Z80 / Z84C Swap (Doh!)

Howdy Eric, Always a pleasure to hear from you! The Zilog P/N of the chip is "Z84C0008PEC", and it's further marked "Z80 CPU" with a datecode of "8904" - April of 1989? In the interim, I've pulled that chip from the Osborne and replaced it with the 'proper' Z80 from a Timex / Sinclair 1000; I did not record its markings, other than to note that it was produced in late 82, if I recall. The system now behaves better, but issues remain as follows: Started up +sans-KB+, the machine made a slight 'chirp' and a clean display came up with a message to the effect of "Insert disk in drive A and press RETURN". I attached the KB and restarted the machine. This time, the display came up with the same message, but there was something going on with the video.. it was quite flicker-y, with (scanline?) artifacts cruising around the screen. I placed a disk in Drive A and upon pressing RETURN the display immediately stabilized and went into a loop printing "BOOT ERROR" on successive lines, eventually scrolling the original boot message off the top of the display. It did not seem to even attempt seeking the disk - and it behaves the same way, whether or not a disk is in Drive A. Tried this routine several times, with minor alterations, and always the same - straight to the BOOT ERROR scroll and no other activity in the drive. Drive LED was on in all cases. So it seems there's more to this, than just a missing CPU. Hopefully my ham-fisted use of the Z84C hasn't caused any other issues! Oh, and FWIW, the machine seems to have the 1.4 BIOS and the double-density daughtercard on the mainboard. On Sun, Aug 16, 2015 at 9:29 PM, Eric Smith <spacewar at gmail.com> wrote: