Talk:IMP interface

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DR11C

Re DR11C. I peeked at the driver in 2.11BSD and I think it said Unibus. But it was only a brief glance. Larsbrinkhoff (talk) 10:11, 15 March 2018 (CET)

Hey, this mentions UNIBUS:

Larsbrinkhoff (talk) 10:19, 15 March 2018 (CET)

Huh? That page talks about the IMP11-A, the DEC CSS thing.
Anyway, for the SRI thing, it was possibly both, actually. What it was was an SRI board that took the bit-stream from the IMP, doing the host-IMP harware protocol ('there's your bit', etc), and converted it to words, which it shipped over a parallel interface to a standard DEC DRV11 card. I'm pretty sure the QBUS DRV11 and UNIBUS DRV11-C had the same parallel port spec, so you could probably have plugged the SRI card into a DR11-C instead of a DRV11. Since the DR11-C/DRV11 are programmed I/O, they wouldn't have had the performance of the others, which were DMA, which is probably why UNIBUS machines tended to go with the DEC/ACC interfaces. Jnc (talk) 15:55, 15 March 2018 (CET)
Sorry, wrong link. This is better:
Yes, I see now DR11-C is the name of a parallel interface. The BSD drivers use the Unibus device to talk to the IMP interface.
Here's a manual for the IMP interface:
Larsbrinkhoff (talk) 08:36, 16 March 2018 (CET)
Right. And here is the 2.11 driver:
Looking at the driver, I'm not sure I understand how it works; it looks like it might loop in the interrupt handler, reading the entire packet? Eh, not important.
Somewhere I have MOS operating system drivers for it.
Also my memory was a bit off - it was byte at a time, not word at a time. Jnc (talk) 15:14, 16 March 2018 (CET)