I told David Betz I would send him a fast Lisp interpreter I wrote in Amiga assembler about 15 years ago. Now I have to get my Amiga working -- a worthwhile interruption to my PDP-11 restoration. This is an original rev 1.0 Amiga 1000 with one floppy drive, expanded chip RAM, 2 megs in a StarBoard on the side, and nothing else. It's the first computer I ever bought rather than built from scrap. It cost about $1000 in the days when an IBM AT with EGA, 1 meg RAM, and 30 meg hard drive cost several thousands, and 1.0 VAX-MIPs meant something. All the original pieces and manuals are still there and intact except for the monitor which died years ago. I'm using a small B&W NTSC monitor until I get a VGA adapter cable built. First, I tore it apart and cleaned out the dust. Pulling the cooling air in through the floppy drive was a brilliant concept. That way the cheap and replaceable floppy drive doubles as an air filter. There was very little dust elsewhere. After trying 5 Kickstart disks, I found one that would still read. I can boot the Lisp development disk, and, with plenty of patience and retries, it loads itself into the RAMdisk. So, in theory, the Lisp interpreter sources are recoverable (I also have it on 3 backup disks). The floppy drive, or something related, has a problem however. The computer cannot see when I remove a disk, therefore, it never refreshes the cache when I change disks. It never realizes that the disk has been changed. So I have the Lisp sources on one disk that will boot successfully, Kermit and CrossDOS on another good disk, but whichever one I boot, I cannot read the other. It will take a while to remember/relearn how to run an Amiga. The reed relay actuated by the floppy drive eject button is working, and there is continuity to a large chip on the drive. I'm guessing the computer is looking for "disk change" (pin 34 on the interface), which is probably triggered by the reed relay. I tried an IBM-PC floppy drive -- it boots from that drive, but still doesn't see the disk change. I tried a different ribbon cable. There is continuity from pin 34 on the mainboard floppy connector to a pin on what looks like it might be a PIO chip. There are two of these 40 pin DIPs in sockets next to the 68000. I exchanged the two chips -- that made no difference. I examined pin 34 with a voltmeter, with the ribbon cable disconnected but power applied to the drive. It doesn't wiggle when I insert and eject a floppy. But testing this with the cable disconnected might not be a valid test. It might be strobed by "drive select". With everything hooked up, I don't see a significant voltmeter wiggle on the PIO pin -- again, it might be "drive select" enabled, or polled with a very low duty cycle, so that test might not mean anything. Now that I think of it, I seem to recall that the pin was low. That sounds suspcious. I would expect if it was strobed, it would be a low-true open collector. I need to go back and look at that again. Questions: Is there some software way to force the computer to flush the disk cache and take a fresh look at a disk? Is an IBM-PC 1.44 meg floppy drive an adequate replacement for the original 800K internal drive, at least for reading? I downloaded a bunch of floppy related "hacks" from an archive (Aminet?), but I haven't had time to parse them all yet, plus I can't see the IFF formatted diagrams from a PC. Bear in mind that I have only one drive, so drive select logic might not be needed. What is the mechanism/algorithm used to detect drive change? What could have gone wrong? If I get desperate enough, I'll cut pin 34 on the ribbon cable and run it to a pushbutton dangling outside the case (assuming that pin 34 is the missing signal). -- Jonathan Engdahl Rockwell Automation Principal Research Engineer 24800 Tungsten Road Advanced Technology Euclid, OH 44117 USA Euclid Labs http://users.safeaccess.com/engdahl