OMNI 4 - a Kaypro 2x Logic Analyzer

A while back I acquired a rare logic-analyzer, whose lone system-diskette needed backing-up.
Now this page is all things OMNI 4

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This KayPro-based "Omni4" logic-analyzer is pretty impressive, for its time... And still certainly usable/useful. 20MS/s on 16+ channels...
30 years old, and it booted up right away, despite having its diskette clamped in its heads for probably decades.
I can't find much on the ol' interwebs about this machine, so it's plausible this is amongst only a few remaining system-disks on the planet!
But copying this aging diskette turned into quite a feat. Many Months of work. Check out the old logs.

Here be other things OMNI 4, as well!


and this project-page has since become about many things OMNI 4.

Check out the old logs for floppy-disk extraction endeavors.

Newer logs are mostly @ziggurat29's amazing work looking into the boot and character ROMs, and even some explanation of the initial/low-level boot process/hardware!


Based on the limited info I can find on the web...
(see a great article, here).

It would seem I've come across a system which may be one of only a few remaining in existence... or at least one of only a few that anyone's bothered to mention on the ol' interwebs.

And I've only got the one floppy disk containing the software for its unique hardware...

And thus beginneth my endeavor into learning a bunch about floppy-disks, drives, and more.

What I thought was going to be a one-night project with a floppy-disk imaging-utility like ImageDisk turned into several months of work, extracting as many sectors as possible via many different methods, including several scripts and a pretty large program I've written myself. Has turned into my learning about MFM-encoding, CRC-checking, Gap-lengths, and countless other factors of floppy-disks, some eccentricities and limitations of various floppy-disk-controller-chips, and more.


So, what's the world-changing-ness of this project...? Well, as it stands, this little piece of history isn't too-well-documented... and if its lone floppy-disk fails before I can make a copy, the entire system could be lost to "bit-rot," plausibly leading its kind to extinction!

Don't want to see that happen!

And, otherwise, even if it's not so unique, at least it'll still be functional, keeping a chunk of metal from the e-waste bin and, with the right owner, giving this system a few more years of usefulness. 20MS/s is still plenty for many needs!

(Heck, most of it is based on well-documented and easily-sourced chips... it could very-well outlast the majority of systems in use today, 30 years after its birth).

Adobe Portable Document Format - 17.47 MB - 10/16/2022 at 07:58


2020-01-27 - Organized OCRed 150PPI Compressed.pdf

OMNI4 Manual! A sincere Thank You to Dominic for scanning this! My OCR technique leaves much to be desired, unfortunately. If you know of better or want the original-quality scans, feel free to contact me.

Adobe Portable Document Format - 43.69 MB - 01/29/2020 at 06:49



Kaypro Technical Manual, Dec. 1984, 1484-D For all Kaypro models. There's another in these files as well [TODO compare] Thankya @Dr. Cockroach, who also notes: "I see that 2X is double-density and double sided 390K and will also read/write Osbourne disks....if that means anything helpful :-)"

Adobe Portable Document Format - 4.30 MB - 01/25/2020 at 00:42



OMNI4 Boot and Logic Analyzer Software Floppy Image Info. Please Read Omni 4 disk image, FINALLY! Use ImageDisk from: If you use cpmtools with it, specify the 'kpiv' format. And PLEASE contact me if you use this... OMNI4 users/owners seem sparse, to say the least! We should be in-conact! eric waz hung at gmail dot com

plain - 966.00 bytes - 01/22/2020 at 05:18



Floppy drive manual... this drive is *not* from the Omni4, but this manual has extensive data regarding the boolean-logic implemented in drives' circuitry regarding I/O. E.g. /STEP is ignored if /WG is active.

Adobe Portable Document Format - 481.84 kB - 11/15/2017 at 11:37


View all 14 files

  • 100 × blood
  • 1000 × sweat
  • 10 × tears
  • 400 × hours

  • This would be so wrong...

    Eric Hertz12/04/2021 at 21:32 0 comments

    ...but yahknow I love hacking things together that were never meant to work together...

