Commander X16

22 hours ago, Perifractic said:

Here is Adrian's video about the troubleshooting:

Adrian Black is a class act.  What a gracious and generous video.  I have enjoyed his channel and hope he keeps producing new content for a long time.

This is an important step.  I hope folks in the community realize how much engineering work remains between "mostly runs on the bench" and "ready for production".

19 hours ago, BruceMcF said:

there could be a dedicated select line for device spaces 4-7 (of 0-7) for for cards 1, 2, 3, and 4, and a common select line for space 3 that goes to all four card slots, which some expansion cards can take advantage of for extra I/O space. Indeed, if there was a "enable use" select bit in the "native" address space, the "common extra" 32bits could be shared by cards if their drivers knew about each other.

Interesting assumption about common card space (I was wondering why is there 5 card spaces while board has only 4 slots).

I think somebody said something about possibility of cards communicating between each other. I think it was pretty long ago, may be on Facebook group. Or may be I'm imaginating things. 

12 minutes ago, Cyber said:

Interesting assumption about common card space (I was wondering why is there 5 card spaces while board has only 4 slots).



I think somebody said something about possibility of cards communicating between each other. I think it was pretty long ago, may be on Facebook group. Or may be I'm imaginating things. 

In one of the 2 "proto #2 working" videos, something is mentioned about five device spaces for four cards. I don't have time to listen to them again this afternoon, but IIRC, how that will work is not entirely settled.

On 1/7/2021 at 5:52 PM, Cyber said:

@lamb-duh @TomXP411



Ok, so I/O latches usually are physically outside the main RAM. We also call these latches "device registers". When we access them programmaticaly we actually don't care how they implemented physically, we just read or write I/O address in memory, thus communicate with device.



But speaking physically - what are these latches (registers) are? Is it internal part of actual device? Or is it just another separate RAM-like chip somewhere on board? Or it might be one or another?

Note that sometimes there ARE no registers, and the data lines drive logic directly when that address is written to. You might have a 2 to 4 decoder, connect the device select to the chip select for the decoder, a0 and a1 to the decoder input, and then $00-$03 inside the device address space generates four different select lines. Some of those select line might select logic chips to make use of the data input directly. If there are pull down resisters on those data lines, if it is read back, it would always return a $00, because the lines are essentially output only when the logic circuit is selected.

Or sometimes there is a write-only register and if your program needs to know what is in the register, it has to store the value itself, because it cannot be read.

it is possible that not all the address lines are connected ... you have a chip with two address lines, so you connect the device select line, a0 and a1, and $04-$07, $08-$0B, etc. all act like mirrors of $00-$03.

A lot of devices let you read register values back, because it's so handy ... and avoids errors when a software shadow register value is out of sync with the actual register ... but it is entirely the design of the chip or circuit that decides whether it does that.

 

43 minutes ago, BruceMcF said:

In one of the 2 "proto #2 working" videos, something is mentioned about five device spaces for four cards. I don't have time to listen to them again this afternoon, but IIRC, how that will work is not entirely settled.

I didn't pay atteantion to this, when listened for the first time. Thank you, I found it.

Quote from "Commander X16 Hardware Changes for Proto #2" video:

Quote

Also that freed up 5 expansion ranges for the I/O bus. So my idea was really, you know, you could obviously tie a card to a specific range if you wish. Or you could use a jumper and use multiple ones on a single card if you wanted to and now you just have one more available.

 

Quote from "Commander X16 Hardware Changes for Proto #2" video:

Quote

I'm inviting someone to plug a 950 watt Corsair power supply into this board and perform some pretty incredible arc welding across the pins or frying traces on the board and all that kind of fun stuff, so currently there's pretty much no current limiting.

I see I'm a missing a point here. I know that every component has its own eaxct current drain, so the whole board will also drain needed current only, even if PSU can provide more. I know that PSU might be too low on power, when board drain more current, than PSU can provide. But how can it be vice versa, how can it be too much power?

Quote from "Commander X16 Hardware Changes for Proto #2" video:

I'm inviting someone to plug a 950 watt Corsair power supply into this board and perform some pretty incredible arc welding across the pins or frying traces on the board and all that kind of fun stuff, so currently there's pretty much no current limiting.

I see I'm a missing a point here. I know that every component has its own eaxct current drain, so the whole board will also drain needed current only, even if PSU can provide more. I know that PSU might be too low on power, when board drain more current, than PSU can provide. But how can it be vice versa, how can it be too much power? It’s too much power when you make a mistake and fry something catastrophically. We are looking at implementing perhaps self resetting fuses or something.   Sent from my iPhone using Tapatalk

Isn't this answered by our beloved formula U=RI => I=U/R?

That is, the amount of current drawn by a circuit depends on the voltage and the overall resistance, not how many watts the PSU may supply.

12 minutes ago, Stefan said:

Isn't this answered by our beloved formula U=RI => I=U/R?



This is, the amount of current drawn by a circuit depends on the voltage and the overall resistance, not how many watts the PSU may supply.

Yes. That's why I'm confused as well. But if I understood @Lorin Millsap correctly, if you make a mistake, i.e. make a short circuit accidently, then the scale of damage will be proportional to PSU power.

11 minutes ago, Cyber said:

Yes. That's why I'm confused as well. But if I understood @Lorin Millsap correctly, if you make a mistake, i.e. make a short circuit accidently, then the scale of damage will be proportional to PSU power.

True.

Also answered by I=U/R => During a short R is close to 0 Ohm and I is close to infinity Amps (but in reality the amount of amps provided by the PSU).

Almost everything I know about electricity is contained within those three letters ?