEUS-9. The enclosure is a die-cast aluminum case with external dimensions of 262 mm x 182 mm x 55 mm.

Fig.1  Appearance of PERSEUS-9

The user interface consists of a 48-key keyboard and a 40 x 7 LED character display. The display has been expanded from the 96-character display of the 6802 Serial Terminal to a 280-character display. Power is supplied externally via 5V, 3A power adapter. External Ni-MH 1.2V battery x 4 operation is also possible. User programs are backed up by the built-in battery.

    Figure 2 shows the inside of PERSEUS-9. The board has a two-tiered structure, and in this photo PB1, in which the main computer including the 1st CPU and the terminal part including the 2nd CPU are mounted, is visible. PB2, where the key switches and LED modules are mounted, is hidden underneath. The back of the enclosure has a power connecter, three D-sub connectors for the serial interface, and a 26-pin flat cable connector for the parallel interface. On the right side, the power switch, RUN/HALT switch, terminal select switch, and display reset switch are provided.

Fig. 2  Inside of PERSEUS-9

2. Enclosure

    The enclosure is a die-cast aluminum case HQ-26-18-6N manufactured by Takachi of Japan, which is used. This enclosure is designed to be waterproof and dust-proof for outdoor equipment, but this function is ignored. Although the panel has many openings due to the hole drilling process, it maintains sufficient rigidity. Figure 3 shows the drilling of holes for switches in the panel using a reamer. 3mm-thick red transparent acrylic sheet is used as the filter for the LED display part.

Fig. 3  Reaming work for enclosure

    Figure 4 shows the connector holes for the interface and the holes for the toggle switches drilled in the back and sides. Such square holes are drilled continuously with a 3mm-diameter drill, the holes are pulled out, and then finished with a file.

 Fig. 4  Enclosure backside

3. Hardware configuration

    The hardware block diagram of PERSEUS-9 is shown in Figure 5. The schematic and the parts location figure are shown in the attachment file . In Fig. 5, the left half of PB1 is the main computer part shown on pages 1 to 3 of the schematic, and the 1st CPU is IC21. This is the PERSEUS-8 without the DMA control part for address and data input by toggle switches and LEDs.

    The right half of PB1 in Fig. 5 is the Serial Terminal portion including the 2nd CPU shown on page 4 of the schematic. This is basically similar to the 6802 Serial Terminal, but PERSEUS-9 has 2.9 times more LED modules than the 6802 Serial Terminal, so the processing speed needed to be faster. Therefore, the MC6802 (1 MHz) CPU was replaced with a 6502A (2 MHz). This resulted in a 6502 (2 MHz) dual-CPU configuration for the entire PERSEUS-9. This is not a recent CPU configuration with many cores, but it is a configuration with a main CPU and an I/O CPU, which was common around 1980. The two computer parts have the same address mapping to facilitate hardware operation verification. For example, the ROM and flat cable of the terminal part can be replaced with the main part to verify the operation as a terminal.

    In Fig. 5, PB2 consists of 48 key switch matrices and 35 5x7 dot 8-character LED modules shown on page 6 and page 5 of the schematic. The data lines of the LED modules are connected in cascade. And all of these are connected to an 8-bit parallel port.

    The terminal selector in Fig.5 switches the serial data lines with toggle switch S3, as shown in the schematic page 7. When the connection is internal, the PERSEUS-9 alone can operate the interpreter via keys and LED displays on the panel. When the connection is made external, the serial lines connecting the main computer and...

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Parts location figure of PERSEUS-9

Adobe Portable Document Format - 14.32 MB - 08/11/2022 at 11:15



Example user program for PERSEUS-9 (memory dump)

Adobe Portable Document Format - 14.92 kB - 08/11/2022 at 11:12



Example user program for PERSEUS-9 (calculate Poisson distribution)

Adobe Portable Document Format - 11.45 kB - 07/23/2022 at 09:59



Assembly code of the terminal section of PERSEUS-9

Adobe Portable Document Format - 72.62 kB - 07/23/2022 at 09:57



Schematics of PERSEUS-9

Adobe Portable Document Format - 222.47 kB - 07/23/2022 at 09:56


  • 2 × R6502A Microprocessors, Microcontrollers, DSPs / Microprocessors (MPUs)
  • 3 × MC68B50 Microprocessors, Microcontrollers, DSPs / IO Controllers
  • 5 × D2716-1 EPROM
  • 3 × HM6264BLSP-10L Memory ICs / Static RAM (SRAM)
  • 3 × MAX233CPP Interface and IO ICs / RS-232, RS-422, RS-423 and RS-485

View all 14 components

  • PERSEUS-9 project log

    Mitsuru Yamada18 hours ago 0 comments

    1. The article was first posted on Jul. 23, 2022.

    2. Revised on Aug. 11, 2022

        Added the parts location figure and a memory dump program by using CI-2 in the attachment. 

View project log

Enjoy this project?



epooch wrote 07/30/2022 at 03:10 point

Another beautiful build! This enclosure is also sold under the brand name Gainta, model HQ033S in Europe or BUD IPS-3933 in U.S., if anyone is looking for it.

  Are you sure? yes | no

Mitsuru Yamada wrote 07/30/2022 at 04:23 point

Thanks for the information. Many of the aluminum die-cast cases on the market are thick-walled and very heavy at a certain size, but I was able to get one with just the right dimensions and not too heavy, so I used it for this project.

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koko484005 wrote 07/28/2022 at 04:40 point

i like this invention

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Mitsuru Yamada wrote 07/28/2022 at 04:54 point

Thank you! I have synthesized in my own way the basic technologies that are universal in the age of computer for hardware and software.

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Dan Julio wrote 07/28/2022 at 04:05 point

Spectacular, as always, Yamada-san.  Very nice build.  I like the round keys.

  Are you sure? yes | no

Mitsuru Yamada wrote 07/28/2022 at 04:47 point

Thank you for your comment!  I used many LED modules, I had to take various difficulties such as countermeasures against malfunctions caused by write signal pulses and speeding up the firmware. I think round keys goes well with the retro and futuristic design image combined with the aluminum die-cast case.

  Are you sure? yes | no

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