    No! NOT with the Omni4, it's already unique... but another Kaypro, or similar style/era luggable maybe... dual-head!

    dunno what it'd be useful for, and would prb require a custom add-on vidcard with custom supporting software... ok, it's kinda ridiculous.

  • A Manual!

    Eric Hertz01/29/2020 at 07:00 2 comments

    Dominic--who happens to be selling the only other OMNI4 I'm aware of in existence--very kindly scanned and sent me the user manual [possibly the only in existence] for posterity! 

    A copy is in the Files section.

    BTW, Dominic's been quite awesome taking the time to do this and more. If you're intrigued by the OMNI 4, consider purchasing it from him at:

  • More

    Eric Hertz01/25/2020 at 01:02 1 comment

    Very difficult to edit a log full of pictures, they seem to randomly disappear.

    Here's a couple more photos from the seller of the other unit [see last log] who has been very considerate in this venture. Muchas Gracias, Dominic!

    Check out my screenshot [from an old log] and compare to above, 1984, 1987!

    "OmniLogic INC was located at 350 Sunset Blvd. N. ,Renton, WA. 98055"

    Mmmmhmmmm, just miles away from where I acquired it. Maybe mine was in fact a prototype, or pieced together from spare/unsellable parts, or something.

    TODOs: There's some great info in these photos from the manual, put it in a log!

    E.G. some comparison to the OMNI II? Not quite grasping what it's saying, the disks are compatible? Gonna have to dig deeper.

    E.G.2. A listing of the files and their purpose

  • Another Exists!

    Eric Hertz01/23/2020 at 09:25 0 comments

    These photos are of another unit found recently on ebay. [Photos used with permission]

    If you decide to purchase this unit, please keep in touch, and consider joining the 'team' here to contribute!

    This unit differs from mine in at least one notable way; mine doesn't say anywhere on it that it's a Kaypro 2x. @ziggurat29 had to figure this out by looking up Kaypro motherboards!

    [Also, an odd note, apparently when using 'cpmtools', one must select 'kpiv', even though the Kaypro IV is an entirely different beast(?)]

    [TODO: take similar shots of mine for side-by-side.]

    This appears to have the drop-down door type latch floppy drives, whereas mine has the rotating lever-latch.

    A manual!

    "Kaypro 2x" heh, that'd've been handy

    Hmmm, my pods are merely heatshrunk, and their cables merely ribbon cables. [And, crosstalk/interference was an issue]. Seems even more plausible, now, mine might've been a prototype?

    A carrying case!

  • DRAM Refresh....

    Eric Hertz11/07/2017 at 08:28 4 comments

    UPDATE: Whoa Whoa Whoa..... (at the bottom).

    So, the question, earlier, came up regarding how the DRAM gets refreshed, if the /REFRESH pin is N/C (which it appears to be, according to the schematic).

    and dammit if I didn't have a long write-up on the matter, and lost everything after this point. So, I guess I'll get to the point.

    There's really no *need* for the /RFSH signal. At least with typical DRAMs. Basically, a row in the DRAM is refreshed whenever a row is accessed. And for a typical Read/Write operation, the row is accessed first, then the column, then the Read/Write signal is sent. So, the row gets refreshed with every read/write access.

    So, why not treat *every* address placed on the address-bus, accompanied by /MREQ, as a Row AND Col access, as though for a read/write? And... now I'm pretty sure that's what happens.

    And I'm betting the custom chip doesn't contain any specialized logic regarding refresh.


    There's still the issues of BANK and /PROMCS, and how those are related to the DRAM... My guess, again, is that *every* address-access on the Z80's address-bus, accompanied by /MREQ, accesses a memory-location in the DRAM (even, for instance, when the ROM is being read).

    BANK is controlled by a bit on the "system port" register... That, as we understand, chooses whether to do memory-accesses from the ROM or the RAM. So, e.g. during boot, BANK directs it to the ROM, then after boot, its directed to the RAM where the OS is stored, etc. (There's some debate as to whether the "BIOS" in the ROM is accessible to applications once the bank has been switched to RAM... E.G. if there could be, say, routines in the BIOS for displaying characters on the screen, could that be called from a user-application, switching into the ROM for execution, then back into the RAM for the next portion of the user-application? I'm sure there are ways, but they may not be pretty... e.g. storing *pieces* of the same code in both ROM and RAM, at the same locations... I'm sure I can find out with further analysis of Ziggurat's ROM disassembly).

