Hacking the GRiD GridCase 1520 and 1530

GRiD Laptop Collection, 1998

I’ve been interested in GRiD Computers for some time now. This was my collection of GRiD laptops in 1998.

In more recent years I’ve become interested in the inner workings of these machines and began a deep dive in 2019.

Find GRiDCase 1500 series specifications in the Vintage Computer Library.

Topics I will be expanding upon…

Mainboard Pinouts GRiD MS-DOS
Storage Backplanes BIOS Patching
BIOS ROMs Video Modes
Application ROMs Display Types
Adapting a Standard Floppy Drive Power Sources
GRiDCase 1520 with modifications made during reverse engineering.
GRiDCase 1520 modified with an offboard ZIF ROM socket that enables the use of FLASH EEPROMs and a custom backplane replacement PCB with IDE, Floppy, and ISA slots.

Here’s a picture of one of my test rigs that’s been the heart of my studies.  It’s a plain GRiDCase 1520 286 with CGA gas-plasma screen. 

Some modifications I made are as follows.

  1. Regular floppy drive modified to work in the GRiDCase computers.
  2. Homebrew ‘offboard’ AppROM adapter which allows the use of Flash EEPROMs instead of regular EPROMS.  This makes testing custom ROMs much faster and more convenient.
  3. Homebrew backplane replacement PCB with IDE, Floppy, and power connectors.  It also has an ISA header onto which I plugged an Olivetti ISA riser board.  This was a proof of concept, the computer can’t be closed up with the riser board in place but I’m working on a revision that can.
  4. CF card with IDE adapter to replace the hard drive.
  5. BIOS I custom patched to support CF-Cards in the GRiDCase 1520 and 1530 computers including geometry and fixing the Phoenix high speed drive access issues.  RomBuster includes the project samples and instructions to replicate this.
GRiDCase 1520 with homebrew backplane replacement and ISA riser card.
GRiDCase 1520 with homebrew backplane replacement and ISA riser card. Sound Blaster Vibra16 sound and POST cards installed running the Sound Blaster configuration and demo application. (4/26/2020)

I tested the ISA slots with sound cards and a VGA card.  The photo above shows a Sound Blaster Vibra16 installed and working.  Also installed is a diagnostic POST card but the codes shows aren’t actually POST codes.  The white paper is just to insulate things from touching.  Another revision is in the works that should fit inside the closed chassis and hold one small ISA card and have a CF-Card slot to replace the hard drive.

GridCase 1520 & 1530 series chassis 3D model for fitment.
GridCase 1520 & 1530 series chassis 3D model for fitment (2022 ClassicBits.net)

Other things…

  • MonoSol is a tiny Solitaire game written to look nice on the GRiDCase utilizing the high resolution 640×400 monochrome video mode.