Posts by jlopez

    Thank you, gpospi .

    Yes, I remembered yesterday that you got it in a single card. Looks cool. I think you may be able to help me a little, we'll talk later in another thread.

    This night I also found that I was wrong about the memory cards being the same as in the P2. There is a slight difference I have realized this morning that allowed a major redesign in the computer.

    Today I will run its first test.


    On Friday I received this nice thing, courtesy of rfka01 .

    It was somewhat tricky to acces the inside parts but I managed to enter without breaking anything.

    Not much different from a P2 system.

    About those two...

    I'm a bit disappointed. I expected TA to build a 64K board and not having the same 48K+16K structure.

    This one took me for surprise. At first I thought that an EPROM was missing, but seems that the P3 has 4K ROM, isn't it?

    After a first check ( rfka01 told me that the unit is non-functional) I found an issue at the floppy controller board.

    That blue capacitor (C21) located near the FD1791B was dead and if I had turned the computer on I would have had a short circuit in the 12V line. I've also checked all four fuses and found no more failures. I replaced the capacitor about three hours ago. I'll clean and test it during this week.

    The keyboard... yeah... so heavy that it could be used as a melee weapon. It seems that was made to last long (and also for IT to kill their bosses too).

    But I am quite convinced that not everyone is posting his/her newest acquisitions.

    I imagine so... like when I got a 3032 with East german U256 memories...

    But for the large amount of material per person I guess:

    A) in Germany you have really high salaries


    B) the speculative bubble is still low there

    Here, this kind of stuff is starting to get prohibitive. And when referring to new publications (I'm not talking exclusively of videogames) we are subject to real discrimination when comparing with the other European regions.

    I am clueless...

    This thread is always full of new acquisitions (usually coming in generous numbers each time). And I was unable to find things other than overpriced trash the last time I went to the flea market. Seriously, I may be in the worst region of western Europe... I cannot find a better explanation to this phenomenon.

    By the way, nice captures!


    In the Spanish forums where I use to post another user posted about an adapter which allows the Panasonic KX-R194 to be used as a printer. Knowing that there, in Spain it may have no satisfactory answer I offered myself to ask here, as I know there's expertise not only in computers but also in typewriters and other good old electromechanical devices.

    Wouldn't anybody know about the foresaid module, with reference "KX-R60"? Is any document out there to check how it works?

    Thank you very much!


    There's an explanation to that. I know this model (I nearly had one, but escaped) and I have a 8032 + 64KB upgrade. As you said the model was cost reduced, in part because both boards were fused. There's no intermediate between 4116 and the 4164. If they wanted to make it with just the desired memory size, then the RAM IC count would have been 8 x 4164 and 16 x 4116 for a total of 24 ICs. Then, there are also the support logic in order to make it work, both banked and unbanked. You may expect a pretty high number of components just for memory and bank control. A second reason may be the control register. While there's an unused bit that could have been used to switch it, there is no free one to write-protect it. Changing this register format would have made this model compatibility with the 8096, which was the goal.


    I've updated the harting with Vcc and GND signals. The data bus has been declared this time as bi-directional (it was previously defined as output-only).

    I've reverse-engineered an important part of the 74's, although there's still a lot of work to do. Like in a subway, I've named the studied chunks as colors.











    I've named the ICs U1-U15. The vias found connected to the chunks have been named V1-V6. Parts of J3 have been defined. In labels, when the connection name contains "#" it is usually followed by a signal name or a pin number. If it is only a number, it is a reference to a pin, otherwise it is the signal name.


    Thank you again for the pictures. The first one will be very helpful. Unfortunately, when defining the connections from J3 to the main board I am of no help. I guess you need someone with better understanding of this computer than me for that part.




    The only reason for the 472 to exist was to deceive. Somewhere during early 80s a tax was introduced which affected computers with a RAM size <= 64KB. Amstrad took their 464 and removed the ROM, placing a socket where a daughterboard was connected. That little board contained the ROM and a 8KB SRAM (I think it was) and only the ROM was connected. If I recall correctly, it wasn't even connected to Vcc, so they were useless. In the manual they stated that the extra 8K memory was "not accessible to the processor because it was used by the ROM to excute the new functions". Yes, a ridicule excuse. That being said, when the tax was retired the 472 died with it and the 464 returned to the Spanish market (officially).




    Thank you for the new pictures. They have been useful. All ICs have been successfully identified now.

    I started to draw a proper schematic wiht KiCad, but the only thing "displayable" is the pinout of the Harting-64. At this point, it is still incomplete but at least it's cleaner.

