PDP-8/A Miniprocessor Users Manual

This document introduces the RL01/RL02 disk subsystem, providing information on its capabilities, installation, operation, and programming, primarily for operating and programming personnel.

The subsystem comprises:

1. RL01/RL02 Disk Drives: These are physical units with internal components like a spindle, read/write heads, power supply, and air systems.
2. Controllers: One of four types: RL11 (for PDP-11 UNIBUS), RLV11 or RLV12 (for LSI-11 Bus), or RL8A (for PDP-8 OMNIBUS). All support Direct Memory Access (DMA) and can manage up to four disk drives.
3. RL01K/RL02K Disk Cartridges: These are removable, top-loading 5440-type cartridges. The RL01K holds 5.2 MB of user data, and the RL02K holds 10.4 MB. Each cartridge has a single platter with two data surfaces (256 tracks for RL01K, 512 for RL02K), and each track is divided into 40 sectors. Servo and header information are prerecorded and protected, while only the data portion of sectors is user-writeable.

Key features and operational details include:

• Interchangeability: Cartridges are physically interchangeable but generally not functionally so (e.g., an RL01K on an RL02 drive will not operate correctly).
• Sector Format: Each sector contains servo information, a header (with address, head, and cylinder details), and data.
• Rotational Speed: The disk rotates at 2400 revolutions per minute, with each sector lasting 625 microseconds.
• Data Transfer: Data transfer rates are provided for 16-bit, 8-bit, and 12-bit word modes.
• Seek Operations: The system relies on software-programmed seeks for head positioning, as there is no physical index notch. Rotational latency is minimized through sector offsets for head switches and cylinder seeks.
• Bad Sector File: Each cartridge contains a Bad Sector File listing defective sectors and the cartridge serial number, used by the operating system to avoid allocating bad areas.

The document also includes tables detailing the physical, environmental, and operational specifications of the RL01/RL02 disk drives and cartridges.