PDP-8/L

PDP-8/L
PDP-8/L from an ICS Astrotype system
Year Introduced:	1968
Form Factor:	minicomputer
Word Size:	12
Logic Type:	TTL
Design Type:	clocked random logic
Clock Speed:	312KHz
Memory Speed:	1.6 µseconds
Physical Address Size:	8KW (requires optional MC-8/L)
Virtual Address Size:	4KW
Memory Management:	none
Bus Architecture:	positive logic I/O bus
Operating System:	TSS/8
Predecessor(s):	PDP-8/I
Successor(s):	PDP-8/E

The PDP-8/L was a effectively a cost-reduced version of the PDP-8/I in the PDP-8 line; it apparently had the same CPU as the -8/I.

The primary differences between the two are:

• The -8/L was slightly slower
• The -8/L used a positive I/0 bus, not negative
• The -8/L was not pre-wired for a number of devices
• The -8/L could not accomodate the Extended Arithmetic Element
• The -8/L supported a maximum of 8KW of main memory

Options for the -8/L included:

• DW08-A Negative I/O Bus Interface, to allow use of older PDP-8 devices
• MC-8/L Memory Extension Control, bank switching needed to support more than 4K words of memory
• MP-8/L Memory Parity

The MC-8/L differed from the MC-8/I of the PDP-8/I in that the Instruction Field and Data Field registers were only one bit wide, not three bits as in the MC-8/I.

It could perform an addition to the accumulator in 3.2 µseconds, and a subtraction in 6.4 µseconds.

External links

• PDP-8/L - Original PDP-8/L documents
• PDP-8/L-Maintenance-Manual-Volume-1 - Maintenance manual.