From mboxrd@z Thu Jan 1 00:00:00 1970 To: 9fans@cse.psu.edu From: "Douglas A. Gwyn" Message-ID: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit References: <29ce300d69819f673d96bbd7d9ae9302@vitanuova.com>, <016601c35353$10db3be0$b9844051@insultant.net> Subject: Re: [9fans] Re: random moving of cursor arrow Date: Mon, 28 Jul 2003 08:47:43 +0000 Topicbox-Message-UUID: 06c895a8-eacc-11e9-9e20-41e7f4b1d025 boyd, rounin wrote: > iirc, from the dz-kmc days you needed to manage the 'fifo' so it wouldn't > overrun, but at the same time you needed a timer to empty it [stick on the rawq] > so stuff just didn't get 'stuck'. No, the problem arises when people try to set the input alarm threshold at more than 1 character. In the case of the DZ11 the right thing to do was to interrupt on any incoming character and after processing (putting in the queue) wait a tiny bit for the FIFO to trickle down then test for another ready character, and if found don't return (context switch) but instead go back to the start of the intr function and process the character. My driver did that, and on a PDP-11/34 we had a couple of dozen concurrent users of 9600bpi terminals with great response. I have a KMC11B sitting around, and some day I'll look into whatever problems there might have been. The idea of a front- end processor was right, even if the implementation wasn't. > how much time have i wasted with rs-232 junk? too much. However, it's as near to universal as one can get, even today. I have a paper tape reader and an Apple IIGS attached to my PCs via RS-232-C. (The magtape is on SCSI.)