Hi there,

I am working on a small project, to build a Commodore PET replica using a minimum set of still available parts, but feature rich in the sense that it can do 80 columns and run at higher speeds.

My latest udate video is here https://youtu.be/7ZddamWx9Io

The project will ultimately end up on github, but only when I have managed to make the CPU work with RAM, ROM and some I/O sufficiently correctly...

Here's are the previous videos (note the new one is still unlisted): https://www.youtube.com/playlist?list=P ... fhNH4IPWSx

Pls let me know what you think!

André

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Neat, looks like a good start to the project. What clock frequency are you targeting, and what are you planning on using as the keyboard interface?

So, beyond doing 80 columns, it seems to have 512 KB of memory, built-in bank switching, and not least a 65816 CPU running at that higher speed! Certainly an interesting project. And I also agree with you that the MiniPET's use of an Atmel MCU to emulate the original PET's video system feels like a bit of a cheat, and the CPLD less so. (Also, the MiniPET's dual-ported RAM is moderately expensive and rare.) Though I'd still like to see it done one day without even the CPLD.

However, I wonder about the name. Your system seems to be not smaller than but considerably larger than the MiniPET in terms of capabilities, and I'm guessing the BOM cost is also going to be more expensive, or at least around the same price. (Correct me if I'm wrong about that.)

"Super MiniPET" comes to mind, but I'm sure we all see how that could get confusing. Unless you care to add a 6809 to the board? :-)

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Curt J. Sampson - github.com/0cjs

The problem of doing this without a CPLD (or some other higher-integrated video / glue logic chip) is, that you'll end up with a PET board basically (maybe optimized but still).
Admittedly, if you optimize to a SRAM, and a large ROM, use BE instead of separate drivers lots of the glue gets optimized away, but still...

I'm targeting 8MHz CPU speed outside the visible screen area, but not all of this memory bandwidth is available during screen fetches. In 80col charrom mode it will be reduced to 4MHz during the screen fetch (2 MHz character fetch, 2 MHz char"rom" fetch from RAM, rest 4MHz for CPU)


Thanks, yes I was actually wondering why the MiniPET was so restricted in capabilities - one trigger to work on that project.

About the BOM - I am not sure what is more expensive. The CPLD is basically 40€ - and the rest should be on the MiniPET just as well - the CPU, VIA, PIAs, I/O buffers, Voltage control.

My current version is still using the mc3446 which are prohibitively expensive, but I'll plan to use 74ls640-1 that can drive IEEE488 compatible currents and are still available.
Also, my board is - if I judge the pictures correctly - quite a bit smaller than the MiniPET (thus also the name).
The I/O part is basically 1:1 copy of this board http://www.6502.org/users/andre/csa/petio/index.html - there is room for optimization, I think I can optimize away 2 TTL chips, even without sacrificing the fact that it can actually run as a _drive_ on the IEEE488 board due to its ATN Acknowledge circuit. Also, the IEEE488 connector is basically unobtainable... the next version will have card edge connectors, plus flat ribbon cable connectors, but no real IEEE488.
I don't have tape drive transistors, but still 5V for hopefully the "usual" extensions.
The next version will also have an additional 74HCT245 as voltage converter between CPLD and CPU.

I just hope to stay under the limit of a Eurocard (160x100mm) as this is what my version Eagle can do max (an old not-for-profit version).



Haha. No that chip is too slow

Du you know about the Micro-MMF (uMMF)?

Btw: here's an update video: https://youtu.be/7ZddamWx9Io

André

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Keyboard is a real PET keyboard (I have ordered TexElec Petskeys) . Alternatively (with an adapted editor ROM) a C64 keyboard.

Actually I'm thinking if I should build it into my clear case C64-C case

Power will most likely be something like USB-Micro (as long as my bench power supply confirms it stays under 0.5A), or some other standard 5V supply.

As the CPU is the most "intelligent" part, I'm not into having a USB controller that then emulates the C64/PET keyboard. I'd rather think of adding a USB interface directly (via SPI), and then run my USB65 stack on the 65816.

André

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Another milestone in for the MicroPET: https://youtu.be/C_IKVLF-Ad8

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Cool!

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Building the TexElec Petskey keyboard for it: https://youtu.be/GUAeGa1AKvU

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

... and here the first official release: https://youtu.be/Ak7JMfqDNnE

The source code for the MicroPET (VHDL, schematics, ROM code) is on github: https://github.com/fachat/MicroPET

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Very nice!

Now you can select PET ROM version during boot, and 80column mode (i.e. 8032 replica) works: https://youtu.be/t1UKwnFlFkE
Although visicalc does not yet full load... Maybe undocumented opcodes?

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Now there is VGA output: https://youtu.be/gQuWTnop3e0

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Here is another update. The Micro-PET now boots from SPI flash, and some benchmarks are there too: https://youtu.be/egORnK1ZwBg

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Another update on the Micro-PET, with an outlook to release 2 of it: https://youtu.be/hM8lFS1gt0Q

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Here is the first video on release 2 of the Micro-PET: https://youtu.be/TSDv9O6bYw8

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/