Doragasu started a project in January 2017 about a ROM board interface with DMA transfert. The project is now a reality :

• it can play digital audio with approximately 0% CPU overhead. The limits are the bits per sample ( 8 ) and the maximum sample length (64 KiB). Sampling rate can be configured on the fly, and ranges from 3906 Hz to 50 kHz (and beyond)
• it can can transfer data from external ROM to internal CPC RAM at 1 byte per microsecond. While doing DMA the Z80 is stopped, but this is much faster than doing the copy using software routines