    In my opinion, the contacts C (16, 18, 20, 22, 24, 26, 28, 30) may be the addresses A5-A12, but I won't be able to check it (continuity tests are required, as some tracks are under the ICs on the component side or under that blue socket on the solder side).

    I've signalled some labels and calculated the resistors' values. Those orange components seem resistor packs in a star configuration, but as I cannot see their reference it is just a guess.

    I've drawn the gates on the solder side to make it easier to draw the schematics. I hope that after flipping and flipping them I haven't drawn them wrong. The 74LS641 are bus transceivers. The bottom one seems wired to work as some kind of shift element.



    I've tracked a few tracks and identified some connections on the Harting.

    I still haven't checked connections within the 74's or the 2114s. ICs marked with an asterisk aren't confirmed (shadows, flash or not enough resolution for a successful identification). Some tracks from the top side are marked. Some Vcc and GND tracks are also identified, but this is not reflected on the image. Near the Harting there's a mark: "crt".



    Yesterday night, after some search I found only the documents for the original 6845-based AIM video card, but not this one in particular. Have you found them?

    I would like to ask you if I could reuse your pictures to get an idea of how this board behaves.


    I have the original docs for the AIM. While I'm not willing to sell them (because then I'd have mine without docs) if you need any of them I could provide scans.

    You've got a nice piece here, I'll follow closely as my unit came with no extensions and learning about them is important to me. Note that is strange that is wasn't upgraded using the bus expansion slot, but the CPU socket. Just like PETs were meant to be upgraded.

    Good luck!


    Thank you for answering!

    The fate for most computers of that era is already sealed. With custom chipsets they will not last long. Other systems will last for a very long time, such as the Commodore PET (pre-CRTC), Apple II or the ZX-80, which are made of generic, off-the-shelf materials which, in case of the most specific ICs can be replaced with small mods. However, we have a case of a computer which has avoided its demise by getting rid of its ASIC. The ZX Spectrum case should be studied. They replaced the ageing ULA with (mostly) 74 series ICs. This means that, as long as the 74 series (with TTL levels), the Z80, its ROM and its RAM are made, Spectrums will be able to be made and repaired (although those with original board will eventually fail nevertheless).

    I think if the Harlequin philosophy could be applied to this system, we would be able to keep them running for some more time (and also to introduce new units). The truth is that I'm not a fan of FPGA or CPLD. They obscure hardware implementation and make it less repairable in case of failure. Also, they doesn't feel retro enough. ;)



    gpospi , I know you have tried the working cpu in the failing board (with no result), but have you tried the "faulty" 8085 in your original board? If it works, then the suspect would be some other component rather than the CPU, such as the oscillator.

    Ich bin wieder vorsichtig optimistisch: Habe mir das CPU Board angesehen, das gestern im Zuge der Kondensator-Explosion auf dem Video Board beschädigt wurde (und seither die Kurzschluß-Notabschaltung des Netzteils auslöst). Der Schaden dürfte sich zum Glück in Grenzen halten. Das Board selbst scheint komplett ok zu sein, alle Leiterbahnen und Kondensatoren sind ok. Allerdings hat sich offenbar die CPU verabschiedet und verursacht nun einen Kurzschluss 5 Volt / Masse. Bei entfernter CPU läuft das Netzteil problemlos an.

    Ich hab mir also eine Ersatz-CPU bestellt, sobald diese eintrifft werde ich die Tests wieder aufnehmen. Mein Plan ist, dieses CPU Board dann testweise in meine P2 einzubauen. Vielleicht sind mit diesem Board (ohne Modifikation für externen Takt) und den darauf befindlichen ROMs dann die Floppy-Probleme endlich beseitigt. Viele weitere Möglichkeiten sehe ich eigentlich nicht mehr...

    You already have another 8085 8)

    So ich habe mal wieder ein Update, die Zusammenfassung lautet "viel erlebt, aber wenig erreicht". Im Detail:

