Twelve different models of the 3274 are available. The suffix after the model number indicates the environment in which the controller is used.
- The "A" suffix indicates a channel-attached SNA environment.
- The "B" and "D" suffix indicate a channel-attached non-SNA environment.
- The "C" suffix indicates a remotely attached environment.
Models 21, 31, and 41 support up to 32 attached devices. Model 51 supports 12 devices, and Model 61 supports 16 devices.
Most 3274 control units are capable of supporting DFT devices. Generally, the hardware does not determine whether a control unit can support DFT. Rather, the control units' microcode software supplies the additional function necessary to support DFT. However, minimum memory requirements are necessary for DFT support. In some cases, 3274 control units may require memory upgrades to have enough memory for DFT support.
Assuming you have enough memory, MacDFT will run with the above configuration if the controller microcode is 65 or higher. In remote bisynchronous, you can run MacDFT only in CUT mode.