"Those, who are familiar with architecture and programming of MSX computers and other devices based on Texas Instrument's TMS and Yamaha's V99x8 family video processors, know that while these VDPs provide remarkable graphics flexibility and capabilities, they are not lack of serious drawbacks which are missing in the models like Commodore or Spectrum. Those issues include ported VDP access, no option for CPU to access VDP memory directly, and serious video problems when over-clocking the system (e.g. installing Z80B at 7MHz speed).
I've designed and built prototype of the Direct Video Memory Access (DVMA) board, which allows to map video memory to the CPU addressable space window, uses hardware synchronization between CPU and VDP (so no "NOP" is required between VDP access commands), and what's even more important - graphics performs excellently in the over-clocked system. It holds 128K of video memory based on fast SRAM chips.
I have taken MSX1 Yamaha YIS503IIR machine, upgraded it to MSX2: soldered some logic on board, upgraded memory board, modified and programmed MSX2 bios to work without RTC chip. This model is best suitable because it has CX7 version 1 board with VRAM memory board connector (native YIS503IIIR has main board of version 2 without such connector).
With this board, CPU command 'LD (HL),A' is enough to draw on the screen."
Let's say for standard 3.58 MHz, or 7 MHz machine. 
