KE11-A — extended arithmetic element
The KE11-A is the extended arithmetic element of the PDP-11/20: a UNIBUS
card that multiplies, divides, shifts and normalizes 32-bit values for a
processor whose instruction set has no instructions for it. A program writes an
operand to one of its registers and reads the result back. QUniLator lists it as
ke, of type KE11.
What the machine sees
Section titled “What the machine sees”Eight registers from 777300. AC (the high word) and MQ (the low word) hold a 32-bit value. Writing an operand to DIV, MUL, LSH or ASH carries out that operation on it, and writing NOR normalizes it; the result is left in AC and MQ, and the status in SR.
| Address | Register | |
|---|---|---|
| 777300 | DIV | Divide AC and MQ by the word written: quotient in MQ, remainder in AC. Reads 0 |
| 777302 | AC | Accumulator, the high word |
| 777304 | MQ | Multiplier-quotient, the low word. Writing it sign-extends it into AC |
| 777306 | MUL | Multiply MQ by the word written, the product in AC and MQ. Reads 0 |
| 777310 | SC/SR | Step counter in the low byte, status in the high byte |
| 777312 | NOR | Writing it normalizes AC and MQ, counting the shifts in the step counter |
| 777314 | LSH | Logical shift of AC and MQ by the count written. Reads 0 |
| 777316 | ASH | Arithmetic shift of AC and MQ by the count written. Reads 0 |
A byte written to the low half of AC, MQ, DIV or MUL is sign-extended to a word. INIT and power-up clear every register. The card takes no interrupt.
Using it
Section titled “Using it”Enable ke on the Configurations screen. It has no settings of its own, and
base_addr moves it away from 777300.
What has been verified
Section titled “What has been verified”No DEC diagnostic is recorded as passing against this card.
Parameters
Section titled “Parameters”It has no parameters of its own.
It also carries the parameters under parameters every card on the bus has.