RH20 MASSBUS controller

An RH20 MASSBUS controller is the primary secondary storage device controller for the later KL10s (the ones with so-called 'internal' main memory). It works with MASSBUS disk drives and magnetic tape drives (such as the RP06, etc, series drives); up to 8 drives per RH20.

The RH20 is connected to both the E Bus and the C Bus of the KL10; the former to allow the CPU to control it. and the latter to give the RH20 direct access to the main memory of the system, to allow it to use DMA to move data directly from devices to main memory, without needing CPU intervention.

Implementation

Each RH20 consists of a set of three hex boards (M8555, M8556, M8557), inserted in the KL10's I/O backplane (along with the DTE20s).

See also

• RH10 MASSBUS controller‎

External links

• RH20 Unit Description
• RH2O Field Maintenance Print Set
• KL10-Based Technical Manual (EK-OKL10-TM-002) - the RH20 is covered on pp. 102-104 of the PDF; the CBUS is covered on pp. 86-90
• decsystem-1080/1090 System Description (EK-1080U-SD-003) - the RH20 is covered on pp. 77-78 of the PDF
• Tony in RH20 Land - An account of Tony Wachs adding RH20 support to TOPS-10.