    • Die Teile von Robert ( rfka01 ) wurden heute geliefert. Am Wochenende hatte ich mir schon ein altes PC Netzteil für einen Versuchsaufbau vorbereitet, sicherheitshalber hängt auch eine Festplatte daran um etwas Last zu erzeugen.
    • Im ersten Schritt habe ich die Karten auf Kurzschlüsse in der Stromversorgung überprüft, konnte aber zum Glück keine Probleme feststellen.
    • Voller Erwartung habe ich nun also PC Netzteil, Backplane, CPU Karte, Display Karte und Tastatur Interface zusammen gesteckt. Das sollte ja für einen System-Start bis zur MOS Einschaltmeldung reichen. Beim Einschalten der Stromversorgung beginnt die Reset-LED auf der Tastatur ordnungsgemäß zu leuchten, die Freude ist groß.
    • Leider kommt kein Bild am Monitor und nach einigen Sekunden verabschiedet sich das Display-Board mit Knall und Feuer. Also entferne ich die Display Karte und überprüfe den Schaden. Hier ist ein Kondensator explodiert, der sollte leicht zu ersetzen sein. Offenbar wurde aber auch die CPU Karte in Mitleidenschaft gezogen, jedenfalls verursacht diese nun einen Kurzschluss. Mit diesem Versuchsaufbau komme ich also nicht weiter.
    • Somit baue ich nun die "neue alte Floppy" in meine vorhandene P2 ein um zu sehen, ob damit nun die seltsamen Lese- und Formatierungsfehler verschwinden. Das passiert leider nicht, es treten alle bekannten Fehler unverändert auf.
    • Damit fällt mein Verdacht nun endgültig auf den Floppy-Controller meiner Maschine. Also baue ich den Ersatz-Controller ein und hoffe auf Verbesserung. Leider wird auch diese Hoffnung enttäuscht, die Maschine verhält sich unverändert (Booten von Floppy A geht problemlos, Formatieren mit FOKO scheitert, Zugriffe auf Floppy B erzeugen BDOS Fehler). Auch mit anderen Floppy-Kabeln ändert sich nichts.
    • Ich habe leider kein Oszi um die Signale genauer zu untersuchen. Insofern werde ich mich wohl geschlagen geben und die P2 eben mit einem Laufwerk verwenden. Letztendlich boote ich die Maschine ohnehin nur "zum Spaß" ins CP/M oder BASIC, konkrete "Aufgaben" erledige ich damit ja nicht.

    Other than the blown cap, is there any damage at the video display board?

    "Snipers"... more like "U-boots".

    Silent, invisible. They are hit but don't know from where. It's aggressive but effective, the perfect way to end a bid war. And yes, competitors have no chance, unless they have an automatic bid larger than you, but their victory becomes a pyrric one.

    Once, we found a very rich material source in UK. Someone was selling the content of an entire garage full of Commodore, Sinclair, Amstrad, and other computers, spare parts, printers, floppy units, etc. I got an important part of it at low price with this tactic. Like VIC-1515 for 5€ or a CBM-3032 case and monitor for 20€. We managed to get a Victor-9000 complete with original box too. Our good old days of terror bidding... 8)

    An improvement I did: syncing music with the timer's end, especially a tense one with its climax just at the end. I chose (the very convenient) "Konvoi", by Klaus Doldinger. Having a music piece of this kind helps not to miss the perfect bidding time.


    I have a first version of the design, using common parts and adapted to the 96-pin bus of the P2. At first glance it can be seen that an entire byte of the address is unused, so in case of a wirewrap the area near the connector wouldn't be as crowded as the memory card was.

    The analog part is still to be drawn, I have never worked with DACs or OPAMPs. I think I'll use DAC0800 but I don't know about the replacement for the LM307... I'm going to do some good research to find suitable present-day replacement.

    This is enough to add some ICs to my BOM list.

    Thank you very much,


    So , in that case sorry about my doubts.


    Why did you thought I was joking? ::cry::

    After I found the schematics I made some research and found other computers (mainly Russian clones of other systems) implementing sound using the same approach. Why Russian clones can have some good audio and my poor old P2 just a beeper? That's not fair!

    Don't worry, after all it's a hobby and everything here is just for fun and for learning purposes. :)

    Yesterday I got a very good deal for 25€.

    The machine is in very good shape, seems like it hadn't been used. This leaves me with only 5 models in the Nintendo portable consoles series (not G&W) to acquire (GB Light, GBA AGS-101, 3DS, new 2DS, new 3DS).

    This Monday I'll travel to Barcelona. I'll take this oportunity to acquire new components (do you believe it? I have a lot of 32K SRAM, but no 128K ones! ). As I don't know how much time wil pass until I could travel again and acquire more components, I'll try to get enough material to cover as many projects expected to take place during Summer.

    So I think it's time to present an idea I've been coving since January, when I (accidentally) found a MC-16 schematics scan. The MC-16 was the first sound card the Apple ][ had, and (I may be wrong) it was maybe the first commercial sound card a microcomputer had.

