N.N. Thayer wrote:
On Jun 10, 3:05 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:N.N. Thayer wrote:On Jun 9, 7:52 pm, "N.N. Thayer" <nntha...@hotmail.com> wrote:On Jun 1, 9:19 am, "N.N. Thayer" <nntha...@hotmail.com> wrote:On Jun 1, 8:53 am, schmidtd <schmi...@my-deja.com> wrote:On Jun 1, 9:22 am, "N.N. Thayer" <nntha...@hotmail.com> wrote:> Hmmm. Well, now I can get to a prompt and work there indefinitely,but if I try to load anything off a disk, including ones that I know are self-bootable, I get garbage characters and the drive simply spins.I've swapped disk controller cards, and tested the drives on another machine, so I know it's not either of those.Have you swapped power supplies? Failures might be occurring because voltages drop too low to sustain life while the drive draws its power to spin up...I've got another power supply coming in the mail, a //e model.Hmm! Further testing:1. Swapping power supplies has no effect.2. If I boot a known good disk with a full onboard bank of RAM, I get garbage and a constantly spinning drive.3. If I do the same after having removed RAM E3 through E10, I get a beep and it drops me into the monitor. The drive spins down.4. If I replace E3 through E10 with RAM retrieved from a known working Language Card, and boot the disk, I get the same result as in #3.Sorry - for #4 I meant to say the same result as in #2.
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Well, what I find odd is that when I replace E3-E10 with a completely different set of chips, I get exactly the same result as with the old set - but if I remove them completely, leaving only C and D, I get dropped into the monitor when booting a known good disk. It seems unlikely to me that a chip in both sets would be failing in a totally identical way... also, when I ran RAM tests from the ][+ Diagnostics disk (back before the computer decided to not boot disks at all), it all checked out fine. Made me wonder about other chips, maybe the 74LS174's or something.
Actually, if the DOS on the disk is a "slave" DOS, then it will not adapt to the actual amount of RAM in the machine it's booted on. An Apple ][ must have "bank 0" present to operate, but I don't know which bank is in row E. You either made your Apple into a 16KB or a 32KB system by removing that row, and it would take a "master" DOS to boot on it (unless, by coincidence, your "slave" DOS matches the reduced size of the system). -michael AppleCrate: An Apple II "blade server"! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."