On Sat, Mar 11, 2017 at 6:10 PM, Mouse via cctalk <cctalk@classiccmp.org> wrote: >> I'm not sure about the MicroVax II but on some other VAX and Alpha >> machines, the console port may be less capable than ordinary terminal >> ports in the way of buffering, flow control, 8 bit support and so on. > > The KA630, the MicroVAX-II CPU board (which includes the console serial > port), has a relatively limited serial port. For example, it has only > a byte or two of buffering in each direction, it cannot be used > directly from userland even if the kernel wants to let it (it is > accessed with MFPR and MTPR instructions), it has no software baudrate > control, and various other limitations. > > These have concomitant benefits for console use, such as no software > setup being required to get small numbers of characters transferred. > But they do rather cripple it for voluminous data transfer. If you > have an at-least-mildly-smart serial port card (eg, with substantial > hardware buffering capability, and/or with DMA capability), you will > probably get better performance with it.
It was 8-bit clean. And did allow for connection of a printer to it, though a relatively simple one. We wound up in the end, though, not using it except in a pinch. The limitations were just a bit too much to give reliable behavior for anything other than having a DECwriter II or VT220 connected to it. We had a 4-port serial card to connect the plotter, and a few other specialty devices we needed for our VaxStation II (which had the same KA630 CPU board and a graphics board). Warner