1. OVERVIEW
-----------

1.1 Role of the VRM
~~~~~~~~~~~~~~~~~~~

The Virtual Resource Manager (VRM) provides the hardware abstraction layer
of HyperCP/M.

The VRM presents a consistent virtual machine environment to HyperCP/M
kernel subsystems regardless of the underlying hardware implementation.

The VRM is responsible for abstracting and providing access to hardware
resources including:

  * CPU execution state.
  * Memory.
  * Devices.
  * Interrupts.
  * Timers.
  * Storage hardware.

The VRM does not provide operating-system services. Instead, it provides the
hardware model upon which HyperCP/M kernel services operate.

1.2 Relationship to the HyperCP/M Kernel
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The VRM is a component of the HyperCP/M kernel architecture.

The kernel uses VRM services to access and manage hardware resources.
Personalities and applications do not directly access the VRM.

1.3 Virtual Machine Model
~~~~~~~~~~~~~~~~~~~~~~~~~

Each HyperCP/M session operates within a virtual Z80 machine environment.
The virtual machine environment presented to a session shall be independent
of the underlying hardware implementation.

A session observes:

  * A Z80-compatible CPU environment.
  * A defined Z80-compatible memory address space.
  * Virtual devices.
  * Virtual storage resources.
  * Virtual interrupt sources.

The underlying hardware implementation is not visible to the session unless
explicitly exposed through a defined virtual device or service.

1.4 Design Principles
~~~~~~~~~~~~~~~~~~~~~

The VRM is designed according to the following principles.

Hardware Independence

The VRM shall separate HyperCP/M kernel services from specific hardware
implementations.

Kernel subsystems shall interact with virtual resources rather than directly
accessing physical hardware.

Personality Compatibility

The VRM shall provide the virtual hardware environment required by each
supported personality.

The VRM shall preserve the hardware assumptions expected by historical
operating systems where compatibility is an objective.

Resource Abstraction

The VRM shall represent hardware capabilities as abstract resources rather
than exposing implementation-specific details.

Physical resources may be implemented using different hardware mechanisms
provided that the defined virtual machine interface is preserved.

Isolation

Resources assigned to one session shall not interfere with resources
assigned to another session except through explicitly defined sharing
mechanisms.

Extensibility

The VRM shall permit additional hardware capabilities and virtual devices to
be added without requiring redesign of existing kernel services.

Minimal Assumptions

The VRM shall expose only those hardware capabilities required by the active
personality or HyperCP/M services.

Implementation details shall remain hidden unless explicitly exposed through
a defined interface.