On 2018-08-30 10:07 a.m., James Knott wrote:
As I mentioned, I suspect this sort of thing was inherited from Unix practice, back when serial ports were common. Also, how much in the way of resources does this consume? Software designed to handle multiple devices, as was what I wrote for my IMSAI, can handle any practical number of them.
My experience with the PDP-11 and a Motoroal box that had 128 serial ports on the back as shipped was that the hardware actually did a lot of work, the UARETS were pretty smarts and the on-board hardware often had deep caches. IIR three was one PDP-11 device that had what amounted to DMA, but they called it something else. You told the board where there was a control block in memory and that was fetched by 'dma' and that also pointed to a buffer of characters. For forms/rewrite or 'cat'ing files, this was great, very little CPU load. I do recall from Dr Dobbs that some micro boards didn't have proper UARTS and did serial ports using the CPU flip a 1-bit IO port one and off with the 'correct' timing. Hellishly CPU intensive! -- "We stand behind all of our products, except for the manure spreader." -- Corporate motto of an equipment manufacturer -- To unsubscribe, e-mail: opensuse-factory+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-factory+owner@opensuse.org