PDP-8/A
Introduction
The PDP-8/A was introduced in 1974 at a cost of $1835.00 US. TTL MSI logic allowed the CPU to fit onto a single board. The KK8-A CPU (M8135) single board CPU ran at 666 KHz with a memory speed of 2.6 microseconds. Packaging was similar to the PDP-11/04 and 11/34 series of minicomputers, including the front consoles. The console flip switches and front panel lights on earlier PDP-8s was replaced by a push button octal panel and a 4 digit LED display.
The 8/A was the only 8 series computer to support more than 32K of memory using the KM8-A Extended Option. Some models shipped with 128K of memory. Other options were the DKC8-AA (M8316) front panel control, parallel port, asynchronous serial line controller and real-time clock. A floating point processor option was also available (FPP8/A, M8410, M8411). Memory options were available as core 8K (MM8-8A H219A/G649) and 16K (MM8-AB, H219B/G650) or semiconductor (MS8-A, M8311) memory. A minimum system could be run with only three cards. As with the UNIBUS backplane on the 11/04,the OMNIBUS backplane was laid out horizontally.
PDP-8/A Architecture
Source: Miniprocessor Users Manual EK-8A002-MM-002
This was the last computer model using discrete components; subsequent models used the Harris or Intersil PDP-8 microprocessor chip. The 8/A was withdrawn from the market in 1984. The market for PDP-8 systems declined in the face of customer demand for 16 bit mini and micro computers
PDP-8/A Options Summary
| Option | Description |
|---|---|
| DKC8-AA | Extended Memory Option. Extends the memory capacity beyond 32KB. |
| KM8-A | (M8316) front panel control, parallel port, asynchronous serial line controller and real-time clock. |
| FPP8/A | A floating point option was available on two cards; M8410 floating point processor control, M8411 data path card. |
| MM8-8A | 8K Core Memory. G649 core Stack and H219A core memory control |
| MM8-AB | 16K Core Memory. G650 core Stack and H219B core memory control |
| MS8-A | Up to 128K of semiconductor memory (M8417 MSC8DJ 128K DRAM MOS memory). Semiconductor memory is on one card, versus the two cards typically required for core memory. |
| KL8-A | Four channel serial controller; RS-232 or 20ma current loop option. |
| RL8-A | Controller for 1 to 4 RL01 or RL02 disk drives. |
PDP-8/A Model 400 Console
Source: Wikipedia
PDP-8/A Guides
| Document Name | Order Part No. | Publication Date | Domain |
|---|---|---|---|
| PDP-8/A Schematic Prints | MP-00415 | 1977 | HW |
| PDP-8/A Miniprocessor Users Manual | EK-8A002-MM-002 | December 1976 | USR |
- Adapted from: https://en.wikipedia.org/wiki/PDP-8