    So, obviously, when BANK is set to ROM, /PROMCS gets activated with /MREQ, but /XENRAM does not. But, then, when the ROM is executing (during boot), the RAM still needs to be refreshed... so its still feeding *every* address-access to the row/col system... Which is fine for /RD, since /XENRAM is disabled and therefore the data in the DRAM is not written to the data-bus...

    But what about Write...? /WR is not gated through the custom chip, it goes *straight* to the DRAM!

    Ah hah!

    Write... Never Happens to the Read ONLY Memory.


    Now this leads me to the question of how the ROM can access RAM, for storing variables, etc.

    In what I've seen of Ziggurat29's disassembly, it seems the stack-pointer is set-up in a high-address, e.g. 0xff00... and it seems most other variables are stored up there, as well...

    So, then, BANK only switches between ROM and RAM in the *lower* addresses, and always accesses RAM in the higher ones... simple enough.

    And, again, by treating the RAM as though it's being accessed even when the ROM is, but gating the RAM's /RD signal (/XENRAM), it still gets refreshed.

    This custom chip is starting to seem quite simple, really... a few gates.

    (As Ziggurat29 pointed out a while-back, the 2x motherboard uses this custom chip, but the earlier motherboards are similar in design but use discrete logic instead... I've been meaning to look at those, but haven't yet. All these ramblings are from the perspective of treating it like a black-box... I guess it's kinda like doing math homework where the answers are in the back of the book... should I go look?)


    Whoa Whoa Whoa!!!

    that /WR signal is *directly* connected to the DRAM chips! And they don't have Chip-Selects! That's fine for ROM... but...

    What the heck happens during an I/O write!?

    ... "/CAS is used as a chip select activating the column decoder and the input and output buffers."

    So, maybe I'm mistaken in...

    Read more »

  • 'round the web...

    Eric Hertz11/06/2017 at 12:24 2 comments

    1) An image-search for '"Omni 4" "Logic Analyzer"' results in many hits from this project-page... pretty cool. OTOH, it's quite strange, saying that many of the images are "4-5 days ago" that were actually several months ago. (is it 4-5 days ago that Google crawled on 'em?)

    2) A resulting-image doesn't show anything related to the OMNI4... so I clicked through to the page to see what Google thought made it relevant... Apparently MAME now comes with the OMNI4 ROM (?!)

    "October, 26th 2017" ... "Changelog" ...

    "What's new in this version:" ... "New clones marked as NOT_WORKING:" ... "- Omni 4 Logic Analyzer [rfka01]"


    A bit more research...

    Added as a 'diff' patch 10-15-2017.downloads/mame/mame-0191/

    Cool! Glad to see it won't get lost to bit-rot. Is this your doing @Ziggurat29?

    ...ah... the ROM's not included with MAME's source-code... so I guess it still has to be downloaded from somewhere.

  • Esot's Analysis of Ziggurat29's Boot Disassembly... -- video initialization

    Eric Hertz11/03/2017 at 07:33 0 comments

    Update 11-6-17-2: Notes on I/O addressing thrown at the bottom.

    Updated 11-6-17: Revision with some new understanding...


    Ziggurat29 has done some amazing work disassembling the OMNI4's Boot-ROM and OS(?!).

    (Note that we've determined the motherboard is a pretty-much stock KayPro 2x, but it has a custom Boot-ROM and Character-ROM, both of which are available in the "Files" section of this project).

    Herein, I'm gonna throw up some notes, as I read-through his work...

    (Note that I currently have Zero experience with Z80 assembly-language, and am pretty slow with assembly-language in general, and am unfamiliar with the unit's registers/peripherals... So, this is a great learning-opportunity. Interestingly, this is the same approach I took in learning about the IBM PC/XT architecture, by looking at the BIOS Assembly-listings and schematics in order to determine how to initialize and make use of its peripherals.)

