Path: utzoo!utgpu!watserv1!watmath!att!att!bu.edu!rpi!uupsi!sunic!cs.umu.se!christer From: christer@cs.umu.se (Christer Ericson) Newsgroups: comp.sys.apple2 Subject: Re: Proposal: Apple II+ 60Hz Timing Signal Message-ID: <1990Nov1.124644.17094@cs.umu.se> Date: 1 Nov 90 12:46:44 GMT References: <5391@crash.cts.com> Sender: news@cs.umu.se (News Administrator) Organization: Dep. of Info.Proc, Umea Univ., Sweden Lines: 27 In article <5391@crash.cts.com> mdavis@pro-sol.cts.com (Morgan Davis) writes: >This is a note to fellow Apple II software developers. Recently, I've been >studying the possibility of building a small circuit that gives the Apple II+ >a 60Hz signal by which software can poll to synchronize timing loops. This >is more important now than ever since many II+'s are becoming equipped with >faster CPUs (Zip Chips, Transwarps, etc.). > >After learning about a 60Hz signal source on the motherboard, I scrapped the >idea of building a circuit using a 555 timer IC. The source is located on pin >#11 of the 74LS161 at location D-11 (the chip just right of the resistor pack). > > [Stuff deleted] Without having my old Apple II Reference Manual (the real thing - not the worthless Apple IIe Ref mind you) around, I'm not sure if this will work on all Apple IIs, there is this thing about us in Europe having 50Hz current instead of 60Hz. I'd guess that whatever the 74LS161 at location D-11 is doing might be somewhat different on the Apple II Europlus (and other european models). Someone who knows for sure? >--Morgan Davis /Christer | Christer Ericson Internet: christer@cs.umu.se [130.239.1.101] | | Department of Computer Science, University of Umea, S-90187 UMEA, Sweden | | "9600