Fire up the iron...

From: Christopher Zach <cz_at_alembic.crystel.com>
Date: Thu Nov 30 11:36:21 2000

The RH11 on the tape drive side is just a normal RH11. The one for the
discs is specially hacked to run in what's called "Hog mode DMA". This
is where it grabs the bus for transfers and never lets go.

On a pdp11, this would starve any other DMA device. On the 2020, the
RH11 is the only thing on that Unibus, and the 20's UBA is designed to
cache stuff coming in from the Unibus (in 18 bit chunks) and forward it
to the CPU/memory in 36bit chunks.

Chris
Received on Thu Nov 30 2000 - 11:36:21 GMT