    You might want to take a look at the KayPro Service Manual, which contains schematics of the KayPro 2x motherboard.


    First interesting note...

    The BootROM appears to launch right into external (to the Z80 chip) register-setup... Apparently not much configuration needs to be done within the Z80 CPU, itself.

    There is a "system port" register at 0x14 consisting of quite-literally a byte's worth of TTL Flip-Flops whose outputs are fed to various peripherals, most-notably the Floppy-Controller, but also the Character-Generator ROM (and more?). Setting up the "system port" register is the second operation, the first being setting up the stack-pointer, and both are accomplished in only a small handful of instructions. Wild.

    UPDATE: The system port (address 0x14), from the schematic:

    D0 - /DRV_A              (Floppy)
    D1 - /DRV_B /HD_CTRL_RST (Floppy)
    D2 - /SIDE_ONE           (Floppy)
    D3 - /PSTROB 
            (Parallel Printer Strobe)
    D4 - /MTR_ON             (Floppy)
            (via inverter)
    D5 - /DDEN               (Floppy)
            (Double-Density Enable)
    D6 - A12CH (Write), [PBUSY (Read)]
            (Selects the character-set)
            (See notes in previous log)
    D7 - BANK                (RAM vs ROM?)

    (Side-Note: Appears that the parallel-printer port is output-only, and reading the written values is not possible... wouldn't take much modification to make it bidir... strap a '244 atop that '373, and some glue...)

    Immediately thereafter, is the version-string "2.01", which gets loaded into RAM. This version-string appears on several screens... E.G. When the unit is turned on, as I recall, it says something like "Omni 4 version 2.01" and also, upon loading CP/M, something like "Omni 4 CP/M version 2.01". (TODO: verify... I thought we had CP/M 2.2..?)

    It's interesting to me that these two things are in the Boot-ROM, as I'd've thought CP/M was loaded from the disk (and therefore its version would be dependent on that which was on the disk... like, e.g. DOS 3.3 vs. DOS 6... Or Windows XP vs. Windows 10).

    (To-Ponder... The RAM is already being filled with data, including the version-string and the stack, at this point... More, surely, to come... But doesn't this system use DRAM? Doesn't it need refreshing? How about column vs. row-addressing? Is that *all* handled via dedicated circuitry?! (UPDATE: Looking at the schematic, it appears U29, a custom chip numbered 81-194, takes care of this. This chip appears to handle only interfacing with the DRAM and generating a few clock-signals, from 4.9KHz to 4MHz. As (Actually, it has a couple other outputs I'm working out). Ziggurat29 has pointed-out, this custom chip is a new thing as of the '84 versions of KayPro systems like the 2x, the prior versions used discrete logic, which I've yet to look into. Interesting that, at the time, designing and manufacturing a custom 40-pin chip is cheaper than just replacing the...

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  • Duds

    Eric Hertz09/25/2017 at 11:26 10 comments

    the serially transferred files are duds.

    Apparently pip decided to translate tabs to spaces.... even in binaries, even in binary mode.

    On that note... cpmtools seems to work with the disk image when using the kpiv format.

    Only one hiccup (besides discovering the tab to space conversion)... a large text file ends with a bunch of 0x1a's... (ascii substitute?) Dunno why, but doubtful they belong there.

  • Chargen

    Eric Hertz09/22/2017 at 05:44 6 comments

    u9 appears to be the character ROM... there's a 2732 24 pin EPROM in the socket. Its contents is in the files section, and ziggurat29 decoded it into ascii art. It appears the Omni4 has a custom character set for drawing logic waveforms.

    Ziggurat noted that the schematic shows pin 2, a12 is driven from somewhere... (where?). Well the 2732 doesn't have an a12, but the 2764 does... and the 2732 is pin-compatible-enough that it could be dropped in a 2764 socket, if said socket is designed with that intent... which this one is. And that explains the larger socket than the chip...

    Ziggurat also noted some code in the bios that seems to support character-set switching (via a12, most likely)...

    So my guess is that this was designed with the intent to support two character sets... a normal one for normal stuff... and switching to the custom one for the logic analyzer.

