faheyr@silver.ucs.indiana.edu (Bob Fahey <NECR0SIS>) (09/28/90)
Hi there. I tried putting in the 14Mhz hack that people are talking about here, but to no avail. I tried tapping the 28Mhz clock, & made a div-by-2 out of a D flip- flop, but I couldn't get the 14Mhz signal to work. The 7Mhz side continued to work fine, though. (BTW, it was with a 12Mhz 68000). Where does one tap the 28Mhz signal? Directly from the crystal? And, does the div-by-2 need to be synchronous or a-sync? If anyone knows the CORRECT way to peice one of these 14Mhz-er's together, please mail me! (For example, if you know how to build the div-by-2, and where to tap the signal) If this makes any difference, it is on a Rev. 5 motherboard, with (yikes!) 1.2 kickstart. Will this hack work on a rev. 7? Tanx in advance, Bob Fahey@silver.ucs.indiana.edu | ///| a.k.a. NECR0SIS oo faheyr@silver.ucs.indiana.edu -or- | | \\\ ///_| \__/ faheyr@rose.ucs.indiana.edu | | \XXX/ | M I G A | | "'Ere long done do does did..." -The Smiths |
martijn@dnlunx.pttrnl.nl (Reinalda M.) (09/28/90)
The 28 MHz signal is best tapped on pin 34 of Fat Agnus. If you sit in front of your computer, then P34 is on the upper row, the second from the right. The D-flipflop to use is the 74ALS74. Don't use a slower type, just to be sure. By the way, you should use a 14 or 16 MHz CPU or the 68000 will experience some serious timing problems. This are the FF pin connections to use : p14 -> +5V P7 -> GND p13 -> +5V p10 -> +5V p11 -> 28 MHz input p9 -> 14 MHz output p8 -> p12 Don't use wires longer then a few centimeters. If you get any E-mails or other info on this subject, please post'em next to this article so us hardware hackers can read'em too.