Power supply

Falken · Post by **Falken** » Sat Apr 02, 2022 12:46 am

As I read people buying 300W power supplies for this project I wondered: How many Watts or Amps does an X16 actually need? I could not find it in the specs but maybe I looked at the wrong place. Does someone have an answer?

Thank you.

Scott Robison · Post by **Scott Robison** » Sat Apr 02, 2022 1:18 am

On 4/1/2022 at 6:46 PM, Falken said:

As I read people buying 300W power supplies for this project I wondered: How many Watts or Amps does an X16 actually need? I could not find it in the specs but maybe I looked at the wrong place. Does someone have an answer?

Thank you.

1.21 gigawatts with the flux capacitor upgrade. Not sure about a stock board though.

TomXP411 · Post by **TomXP411** » Sat Apr 02, 2022 3:19 am

On 4/1/2022 at 5:46 PM, Falken said:

As I read people buying 300W power supplies for this project I wondered: How many Watts or Amps does an X16 actually need? I could not find it in the specs but maybe I looked at the wrong place. Does someone have an answer?

Thank you.

The Commodore 64 uses around 1-2 amps on the 5V rail, depending on the generation and attached peripherals. I expect the CX16 to be similar.

Falken · Post by **Falken** » Sat Apr 09, 2022 12:47 am

On 4/2/2022 at 5:19 AM, TomXP411 said:

The Commodore 64 uses around 1-2 amps on the 5V rail, depending on the generation and attached peripherals. I expect the CX16 to be similar.

Would that mean you could power the X16 with a USB power supply? They are easily obtainable in the 2 Amp range. Might also make the whole system cheaper.

Just a thought.

kelli217 · Post by **kelli217** » Sat Apr 09, 2022 3:01 am

On 4/8/2022 at 7:47 PM, Falken said:

Would that mean you could power the X16 with a USB power supply? They are easily obtainable in the 2 Amp range. Might also make the whole system cheaper.

Just a thought.

For the self-contained one, sure. The one with expansion slots will need more.

Assuming there will be a version with expansion slots. Poll or no poll, we're still at the mercy of the supply chain, and in the end it's David's decision what to build.

Wavicle · Post by **Wavicle** » Sat Apr 09, 2022 11:56 pm

At the command prompt with a flashing cursor (not performing any stressful workloads), my bread-boarded computer w/ similar hardware (VERA, 65C02, 2x VIA, 2x SRAM, 1x NAND flash, 8MHz clock, all discrete 7400-series address decoding logic, PS/2 keyboard) pulls 0.072A at 5V, or 350mW @2MHz while sitting at the READY prompt. If the real CX16 pulled twice that, it would still be under 1 watt.

Edit: I just cranked the clock up to 8MHz and the current measured was 0.114A, so ~0.570mA. If the real CX16 pulled twice that it would be OVER ONE WATT!!! All signs point to very lower power consumption.

Jeff Pare · Post by **Jeff Pare** » Sun Apr 10, 2022 4:14 am

Isn't part of the reason for an ATX power supply having +/-12V for serial communication? I also think these voltages were available on the expansion slots.

BruceMcF · Post by **BruceMcF** » Sun Apr 10, 2022 2:00 pm

On 4/10/2022 at 12:14 AM, Jeff Pare said:

Isn't part of the reason for an ATX power supply having +/-12V for serial communication? I also think these voltages were available on the expansion slots.

Yes, it does simplify making a UART as a true RS-232C interface, with the longer cable runs that supports ...

... but I think the other part was because micro-ATX and mini-ITX cases will likely come with an ATX PS.

Edmond D · Post by **Edmond D** » Sun Apr 10, 2022 5:08 pm

On 4/9/2022 at 9:14 PM, Jeff Pare said:

Isn't part of the reason for an ATX power supply having +/-12V for serial communication? I also think these voltages were available on the expansion slots.

A MAX 232 chip uses a charge pump to generate levels that work for RS-232 transmutation with only a 5 V chip power supply. See https://en.wikipedia.org/wiki/MAX232 and then onward to the data sheets.

In industrial applications, having a maximum swing of voltage for signalling is great, as these environments usually have high noise and long cable runs. In an hobby/office environment signalling voltages can be a lot less and still work well.

BruceMcF · Post by **BruceMcF** » Sun Apr 10, 2022 9:26 pm

On 4/10/2022 at 1:08 PM, Edmond D said:

1] A MAX 232 chip uses a charge pump to generate levels that work for RS-232 transmutation with only a 5 V chip power supply. See https://en.wikipedia.org/wiki/MAX232 and then onward to the data sheets.

[2] In industrial applications, having a maximum swing of voltage for signalling is great, as these environments usually have high noise and long cable runs. In an hobby/office environment signalling voltages can be a lot less and still work well.

[1] Why I said "simplify" instead of "allow".

[2] Yes, if there is a serial connection to a computer where the hobby bench is in the basement and the computer is in the office upstairs, it might matter ... otherwise TTL is probably good enough. But, OTOH, for some people it might matter because a "proper" RS-232C connection is what they HAD, "back in the day".