    Seems logical.

    So some tests run tonight:

    A12 starts low, upon reset, but goes (and stays) high as soon as the boot title screen pops up... even before the disk is read, so before the os is loaded, and long before the logic analyzer software is loaded...

    This seems backwards to me... certainly itit'd be more logical to use the default character set for boot, then switch charsets when loading

    An easy change... for a designer... and another thing leading me to think this guy's a prototype (or they ran out of energy for such a simple change... with the assumption few people would be using a $4000 logic analyzer to play games?). While the change would be simple, it would require modifying both the bios and (and any other related software)... so I can see how a backburner idea like that might've been abandoned...

    So... since a12 isn't used on the 2732, and since the 2732 only contains the custom charset, the machine thinks its accessing the custom charset (immediately upon boot and always thereafter) in the higher address space of a 2764... but it's really wrapping around and accessing the lower address space, which is fit in a 2732. 

    So I guess... if this were something I cared to fix, like if i wanted to play games on this thing, I could load the custom charset in the higher addresses of a 2764 and the regular one in the lower space, as designed... then I'd need a utility to switch to the normal charset every time I wanted to play a game... which would mean not being able to just boot off any floppy.

    Or... I could swap it from the presumed-intended design... have the custom charset in the low space and the normal one in the high space... this'd mean having a utility run before the la software to switch to the low space. Could do that in some sorta script, right?.. completely goofy, but a solution that would allow normal disks to boot with the normal charset.

    Now... what if there are games, etc. That expect their own custom charset..? Or, maybe weirder, what if some programs reset to the default charset when starting... Who knows.

    It definitely looks, though, as if this charset swapping is a thing designed in kaypro 2x's... not limited to the omni 4... but am guessing the choice to set a12 high in the bios is specific to the omni4...

    Anyhow, a curiosity.


    Probing: A12CH appears to be connected to U58, PIN 16... heading back to the schematic... yep... there it is, sheet D just as it says... dunno how I missed it before.


    Replaced the second 5.25in drive with another 3.5... MUCH easier, now, to try out other software... (looking into something that'll transfer the disk contents faster and reliably for viewing on a newer computer).

    Not sure where I stand with this thing... I'm starting to get hackish ideas... that can't end well... and... could be done with a normal kaypro, anyhow...

    (Seriously: installing a soundblaster has crossed my mind a couple times... maybe I'd better get this thing out of my sight ASAP... I can do stuff like that with #Improbable AVR -> 8088 substitution for PC/XT instead of frankensteining one of the last of an endangered...

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  • Serial Transfer

    Eric Hertz09/18/2017 at 00:26 19 comments

    Oddities abounded... apparently the KayPro 2x doesn't have a standard serial port pinout.

    Key factors include: Only using CTS, and Tx and Rx swapped. I found  this pinout in the technical reference manual.

    Here's a cable I hacked from a typical null-modem for communicating with a newer PC...

    DB25 (M)       DB9 (F)
    2  RxD         3 TxD
    3  TxD         2 RxD
    7  GND         5 GND
    20 CTS         4 DTR
                   1 DCD,6 DSR (unnecessary?)

     Note that the end-result is very different than a null-modem... weird world.

    (CTS <- DTR, NOT CTS <- RTS, was necessary, otherwise the transfer never starts)

    Truns out pip doesn't convert *to* ihex, only *from*... well that doesn't help. OTOH, looks like the serial port does infact send 8 bits.

    On the PC-side I used 'dd bs=1 if=/dev/ttyUSB0 of=<filename>' (after setting the baud-rate to 300bps (!!!))

    On the KayPro side I used 'pip tty:=<file>[o]'

    tty: is the serial printer port, and [o] indicates to send the file as binary, so it won't stop early when a byte matching 'end-of-file' is found.

    After the transfer completes, the KayPro returns to 'A>'... at which point I type <CTRL>-C on the PC.

    The process is *slow*... and pip doesn't say much while it's running... or not (e.g. when the handhaking is not correct, it just stalls... forever?) 

