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:

On Sun, Aug 16, 2015 at 8:48 PM, drlegendre . <drlegendre at gmail.com> wrote: Assuming that your Z84C00 is not damaged, I think there's one difference that might make it not work in a circuit that works with the NMOS Z80. The clock input signal of the Z80 CPU, either NMOS or CMOS, is *not* TTL-compatible, but rather has a Vihc min spec of Vcc-0.6V, which for a 5V supply is 4.4V. Back in the day, many Z80 system designers ignored that problem, and drove the Z80 clock input min spec is only 2.4V. In practice, you could usually get away with that in a 2.5 MHz design (original Z80), but at 4 MHz or higher it tended to be noticeably unreliable. The Mostek Z80 databook gives suggested drive circuits; I imagine that the Zilog documentation must have also. Anyhow, even though the Vihc spec is the same for NMOS and CMOS, the NMOS part might better tolerate a clock input that didn't reach as high as the spec. The other thing that could do it is if the circuit might have been designed such that a Z80 with very short clock-to-signal delays wouldn't work. That would be bad design since the Z80 has never had a minimum spec for those delays, so in such a case even a 6 or 8 MHz NMOS part might not work.

Hey Jules, Ah, so your O1 also has the weird screen artifacts prior to hitting 'return'? Weird.. wonder what's up with that? I've only detected activity from drive A (LH side). It definitely does spin, the LED lights up, but I haven't been able to detect any head movement. You mention that the head on yours steps back & forth (indefinitely?) with no disk present - does it behave any differently when the drive door is open vs. closed? In any case, one of us needs to find boot media.. and put some copies in the mail. I have one bootable CP/M machine, a Kaypro 10 - also an Epson QX-10 is here, but iirc it had some issues booting last time I tried it. Might be possible to write media for the Osborne on one of those? (Not bloody likely, but a solution needs to be found). Thanks again for passing this one along to me.. very thoughtful of you! On Mon, Aug 17, 2015 at 3:22 PM, Jules Richardson < jules.richardson99 at gmail.com> wrote:

On 08/17/2015 03:31 PM, drlegendre . wrote: No, sorry! I meant the "boot error" scrolling up the screen (e.g. it's not the result of some kind of stuck key fault or anything). As Mike mentioned, try the shift-quote trick and see if the other drive behaves differently. It's the same whether the door is open or closed. Probably indefinite - I got bored after a couple of minutes of listening to drive heads crunching :-) Aha - I have it now... *somewhere*. I just didn't have any about a year ago when I stopped goofing around with the system that you now have. Unfortunately I don't immediately know where my CP/M disks are; Wordstar and the xdiags disk were in one of the little cubby areas below the drives, so I'm not sure why I didn't leave the CP/M disks there, too. IIRC I got mine from images on Dave Dunfield's site and wrote them on a PC (but you'll need a PC with a controller capable of writing FM density). My todo list is about nine miles long right now, but I can probably rustle you a set of disks eventually if nobody else gets there first! cheers Jules

On Aug 17, 2015, at 3:44 PM, drlegendre . <drlegendre at gmail.com> wrote: Anything that will run ImageDisk or Teledisk will work. It doesn?t necessarily have to be one of those computers, you could pull the 360k drives from one of them and hook them into a ?newer? PC that still has 5.25? 360k floppy support. There?s usually 360k floppy support on motherboards up to the Pentium III era. I personally use an old ABIT KT7A-RAID board which has a controller which is capable of writing single-density/FM disks. I?ve got a half-height 5.25? 360k drive in it connected as drive B and a 3.5? 1.44M as drive A. I?ve used it quite often to create disks from my original TRS-80 Model I which can only do SSSD. I?ve also used it to make disks for the Kaypro and even make disks for my HP-150 which uses single-sided 3.5? disks. -- Follow me on twitter: @FozzTexx Check out my blog: http://insentricity.com

