3 ms·

do you know more home computers that did the display controller like the apple II did? I think it may be inspiring to people who make their own diy cpus

jandrese 2y ago
I think the Commodore PET used discrete TTL as well. This is first generation stuff for home computers, the costs are so high that manufacturers were highly incentivized to make graphics chips as soon as the technology was viable, right around 1979 or 1980. Anything made from then on is going to have a dedicated graphics chip of some kind just for the cost savings.
- PaulHoule 2y ago
  So did the other member of the "trinity", the TRS-80 model I. My mental picture is that the kind of display controller I'd like to build is about two large breadboards stuffed with 54xx chips. Such a thing is a bit simpler than a minimal CPU but not that much simpler because you need the stuff to interface with memory. I'd probably want to buy an oscilloscope and/or logic analyzer but maybe I could run it slow and use an AVR-8 Arduino to run test sequences. Almost everybody who builds throwback computers today uses either an FPGA or a microcontroller for the display controller. For instance https://github.com/fdivitto/FabGL https://github.com/fdivitto/FabGL is a highly flexible controller implemented for the ESP32 which can do tile-based graphics and sprites for games but also emulate an ANSI terminal. This is used in this SBC https://www.olimex.com/Products/Retro-Computers/AgonLight2/open-source-hardware https://www.olimex.com/Products/Retro-Computers/AgonLight2/o... which I am going to highly recommend because this machine is compatible with the old Z80 machines but has a real 24 bit mode with 24 bit registers and also performs an order of magnitude better than any Z80 machine did back in the day. Modern systems usually avoid the unified memory model that was popular back in the day but that also usually held back the performance of the CPU because one way or another the VDC was stealing cycles. The AgonLight board communicates with the display controller through a serial port, for instance. This thing http://www.commanderx16.com/ http://www.commanderx16.com/ has a memory mapped register for the address in video RAM the CPU wants to read/write and another for the data. The address register will auto-increment when access the data register so you can read or write video RAM at high speed just by repeatedly accessing the data register. The CX-16 uses an FPGA as a display controller https://github.com/X16Community/x16-docs/blob/master/X16%20Reference%20-%2009%20-%20VERA%20Programmer's%20Reference.md#chapter-9-vera-programmers-reference https://github.com/X16Community/x16-docs/blob/master/X16%20R...
  - kjs3 2y ago
    two large breadboards stuffed with 54xx chips There's no need for mil-spec chips for this. Waste of money.
  - beepill 2y ago
    > " I'd probably want to buy an oscilloscope and/or logic analyzer but maybe I could run it slow and use an AVR-8 Arduino to run test sequences." that's literally what i want to do because Im too broke for either lol you can squeeze an arduino's adc utilizing its timers and interrupts instead of using analogRead() in a loop: https://www.instructables.com/Girino-Fast-Arduino-Oscilloscope/ https://www.instructables.com/Girino-Fast-Arduino-Oscillosco... https://digibird1.wordpress.com/arduino-as-a-5m-sample-osciloscope/ https://digibird1.wordpress.com/arduino-as-a-5m-sample-oscil...
- basementcat 2y ago
  PET used a clone of the Motorola 6845 (also found in MDA and CGA adapters for the IBM PC). https://en.m.wikipedia.org/wiki/Motorola_6845 https://en.m.wikipedia.org/wiki/Motorola_6845 https://retrocomputing.stackexchange.com/questions/7117/how-did-the-commodore-pet-80-column-display-work https://retrocomputing.stackexchange.com/questions/7117/how-...
  - PaulHoule 2y ago
    See also https://en.m.wikipedia.org/wiki/List_of_home_computers_by_video_hardware https://en.m.wikipedia.org/wiki/List_of_home_computers_by_vi... Note Don Lancaster's technique used for video in some computers https://www.tinaja.com/ebooks/cvcb1.pdf https://www.tinaja.com/ebooks/cvcb1.pdf such as https://en.wikipedia.org/wiki/ZX80 https://en.wikipedia.org/wiki/ZX80 In some strange sense this is like using a microcontroller to implement a CRTC except you're using the main CPU to do the work.
  - jecel 2y ago
    The first couple of models used TTLs for the video circuit. These were replaced with the 6845 later on.
detourdog 2y ago
I lot of the Apple video is based on the book the tv typewriter cookbook or something like that by Don Lancaster.
- dbcurtis 2y ago
  Exactly. I came here to say that. The amazing thing is Lancaster wrote that book before there was a pc of any kind to hook up to. But he showed very clearly how to generate NTSC monochrome video with a bucket of TTL chips. Such good times and good memories. SWTPC sold a kit of that TV Typewriter that I built. Not only Apple and SWTPC but Sol and mo doubt others basically cloned Lancaster’s design.

jandrese 2y ago

I think the Commodore PET used discrete TTL as well. This is first generation stuff for home computers, the costs are so high that manufacturers were highly incentivized to make graphics chips as soon as the technology was viable, right around 1979 or 1980. Anything made from then on is going to have a dedicated graphics chip of some kind just for the cost savings.