    So I opened another terminal window on the PC and ran 'ls -l <filename>' repeatedly to make sure that filesize was increasing. 

    Many files from the disk are now available in the files section, after literally hours of file-transfers ;)


    There were some strangenesses during the transfers. I transferred K2X* twice, and verified they matched. LA.COM I transferred numerous times and verified they matched, but the remaining I did not verify. Oddly, unlike the others, their file-sizes didn't match the output of 'D.COM' (which is essentially 'dir' or 'ls'). One I tried twice, both times receiving 4K, when D.COM claimed it was 6K... so I dunno.

View all 42 project logs

Enjoy this project?



Ken Yap wrote 01/22/2020 at 05:32 point

I used to have a DOS program that could read many flavours of CP/M diskettes including the Kaypro luggable by programming the 965 appropriately. That was almost 30 years ago I think. Might still be in some DOS shareware archive. Edit: I think it's 22disk.

As for the refresh, does this machine use a Z80? You know that it implements hidden refresh right?

  Are you sure? yes | no

Eric Hertz wrote 01/22/2020 at 05:44 point

believe me, I tried every disk imaging utility I could find, and several different drives. Hundreds of sectors were unreadable, feel free to look through the old logs to see how it went, it's explained in great detail.

Nope, didn't know about Z80. Interesting.

  Are you sure? yes | no

Ken Yap wrote 01/22/2020 at 05:49 point

Ah the floppy is probably unusable then.

  Are you sure? yes | no

ziggurat29 wrote 09/06/2017 at 21:46 point

minor point since I was just re-reading your logs (to download some of the blurry board pics for comparison):  'denatured alcohol':  it's alcohol that has toxic stuff added, so you can't drink it.  (Otherwise it is ethanol, which you could drink, but then there'd be tax and whatnot on it).  The stuff they add is wide and varied.  We used it as kids for the alcohol lamp in our chemistry set.  You can probably use it just fine as a solvent, too.  But 'maybe', because as I said, the particular denaturant used is vendor-specific.  Usually it's methyl alcohol, though, so you'd be fine with that.

  Are you sure? yes | no

Eric Hertz wrote 09/07/2017 at 05:15 point

Stupid phone deleting responses.

Thanks! Methyl is the claim on the label. I'm no chemist, so your word is helpful.

Photos... I'll definitely be taking better photos and documenting the major chips... may be a bit since it's assembled finally...

Something specific?

  Are you sure? yes | no

ziggurat29 wrote 09/07/2017 at 14:38 point

Truly, I was trying to get a better handle on the unit's specifics in advance of attempting to disassemble the software on your disk image you so meticulously restored.

I am currently guessing this is a 'Kaypro IV'.  Kaypro's numbering was confusing; there was a '2' and a 'II' and a '4' and a 'IV', which were quite different.  E.g. the 'IV' ran a 2.5 MHz, and the '4' (release less than a year later) ran at 4 MHz.  The 'IV' and '4' had significantly different electronics designs (as I understand), but the 'IV' and the 'II' were electronically similar, apparently differing in the upgrade of the DSDD drive.
I did find a schematic to the 'II', but not the 'IV', so I'm hoping those similarities hold true.  I also found a manual for the CP/M for that unit, but not for the various 'Perfect Suite' apps that shipped with it.  And of course not the Omni4 manual (do you have that?).  (I can send you all these docs, of course, if you want them.)
Anyway, don't go out of your was to take it apart again, but it would be useful to verify some assumptions at some point, so let me know if you have plans to re-open and I can send you some more pointed questions (or I'll just formulate some anyway and send those to you for future).
Lastly, it seems there is coincidentally a guy in Oregon (I think) who also recently found one of these units, albeit the prior model (Omni2?), who alas does not have floppies or manuals.  What a weird coincidence!

  Are you sure? yes | no

Eric Hertz wrote 09/08/2017 at 00:44 point

Mr. Gung-Ho!

Alright, I'll throw more energy in trying to document this thing... I have to open it up for the latest floppy-endeavor, anyhow.

I *think* It's a Kaypro 2x (?) But I'll get on figuring that out as well.