Gents, Do remember that I'm fairly confident this is a DD machine (the described daughterboard and v1.4 ROM are present), so the ability to write +SD+ might not be of concern. It would be nice if the PC could do both, though.. So is there a difference between SD and DD CP/M - Osborne disk images? I mean, other than the obvious storage capacity issue wherein the DD holds roughly 2X the data. If there's such a thing as an "SD" image, can it be written to a DD floppy and still operate correctly? On Mon, Aug 17, 2015 at 6:09 PM, Fred Cisin <cisin at xenosoft.com> wrote:

first track?) of the 'DD' CP/M disk might still be FM, though, even to write out an image. Maybe I'm mixing that up with a different system, though.. I think you might be. I have an Osborne 1a with the DD modification. I can make good Osborne boot disks for it in a 360k floppy drive using Imagedisk on my Pentium II. The latter can't write single density at all though. Tez

On Mon, 17 Aug 2015, drlegendre . wrote: NO. Osborne SD was also single sided. 10 256 byte sectors per track. 100K. "360K" was 9 512 byte sectors, with TWO sides used.

On Tue, 18 Aug 2015, Terry Stewart wrote: I think that the Osborne DD was also single sided. IF I remember correctly (unrefreshed dynamic wetware), it was 5 1024 byte sectors. times 40 tracks, that would, indeed, be 200K. "360K" is mainly just the NAME of a PC format of 9 * 512 * 40 *2 sides The same diskette formatted for other machines could easily be anywhere some inefficient choices, or up to 800K at 96TPI, or even more with various strange choices, such as not having all sectors the same size. Calling that diskette a "360K" provides a relatively unambiguous way to identify the 300 Oersted, 1M unformatted media, and the IBM PC 48tpi double sided floppy drive. Yes, there are plenty of other further possible exceptions to keep some ambiguitiy in the terminology. -- Grumpy Ol' Fred cisin at xenosoft.com

On 08/17/2015 04:09 PM, Fred Cisin wrote: It's odd, but later PC floppy support is often better in the FM support mode. For example, a Socket AM2 board is more likely to support FM than, say, Socket 7 one. ISA SCSI adapters with onboard floppy support are always a rich source of good FDCs--in particular Future Domain, Ultrastor Adaptec and DTC and others All tended to use an NSC DP8473 or a variation of it. That means that you actually have 4-floppy support should you need it, albeit with no BIOS support (which doesn't matter to TD, AD or IMD). I've modified a couple of such controllers to support a third drive on a single 34-conductor cable. For whatever it's worth, --Chuck

On 8/17/2015 12:48 AM, drlegendre . wrote: Do you at least have a logic probe and a 20Mhz analog 'scope? My solution to that kind of issue has been my SD Card HxC floppy simulator, available on eBay or direct from www.lotharek.pl . Info on the design available at http://hxc2001.free.fr/floppy_drive_emulator/ . Then I go looking out on the 'net at bitsavers and other locations for floppy images for whatever system I am working on. JRJ

On Mon, Aug 17, 2015 at 11:40 AM, Sean Caron <scaron at umich.edu> wrote: While that tends to be true for CMOS parts in general, the CMOS Z80 was designed to meet the same I/O specs (voltages and fanount) as the NMOS part. It's possible that the NMOS part has more margin for operation outside the specs, particularly for Vih and Vihc, but is the computer is designed properly that shouldn't matter.

tech manual mentions that the DD upgrade includes a small daughterboard mounted on the mainboard, and the v1.4 ROM, which I assume contains the DD driver code in the BDOS. Both a daughterboard (with a data cable to the floppy drives) and the ROM are present in the machine. By all appearances, it's a late version. The unit was sold the day before Christmas in 1982. Based on their brisk sales at that point, the unit was probably built within a few weeks of the sale date. It also has the final two-piece molded plastic case with dark blue bezel. To answer a couple of earlier questions - yes, I have a logic probe / pulser set and a 20Mhz analog scope. First order of business is to get some known-good media, before I start thinking too much about what might be wrong with it. On Mon, Aug 17, 2015 at 2:23 PM, Mike Loewen <mloewen at cpumagic.scol.pa.us> wrote: