Gradiente Expert GPC-1
This page was last modified 09:17, 8 March 2023 by Gdx. Based on work by Mars2000you and Rderooy and others.



The Expert GPC-1 was the second MSX1 model made by Gradiente, which fixed some issues of the previous model XP-800 (see Specifications section). GPC means 'Gradiente Personal Computer'.

Following the release of the GPC-1 on the market, Gradiente issued a free recall called "Conversion from 1.0 to 1.1", asking to owners of Expert XP-800 to take their machines to a service center. In a few minutes the EPROM and the 9 keys were substituted, free for the user.

Because of this, most of Expert XP-800 are found showing a 1.1 ROM version and modified keyboard.

Brand Gradiente
Model Expert GPC-1
Year  ??/1987
Region Brazil
Launch price
RAM 64kB in slot 2
Media MSX cartridges
Video Texas Instruments TMS9128NL
Audio PSG
Chipset none (separate IC's)
Keyboard layout QWERTY with a "ç" key + numeric keypad
Extras built-in speaker with volume control, RGB output, demo cartridge called "Ligue-se ao Expert"
Emulation ROM dumped and emulated. The shared 2nd cartridge slot with the rear expansion port is handled like a single MSX cartridge slots.


Gradiente Expert GPC-1
XP-800 keyboard (up) and GPC-1 keyboard (down) with different keys marked
Gradiente Expert GPC-1 keyboard
Gradiente Expert GPC-1 PCB
Gradiente Expert GPC-1 back panel. Marked CONSOLE MOD. C1/I
Demo Cartridge (2 units shown)


The Expert GPC-1 is a rather complete MSX1, with full 64KB of RAM in slot 2. It has a Z80A from Zilog.

Slot Map

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


Modifications by comparison with the XP-800

Hardware Modifications

No modification was made to the digital PCB, but there are batches with IC sockets just for RAMs and LSI chips, and batches with no IC sockets at all.

The TA-1 TV adapter was embedded onto the machine case, meaning that the analog PCB was changed to provide a composite video output (PAL-M standard) and a RF output (VHF channel 3 or 4).

They also added a 6VDC supply output to power the DR-1 data recorder.

Software Modifications

The way of typing accented letters was changed to be exactly as like in a typewriter. And the codes of the Portuguese accented characters were changed to match a specification called "Brazilian ASCII", or BRASCII.

These modifications in ROM led to the version to be changed to 1.1. But this computer is known and often called by brazilian MSX users as "Expert 1.1" due to the hardware modifications.

Keyboard Modifications

Also, the positions of the accents and some characters were changed in keyboard layout, leading to 9 different keys between the layouts of the keyboard of XP-800 and GPC-1.

The issue of wearing-off the painted letters of the keyboard remained.