This document contains definitions for:
1x is the 894 KHz CPU Clock rate equal to the native rate of the
CoCo 2.
2x is the 1.788 MHz CPU Clock rate equal to the native rate of the
CoCo 3.
3x is the 2.682 MHz CPU Clock rate equal to the clock rate of a
GINEx equipped CoCo 3.
4x is the 3.576 MHz CPU Clock rate equal to the clock rate of Sock
Masters double speed CoCo 3.
8x is the 7.152 CPU Clock rate equal to the maximum rate of the
Matchbox CoCo.
CoCo 3
The Tandy Color Computer 3 was sold by Radio Shack between 1986 and 1991.
Backwards compatability with this computer is a Major goal for both CoCo 4
and CoCo 5 projects.
CoCo 4
Many attempts have been made to create a "CoCo4" but from my
point of view at a minimum a CoCo 4 must
include:
- A 6309 Compatible CPU clocked at 7.152 MHz or at legacy (1x,2x,3x
& 4x) rates for backwards compatibility.
- All Standard CoCo compatible ports with enhancements:
-> Joystick Ports using an 8 Bit DAC.
-> Bit Banager Port with special 230 kb/s mode.
-> Cassette Port doubbeling as a 12 bit Audio Dizitization
Port.
-> Composite Video out of higher quality and stability similar
to Amaga Composite Video output.
-> Audio out replaced by Stereo Audio Out through a 3.5 mm
Jack
Except for the TV and RGB out ports.
- VGA or better video monitor support.
- One High Speed 920 kb/sec DB-9 Serial Port.
- At least One Meg of RAM and support for an additional 512K legacy CoCo
memory board but preferably simply 2 Meg.
- Enhanced Video at least equal to the GIMEx.
- Directly comparable with a CoCo 3 keyboard but with a way to access
Function keys 1 through 10.
- A system for updating system ROMS from a PC or Phone through one
of either a USB port or Bluetooth.
- A Fully compatable Coco Cartridge Slot for adding GAMES, HARDWARE or a
Multipak.
- Two Bluetooth Channels with support for
-> Keyboard
-> CoCo Net
-> Bluetooth Serial Port supporting up to 460 kb/s.
- Enhanced Sound
- Software Support in the BASIC 4.0 ROM and in OS-9 for these new
features.
CoCo 4 Plus
Additional new features such as support for:
- CoCo5 Keyboard with Software supporting Macros in both Basic and OS9
available as an option.
- 4 MB RAM included and supported by the enhanced MMU-H addressing
system.
- 256 KB of NVRAM allowing for Saved Settings and a
persistent 160K virtual single sided 35 track disk.
- Software to support for using the additional 2 MB to support uDisk and
vTape drives.
- Dual Monitor support in NitrOS9 allowing the secondary monitor to
monitor a fixed window for example /w7 while the main monitor shows the
current focus chosen by the [CLEAR] key.
- Add audio support for the two Bluetooth Channels with support for
-> Sterio Sound
-> Microphone
CoCo 4 Plus Plus
Additional new features beyond the CoCo 4+ such as support for:
- A Second Virtual 6309 with up to 1 Meg of RAM ( 512K Shared and
512K of it's Own. ) totaling 4.5 Meg Total.
- Dual Monitor support in NitrOS9 allowing the secondary monitor to
monitor a fixed window for example /w7 while the main monitor shows the
current focus chosen by the [CLEAR] key.
-
Support for resolutions up to 720x1280 on SVGA Monitor and 640x480 on
composite.
- USB 1.1 for updates and system mouse.
- ROM Select Switch must be set to 4 to edit settings or do updates.
- RESET button must be pressed with the USB transfer cable attaching the
system to a PC to load new settings or initiate an update.
MMU
An MMU is a Memory Management Unit the MMU in a computer allows a CPU to
use more memory than it's natural address space.
For example in the case of a CoCo3's the 6X09 CPU has a natural address
space of 64K but the GIME - MMU unit allows it to address
up to 2 MB or RAM. In the case of the CoCo5 each of four virtual CPU's can
address 2 MB of RAM in Standard Mode, one of these
virtual CPU's ( CPU#0) can address up to 8 MB of RAM in eXecutive Mode
another of these virtual CPU's ( CPU#1) can address up to
4 MB of RAM in Hardware allocation Mode and Four other CPU's #4 --> #7
may have there base address set anywhere above the low
8 MB of the 32MB of RAM GIMMEx32 accessible RAM but will get no direct MMU
services beyond this direct address translation from
the GIMMEx32 these CPU's
MMU-A
MMU-A is the standard memory management scheme that the Tandy Color Computer
3 used.
It works by selecting eight , eight killobyte blocks ( pages ) , which are
mapped into the 8 ( page frames ) accessible by a 6X09 processor.
This setup allows each CPU to use up to 2 MB of memory.
One Difference in the CoCo 5 implementation of MMUA is that the numbering of
the memory pages is relative to each CPU and the actual addresses come
from not necessarily overlapping parts of the GIMMEx32's 32MB address space.
Click here for a detailed example.
MMU-X
Is the memory management scheme that CPU #0 uses to allow it access to up to
8 MB of the GIMMEx32's 32MB address space. It is one of two MMU modes that
CPU#0 can access the other being MMU-A.
Click here for a detailed example.
MMU-H
MMU-H is the memory management scheme that CPU #1 uses to allow it access to
up to 4MB of of the GIMMEx32's 32MB address space.
Click here for a detailed example.
CoCo RED Is a virtual color computer 3 ++ runing on virtual CPU #3
that may be assigned anywhere from 128KB to 2MB of RAM and be clocked from
1x to 8x.
CoCo GREEN Is a virtual color computer 2 ++ runing on virtual CPU #2
that may be assigned anywhere from 64KB to 2MB of RAM and be clocked from 1x
to 8x.
CoCo Blue Is a virtual color computer 3 ++ runing on virtual CPU #1
it is only available when the system is in Tri-CoCo Mode and has 512K of RAM
and be clocked from 1x to 8x.
Virtual CPU The CoCo 5 FPGA emulates a system where Four 6309 CPU's
share resources primarily through a system of hardware and memory management
coordinated by a custom 32 Bit GPU chip the GIMMEx32.
GIMMEx32
Screen Layers
TL TOP Layer covers up all other layers may be
assigned a transparency to allow all of another layer to partial show
through and may
also have an assigned
transparent color which allows the layers below that "color" it to
completely show through.
ML MID Layer covers up the two layers below it
may be assigned a transparency to allow all of another layer to partialy
show through
and may also have an assigned transparent color which
allows it to completely show through.
BL BASE Layer covers up the layer below it may be
assigned a transparency to allow all of another layer to partialy show
through.
and may also have an assigned transparent color which
allows the layer below that "color" it to completely show through.
BG SYSTEM BACKGROUND LAYER is a 10 bit layer
using one of three color sets Red, Green or Virtual or a 7 bit Grayscale
set.
Sprite Layers
There are Seven Sprite Layers there location with
respect to the Screen Layers is illustrated in the following
diagram.

GIMMEx32 Color Sets
Red Set 10 bit Color set
four bits red three bits green and three bits blue RRRRGGGBBB for Background
Screen Only.
Green Set 10 bit Color set three bits four
bits green and three bits blue RRRGGGGBBB for Background Screen Only.
Virtual Set 10 bit Color set colors produced via a
more complex method to mimic grandfathered color sets.
Grayscale 5 bit gray scale set
actually a subset of the Virtual Set.