No manuals, but the help file is full of info (except, now I recall there's a section that says "to be completed" or something... more in favor of its being a prototype?)

Ah, right... it's *difficult* to read these files without knowing the model-number/OS since they all use different methods of storing the files... I gave up at that point, managed to get a directory-listing via a linux-box I think, but not sure I ever came up with the right combination of 'mount' settings to access all the files...

Interesting about the Omni2, link?

  Are you sure? yes | no

ziggurat29 wrote 09/08/2017 at 02:07 point

Oh yes, I'm quite serious when it comes to disassembly.  It's a bizarre fetish of mine -- I don't know why, but I find it very relaxing.  Maybe it's the same thing that impels some folks to fiddle with watch mechanism.

Anyway, this is your project of course, so any looking you do is purely a bonus for me and don't derail your other plans my account.  I currently have some trouble with the disk image you placed in the 'files' section.  It's probably something I am not doing correctly in reading it -- I can read the directory, but I cannot reconstruct the files.  I sent a more detailed explanation via PM (figuring most folks would prefer my not polluting your discussion area with longer messages).

Upon revisiting the Omni2 inquiry stumbled across yesterday, I now see my memory failed me and that it was not so recent: 2013.  (But in the 34 years since the unit was current, what's 4 years?)


  Are you sure? yes | no

ziggurat29 wrote 08/31/2017 at 23:12 point

Could your PCB mess you were dissolving with alcohol be a conformal coating?  It was popular in the day.
Pity the board picture in your mar 30 post was blurry (I know, I have the same trouble with phone cams), but I'm assuming its a Z80 board.

  Are you sure? yes | no

Eric Hertz wrote 09/01/2017 at 05:03 point

thanks for reminding me of that post... lotsa comments there regarding what that coating may be and how to go about solving the mess... not sure where I got the idea it's lacquer. Funny thing it's only on the logic analyzer board but not the motherboard.  The logic analyzer board doesn't have a processor... just a couple DMA controllers, as I recall. The motherboard is z80.

  Are you sure? yes | no

ziggurat29 wrote 09/01/2017 at 14:07 point

It seemed unusual to me that unusual that it would be used at all, but I suspected that it was just a common practice with the assembly house they used. Now that you mention it is only on one board, I'm not so sure.

Conformal coatings were typically used to control things like dielectric and to avoid ambient humidity being absorbed into dust and changing resistances (in very high impedance circuits).  It was particularly used on analog boards.  Maybe they were being defensive on the IO board design.

Anyway, if it is conformal coating, you probably can scrub away with impunity and a toothbrush, but I certainly leave that decision to you -- you don't want to break your toy!

Also, I myself have a bit of a fetish for disassembly (and in particular Z80 since that is what I cut my teeth on).  If there are any boot roms, or programs on that disk that you would like disassembled and commented, let me know.

  Are you sure? yes | no

Eric Hertz wrote 09/02/2017 at 05:22 point

wow oh wow! Disassembly of something like this could be quite something! I have no idea what I'd use it for, off hand, but that could be quite handy. If I understand properly, it uses a typical k2x bootrom, if so the application is the special part. 

Was half-tempted to bring it outta storage for something to fix up... and allegedly it only takes 65W, so could run off my inverter. Now the temptation is stronger ;)

Got me thinking... if the powder from the coating isn't a problem for functionality, it's probably best left alone, should anyone ever be interested in tracing out the circuitry... rather than risk ruining any markings on chips... then if the coating itself is blocking a marking it could be spot-cleaned... ugly, but maybe better than risking further damage.

And you probably got it... the board house probably did it... the other boards seem to be standard kaypro stuff... and otherwise the omni4 stuff is just a sheet of aluminum and a custom painted case... of course the omni4 crew wouldn't make *everything*, now that you mention it.

Kden... it's settled, I'll take the blasted thing on the road!

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ziggurat29 wrote 09/06/2017 at 15:09 point

OK, well I see you did post the floppy image.  I'm not sure what format that is in, but I'll study it.  I /should/ be able to reconstruct the files from it, sector-by-sector, if I can gain an understanding of the CP/M file system (which I'm sure is documented somewhere).

