anthes@geocub.UUCP (Franklin Anthes) (09/29/87)
-- oreo -- I've hooked up a philips multi-sync monitor (CM 8873) to my amiga 500. I got the description for the cable to make out of a german computer mag called 68000'er. The cable they said to make went like this : CM8873 AMIGA 1 GND 13,16 3 RED 3 4 GREEN 4 5 BLUE 5 7 CYSYNC 10 8 HSYNC 11 9 VSYNC 12 All fine and well, the only problem was that this didn't work! I tried disconnecting the HSYNC and VSYNC signals, and then the connection worked! Just for fun I tried reconnecting HSYNC and VSYNC, while disconnecting CSYNC. The result of this experiment was that the machine wouldn't boot anymore! The power light came on and that was it. But if I connected the monitor once the amiga had booted everything seemed to work fine. I tried this out friends amiga 1000, and it booted fine. Now could someone tell me : a: what video sync signals should I have hooked up to get the most out of my monitor? 1: CSYNC 2: HSYNC+VSYNC 3: both of the above b: Why doesn't my amiga 500 boot when the HSYNC and VSYNC signals are present, while my friends 1000 does fine with the same signals? And of course what can I do about it? While I'm "on the air" I'd like to send out a plea for someone to post GOFM, because it sounds like a real godsend for anybody who is doing development on the amiga. (like maybe even me:-) -- Frank Anthes-Harper Vive l'AMIGA // // \\// Usenet: ....!ucbvax!decvax!uunet!mcvax!inria!geocub!anthes Mail : 68 Pachiou-Mahos 40390 St. Martin de Seignanx France Tel. : 56-45-92-69 (don't forget to add any wierd prefixes you need to reach France)
cmcmanis%pepper@Sun.COM (Chuck McManis) (09/29/87)
In article <164@geocub.UUCP> anthes@geocub.UUCP (Franklin Anthes) writes: > All fine and well, the only problem was that this didn't work! >I tried disconnecting the HSYNC and VSYNC signals, and then the connection >worked! The Amiga uses the HSYNC line to determine if there is a GenLock on the video connector. If it has sufficient load (like it was being driven by a sync generator) KS 1.2 switches it to an input. Since the entire system is synced to this clock (and in your case it is not a clock at all) the system stops dead in it's tracks. In the video world you only need Composite Sync (CSYNC) -OR- Horizontal and Vertical Sync, not both since they provide exactly the same information. There is also an external clock input on the video connector that you can use to run the Amiga at different clock speeds. (Normally it runs at 28.xxx Mhz (8 * colorburst), and you can goose it to about 30 Mhz before things start not working correctly.) Note you must have a multisync monitor to do this since it will destroy the video timing. > a: what video sync signals should I have hooked up to get the most > out of my monitor? Just CSYNC, adding H & V Sync is superfluous. And it cuts down on RFI too to have just one sync line running out to your monitor. > > b: Why doesn't my amiga 500 boot when the HSYNC and VSYNC signals are > present, while my friends 1000 does fine with the same signals? > And of course what can I do about it? The Amiga 1000 is not mistaking the H and V sync lines as an external load. If you decide you can't sleep without hooking them up, try a current limiting resistor in line with the H and V sync lines. Start with 2.2K and go down until the 500 wont boot anymore. > While I'm "on the air" I'd like to send out a plea for someone to post GOFM, >because it sounds like a real godsend for anybody who is doing development on >the amiga. (like maybe even me:-) Actually a better Godsend is metascope, even if you don't like to use it. Run Metascope programname and if the system traps to one of the GURU addresses it will (like illegal instruction, or address fault) it will jump into metascope and you can look around. If it hits something like 'corrupt free list' you'll want to reboot anyway so why bother no? --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.
grr@cbmvax.UUCP (09/30/87)
In article <164@geocub.UUCP> anthes@geocub.UUCP (Franklin Anthes) writes: > > I've hooked up a philips multi-sync monitor (CM 8873) to my amiga 500. > > I got the description for the cable to make out of a german computer mag > called 68000'er. The cable they said to make went like this : > > CM8873 AMIGA > 1 GND 13,16 > 3 RED 3 > 4 GREEN 4 > 5 BLUE 5 > 7 CYSYNC 10 > 8 HSYNC 11 > 9 VSYNC 12 > > All fine and well, the only problem was that this didn't work! > > I tried disconnecting the HSYNC and VSYNC signals, and then the connection > worked! > > Just for fun I tried reconnecting HSYNC and VSYNC, while disconnecting > CSYNC. The result of this experiment was that the machine wouldn't boot > anymore! The power light came on and that was it. But if I connected the > monitor once the amiga had booted everything seemed to work fine. > I tried this out friends amiga 1000, and it booted fine. > > Now could someone tell me : > > a: what video sync signals should I have hooked up to get the most > out of my monitor? > > 1: CSYNC > 2: HSYNC+VSYNC > 3: both of the above > > b: Why doesn't my amiga 500 boot when the HSYNC and VSYNC signals are > present, while my friends 1000 does fine with the same signals? > And of course what can I do about it? The HSYNC and VSYNC pins are acutally input/output pins that can be used as sync/reset inputs in genloc mode. As a result they are not externally buffered, and are not really intended for driving heavy loads or cables. If your monitor supports CSYNC, then this is the best choice. If it only supports separate syncs, but doesn't work with the Amiga, the first thing to try is putting a resistor in series with the HSYNC and VSYNC pins. Values from 100 - 470 ohms have been known to work nicely. If this doesn't work, you need to build a little buffer circuit. The A500 uses the vertical sync signal for the internal clock while the A1000 uses a line-frequency signal from the power supply. In either case the computer will not boot if the clock signal is screwed up. -- George Robbins - now working for, uucp: {ihnp4|rutgers|allegra}!cbmvax!grr but no way officially representing arpa: out to lunch... Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)