The journey to Flexi Card was far from straightforward. Initially, I had no idea, and certainly no plans, to create a Flexi Card. I couldn't have anticipated everything I would need to learn, and that I would be capable of such a project.
It all started rather innocently...
A multipurpose card that emulates ROM and RAM. The ROM content is loaded from the SD card, as well as single-part programs in machine code stored in the CAS format. Below I provide a complete guide on how to make own Flexi Card.
The Sord M5 computer has a basic configuration with only 4kB of RAM, which can be expanded to 32kB using an additional cartridge EM-5. By making a small modification to the computer, the memory can be expanded up to 64kB by deactivating of the MONITOR ROM, which occupies the address space 0000-1FFFH. This modification opens up new possibilities for the computer, such as running MSX or ZX Spectrum emulators or CP/M, and so on. This modification is not something new, it was already realised in the 1980s. The modification itself involves interrupting the connection between pin 15 of the GA15 chip and pin 20 of the IC21 ROM memory , and inserting a resistor with a value between 330-390ohm, as shown in the picture. This weakens the signal from GA15 and allows for external control. The computer's functions remain unchanged by this modification, but various RAM DIY modules, including FlexiCard, can deactivate the MONITOR ROM by setting log. 1 on ROM0 bus signal.
After about 30 years, the original Sord m5 power supply started delivering unstable power levels. It stabilized at the nominal voltages a few minutes after switching on. So everything pointed to dried up electrolytic capacitors. The function of the computer was mainly manifested in the instability of VDP and video memory, where character sprites were greatly altered, image synchronization was unstable and iridescent colors ran across the image. You can see the said behavior in the video below…
Although the Sord m5 was not as popular as the ZX Spectrum, several of its clones were created during its era which spread under various names beyond the continent of Japan. Let's introduce them one by one.
Here I'm gonna place DIY guides and schematics related to the Sord hardware. Not so much now but maybe during the time another will appears....
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