Month: July 2025

Story Behind Bouncing Kamungas

During my journey to build the SmartDisk II, I made a ton of mistakes, and at the same time I learned so much, but sometimes it takes very long to sort things out. This is the story of the Bouncing Kamungas where I scratched my head. 

The initial software version of the SmartDisk II was using the SPI DMA. SPI is a common hardware interface that enables to send at a given frequency a buffer of bytes. This last word is very important and you will understand why. 

The beauty of the SPI DMA is that it is not blocking or consuming CPU resources everything is done in the back. On top of it you can configure the bytes buffer to be circular and to restart at the end forever, a bit like the floppy disk drive.

SmartDisk was loading image track to the SPI buffer, with a length and … Read the rest

Resurrecting an IBM 5175 Monitor

After a few years to inactively searching for an IBM 5170 (the holy grail), I finally found an auction on a french domestic website. And luckily enough, I was proposed 2 monitors to come with it:

  • IBM 5151 12’’ TTL Logic monochrome monitor
  • IBM 5175 Professional Graphics Display (monitor for PGC card),

Of course, the 5170 was not booting with many defects: 

  • Hard-drive failure,
  • Battery failure,
  • …

Inside the 5170, a MDA (IBM Monochrome display adapter) card was found. The MDA card is working with the 5151 monitor. 

No PGC card…

Both monitors were dusty, with spiderweb, dirty, as you can imagine with being stocked for the last 25 years… And I wanted to check if they were working. 

The 5151 was surprisingly working fine with a bright and clear green on black image. The 5170 was nicely displaying the list of error due to all the defects.

I tried … Read the rest