    Examining the diagrams I learnt some things. First, that a simple soundcard contains two sections: an analog one containing an operational amplifier, DACs to control the volume of each voice and resistors to mix the different voices; and a logic one which is a programmable signal generator. In the case of the MC the signal generator is a 8253 PIT, which was made as a support chip for the 8085. The original PIT is not made anymore, but the 82c54 is still in production and they are compatible.

    About the name of this project:

    I decided to name it "Shakuhachi". A shakuhachi is a very simple vertical flute made of bamboo.

    Image courtesy of Wikimedia commons.

    Just that, a bamboo pole with some holes. And the MC is just a counter with some DACs... Do you see the simile? :)

    This project is sure that won't be finished during Summer (so no false expectations). But the goals are the following:

    #1: Clone the design, adapted to use modern-day components

    #2: Experiment the following designs:


    Square wave




    Sawtooth/Inverted sawtooth


    #3: If (#2) successful, think about integrating as much as possible in a card.

    Thank you for your time and my apologies for such ugly and dirty drawings.

    Interesting idea to create a board which may replace several other potential faulty components. Unfortunately I am not so deep into hardware design and the memory layout of the P2. Overall I am not sure if having e.g. the floppy ROM "backup" on the board is very useful. If the floppy controller is broken, just having a working ROM will not really help. If the floppy controller is generally working, I would replace a potentially faulty ROM directly on the controller.

    Hello gpospi ! Nice to see you too.

    Well, this part would only replace the rom containing the controller routines. If the floppy controller is failing unfortunately another solution should be sought (aka. another board). This is meant to solve memory issues, both random and read-only. Unless you floppy controller ROM is failing it won't help to solve your floppy issues. Unfortunately, this is outside the scope of this project, but sure I'll take a look and taking notes and ideas for possible future projects.

    I'm sorry about delaying this so much. My inexperience weights a lot...

    Hello Helmut, nice to see you!

    This summer will be full of computers. I've a Commodore computer coming and maybe a third P2 :S.

    My philosophy about the board is a restorative one, it is not meant as an upgrade (well, for 48K P2 sure, it will be an upgrade). Video memory is not addressed in this project.

    ROM is switched on/off with a switch because is meant to coexist with the original ones. In case of an original ROM failure, the only thing to do to restore the computer to a functional state would be activating the appropiate switch. This way the TMS ROMs are left out of the equation the same way as the 4116 would. Also, if they were not deactivated, conflict between the original ROMs and the new one may arise.

    Thank you very much,


    YaY : Dtoday finally my little 9 "Bernsteiner arrived - was a snapper - originally this comes from a typewriter, see manuals, which I like to give here:)

    This monitor is familiar to me. Was this Canon device powered with a Z80 derivative and designed to use 3" floppies?


    I've returned, and with a new version of the schematics! :)

    Those modifications should enable/disable RAM sections as well ROM using a switch.

    Switch positions are:

    ROM Switch (SW1 on the schematics):

    SW1 SW2 SW3 Effect
    0 x x MOS ROM (on the new board) disabled
    1 x x MOS ROM (on the new board) enabled
    x 0 x Floppy control ROM (on the new board) disabled
    x 1 x Floppy control ROM (on the new board) enabled
    x x 0 Video and keyboard control ROM (on the new board) disabled
    x x 1 Video and keyboard control ROM (on the new board) enabled

    RAM Switch (SW2 on the schematics):

    SW1 SW2 SW3 Effect
    0 x x RAM 1800h-2000h disabled
    1 x x RAM 1800h-2000h enabled
    x 0 x Memory limited to 8000h-FFFFh, bank switching disabled (aka 32K mode)
    x 1 0 Memory map expanded to use the 8000h-FFFFh range, bank switching disabled (aka 48K mode)
    x 1 1 Memory map expanded to use the 8000h-FFFFh range, bank switching enabled (aka 64K mode)

    Have a nice evening.

    Ja Danke, das hatte ich nicht bedacht. Bei allen anderen CP/M Computern in meiner Sammlung habe ich 64 KB RAM ab 0000h, diese haben ja kein MOS Betriebssystem "davor". Irgendwo sollte ich vom Tiny Basic den Source Code haben, vielleicht versuche ich damit mal auf der P2 mein Glück. Aber zuvor werde ich dem Diskettenlauferksproblem nachgehen. Zudem werde ich mit den MOS Routinen "F" und "C" den Speicher näher untersuchen.

    For the source code of Tiny Basic, you may check Github.