Gradiente Expert DDPlus
This page was last modified 16:08, 3 November 2021 by Mars2000you. Based on work by Rderooy and Gdx and others.



The Expert DDPlus was the last MSX1 computer released by Gradiente. Compared with the Expert Plus, the built-in firmware has been removed and replaced by a 720KB 3,5" floppy disk drive.

And compared to Expert GPC-1, a reset button has been added, while RGB and bus expansion connectors have been removed. Main Ram slot changed from slot 2 to expanded slot 3.0.

Brand Gradiente
Model Expert DDPlus
Year 1989
Region Brazil
Launch price
RAM 64kB in slot 3-0
Media MSX cartridges, 2DD floppy disks
Video Toshiba T6950, Texas Instruments TMS9918 compatible (Integrated in MSX-Engine T7937A)
Audio Toshiba T7766A, General Instrument AY-3-8910 compatible (Integrated in MSX-Engine T7937A)
Chipset Toshiba T7937A
Keyboard layout QWERTY with a "ç" key + numeric keypad
Extras 720kB 3,5" floppy disk drive, built-in speaker with volume control, reset button
Emulation ROMs dumped and emulated


Gradient Expert DDPlus
Gradient Expert DDPlus - keyboard
Gradient Expert DDPlus - back
Gradient Expert DDPlus - box


The Gradiente Expert DDPlus is a MSX1. The Z80A, the VDP and the PSG are integrated in MSX-Engine T7937A.

The integrated VDP is the Toshiba T6950, which does not support some undocumented features of the Texas Instruments TMS9918, TMS9928 and TMS9929 VDP's.

The RAM is in slot 3-0, what has been source of trouble for some programs written for the two first Gradiente computers.

Slot Map

Slot 0 Slot 1 Slot 2 Slot 3-0 Slot 3-1 Slot 3-2 Slot 3-3
Page C000h~FFFFh Cartridge
Slot 1
Slot 2
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM Disk ROM
Page 0000h~3FFFh