Anyway, if I can do that, then I'll try some disassembly.  I'll certainly have to ask you about electrical stuff along the way, since I don't have the physical box to study.  Hmm, I should probably search for a Kaypro schematic -- that might exist somewhere, and would save some trouble in figuring out the standard stuff.

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Greg Kennedy wrote 03/29/2017 at 15:44 point

Well done!

So... when are you building the Floppy Disk Emulator, to store the image on flash and serve it entirely solid-state to the machine?

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Eric Hertz wrote 03/29/2017 at 23:59 point

You know I thought about it... They do already exist, though... ;)

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Dr. Cockroach wrote 03/29/2017 at 08:34 point

Oh boy, Blood, Sweat and Tears. You should win something from the contest for all that effort if it was up to me :-) There must be

many older systems out there that need that kind of love and attention to keep them going, Great Job :-D

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Eric Hertz wrote 03/29/2017 at 08:58 point

hahahahaha... I dunno if I've got that in me... I like the concept, it kept me going... I even thought maybe my unknown-calling was as an archaeologist. But boy was I ready for that much-needed sense of completion! but... "I wonder if..."  ;)

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Dr. Cockroach wrote 03/21/2017 at 19:45 point

Hey there eric, Man you have put in a lot of work on finding those sectors, I know that I could not have stuck with it as you have :-)

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AVR wrote 03/03/2017 at 12:35 point

what a sick find dude!

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Eric Hertz wrote 03/03/2017 at 20:18 point


It was given to me many years ago from an old boss who I think had it for many years prior without probably ever having used it. I just turned it on for the first time a few weeks ago, having figured the floppy-disk would've been long-ago corrupted to the point of unusability. Turns out the darned-thing booted right up into the program without a hitch! 

The only hitch was when I tried to make a backup of that floppy... which I've been doing for the past three weeks(!)

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Dr. Cockroach wrote 03/03/2017 at 12:00 point

Man oh man, that brings a few flash backs to me. I had a KayPro II quite a few years ago and the disk system never stopped working. But yea, better get a backup made asap :-)

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Eric Hertz wrote 03/03/2017 at 20:28 point

This is my first KayPro and/or CP/M endeavor... But the machine is surprisingly robust. And, surprisingly, given its age, still useful.

It's reassuring that you had a good experience with the disk-system. I've been a bit hesitant to believe floppy-disks/drives can be in any way reliable, and have been proven wrong on several occasions with this system. (Seriously, the heads were clamped on the disk while the thing had been lugged-around and stored for decades, and it booted right up!)

If it weren't for the fact this appears to be a one-of-a-kind floppy (can't find any images, or even mention of *users* on the interwebs), I'd be tempted to just use it until/if it wore out. But, yeah, probably shouldn't do that when it seems to be the only one in existence.

I think you're right, this appears to be a relabeled/modified KayPro II.

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Dr. Cockroach wrote 03/03/2017 at 21:17 point

Hello again, Just my three cents but I would just keep it the way you got it. I know how it is with the cord for the keyboard, the Kaypro II was the same just not CP/M. If you ever tire of it I sure would not mind providing it a good home ;-)

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Eric Hertz wrote 03/03/2017 at 22:31 point

Awesome! I'll definitely keep you in mind. And I've no doubt you'd give it a much-better home/purpose than I. I'll likely be getting back to #sdramThingZero - 133MS/s 32-bit Logic Analyzer sooner or later... once that thing's functional, I'd probably just be putting this guy back into storage. Though the thought of having a logic analyzer to work on my new logic analyzer is slightly appealing, if you can wait for a while :)

Glad you spoke-up about the keyboard. It's an annoyance, but I can imagine a modification like I'd attempt could de-value a vintage.


Hah, I just remembered I have *another* logic-analyzer (peripheral) which I tried to back-up its floppy-disk a while back with errors, as well. I'll look into that one next, maybe this guy'll be available sooner than later.

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Dr. Cockroach wrote 03/03/2017 at 22:54 point

Hey, that's cool beans Eric :-) Take your time but I do like the older systems. Kinda why I am building IO Lol 

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