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Kevin Williams

Commander X16 Hardware - March 2021 Update

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Hey Everyone, 

  I just made a new video showing some updates on the Commander X16 second Prototype.  I've been working on a few modifications, and getting them incorporated into a daughter-board.  The board was updated, and sent over to Michael Steil to work on the kernal.  At this point, he should have what will be pretty close to the final HW.  I cover a few topics, so please take a look if you have a second and thanks for taking the time.

Take care,
-Kevin

https://youtu.be/T5vjnBYGp2w

X16-Daughter-YouTube-Thumbnail1.jpg

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Great job on getting the NMI/Restore working! The lack of RunStop/Restore has beeing driving me nuts!  🙂

Also, the use of an MCU for the power control circuitry is pretty clever. It looks like that solves a few small problems and will make the power supply more stable. 

 

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Thanks for the update - that looks like some fun was had in the making of the video!

Creative handling of the reset button, as well - that approach works really well, I think.  Similar approach to power buttons on most PCs.

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I'm a bit lost on the concern with the PWR_OK signal.

If there is ever a PWR_OK falling edge that is a problem and PS_ON should be quickly deasserted (or tri-stated will work too, I think, because it has an internal pull-up).

In modern systems the concern is that the CPU + GPU combination can draw hundreds of watts so it is necessary to wait for PWR_OK to allow enough energy to build up in the converter's coil(s) so that there isn't either an inrush overcurrent or brown out issue. In the X16's case, it appears all that is done is holding the 65C02 in reset until PWR_OK is asserted (I didn't see any power gating circuitry anywhere in the photo). This isn't providing much inrush current protection over idle current draw so I'm wondering why RESB isn't just driven directly by PWR_OK? It seems like the only thing you need to do is have a circuit that resets PS_ON if PWR_OK deasserts while PS_ON is asserted (obviously being careful to edge detect PWR_OK since it is going to be at the deasserted level for a short bit after PS_ON is first asserted).

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I like the idea of a programmable microcontroller especially as it is only for power... but imagine to possabilities? What about a LCD driver or even remote control or WIFI??

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1 hour ago, Trax81 said:

I like the idea of a programmable microcontroller especially as it is only for power... but imagine to possabilities? What about a LCD driver or even remote control or WIFI??

The X16 design has been very expandable already, so lots of these ideas have been floating around for quite some time now. You probably wouldn't want to use the ATtiny84 for that, though.

But I really like the fact that we now have I2C, too. (I'm hoping for KERNAL support here - writing your own I2C bit-banging code was obviously already possible before.)

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Posted (edited)

The two I2C bus lines from the VIA and the serial shift register lines from the VIA plus VCC and Ground would make a nice little connector on the back of the case, next to a Centronics style parallel port connector.

(I also saw whinging in the YouTube comments about the CX16 now having a microcontroller that is powerful enough to be the basis for a more powerful retro computer than the CX16 itself ... I am guessing they have not looked at the ATtiny24/44/84 datasheet.)

Edited by BruceMcF
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1 hour ago, BruceMcF said:

(I also saw whinging in the YouTube comments about the CX16 now having a microcontroller that is powerful enough to be the basis for a more powerful retro computer than the CX16 itself ... I am guessing they have not looked at the ATtiny24/44/84 datasheet.)

This. Many moons ago I made an Arduino-based PID controller for my espresso machine, then realized it was overkill and ported the thing to an ATtiny84. It's a capable microcontroller for small tasks but no powerhouse. I'm starting to believe many people lump in ATMEGAs, their smaller cousins and Raspberry Pi together with regards to capabilities and performance.

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2 hours ago, BruceMcF said:

I am guessing they have not looked at the ATtiny24/44/84 datasheet.

Anybody who needs more than 128 bytes of RAM is just greedy. It was good enough for the Atari 2600!

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7 hours ago, SlithyMatt said:

Anybody who needs more than 128 bytes of RAM is just greedy. It was good enough for the Atari 2600!

Yes, it's outrageous that an ATtiny84 is being used when the much more frugal ATtiny24 has a whole 0.125KB of RAM AND EPROM, and KILOBYTES on chip flash storage. (I almost said "multiple kilobytes", but realized that once you hit "kilobytes", it isn't the one that has multiples of that.)

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7 hours ago, SlithyMatt said:

Anybody who needs more than 128 bytes of RAM is just greedy. It was good enough for the Atari 2600!

Also the KENBAK-1, a huge commercial success. 

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