PaulHoule 2y ago
So did the other member of the "trinity", the TRS-80 model I. My mental picture is that the kind of display controller I'd like to build is about two large breadboards stuffed with 54xx chips. Such a thing is a bit simpler than a minimal CPU but not that much simpler because you need the stuff to interface with memory. I'd probably want to buy an oscilloscope and/or logic analyzer but maybe I could run it slow and use an AVR-8 Arduino to run test sequences. Almost everybody who builds throwback computers today uses either an FPGA or a microcontroller for the display controller. For instance https://github.com/fdivitto/FabGL https://github.com/fdivitto/FabGL is a highly flexible controller implemented for the ESP32 which can do tile-based graphics and sprites for games but also emulate an ANSI terminal. This is used in this SBC https://www.olimex.com/Products/Retro-Computers/AgonLight2/open-source-hardware https://www.olimex.com/Products/Retro-Computers/AgonLight2/o... which I am going to highly recommend because this machine is compatible with the old Z80 machines but has a real 24 bit mode with 24 bit registers and also performs an order of magnitude better than any Z80 machine did back in the day. Modern systems usually avoid the unified memory model that was popular back in the day but that also usually held back the performance of the CPU because one way or another the VDC was stealing cycles. The AgonLight board communicates with the display controller through a serial port, for instance. This thing http://www.commanderx16.com/ http://www.commanderx16.com/ has a memory mapped register for the address in video RAM the CPU wants to read/write and another for the data. The address register will auto-increment when access the data register so you can read or write video RAM at high speed just by repeatedly accessing the data register. The CX-16 uses an FPGA as a display controller https://github.com/X16Community/x16-docs/blob/master/X16%20Reference%20-%2009%20-%20VERA%20Programmer's%20Reference.md#chapter-9-vera-programmers-reference https://github.com/X16Community/x16-docs/blob/master/X16%20R...
- kjs3 2y ago
  two large breadboards stuffed with 54xx chips There's no need for mil-spec chips for this. Waste of money.
- beepill 2y ago
  > " I'd probably want to buy an oscilloscope and/or logic analyzer but maybe I could run it slow and use an AVR-8 Arduino to run test sequences." that's literally what i want to do because Im too broke for either lol you can squeeze an arduino's adc utilizing its timers and interrupts instead of using analogRead() in a loop: https://www.instructables.com/Girino-Fast-Arduino-Oscilloscope/ https://www.instructables.com/Girino-Fast-Arduino-Oscillosco... https://digibird1.wordpress.com/arduino-as-a-5m-sample-osciloscope/ https://digibird1.wordpress.com/arduino-as-a-5m-sample-oscil...
basementcat 2y ago
PET used a clone of the Motorola 6845 (also found in MDA and CGA adapters for the IBM PC). https://en.m.wikipedia.org/wiki/Motorola_6845 https://en.m.wikipedia.org/wiki/Motorola_6845 https://retrocomputing.stackexchange.com/questions/7117/how-did-the-commodore-pet-80-column-display-work https://retrocomputing.stackexchange.com/questions/7117/how-...
- PaulHoule 2y ago
  See also https://en.m.wikipedia.org/wiki/List_of_home_computers_by_video_hardware https://en.m.wikipedia.org/wiki/List_of_home_computers_by_vi... Note Don Lancaster's technique used for video in some computers https://www.tinaja.com/ebooks/cvcb1.pdf https://www.tinaja.com/ebooks/cvcb1.pdf such as https://en.wikipedia.org/wiki/ZX80 https://en.wikipedia.org/wiki/ZX80 In some strange sense this is like using a microcontroller to implement a CRTC except you're using the main CPU to do the work.
- jecel 2y ago
  The first couple of models used TTLs for the video circuit. These were replaced with the 6845 later on.

detourdog 2y ago

I lot of the Apple video is based on the book the tv typewriter cookbook or something like that by Don Lancaster.

dbcurtis 2y ago
Exactly. I came here to say that. The amazing thing is Lancaster wrote that book before there was a pc of any kind to hook up to. But he showed very clearly how to generate NTSC monochrome video with a bucket of TTL chips. Such good times and good memories. SWTPC sold a kit of that TV Typewriter that I built. Not only Apple and SWTPC but Sol and mo doubt others basically cloned Lancaster’s design.