32k expansion works through speech synth without external power??

[Cory_]

I just got a speech synth and I've noticed that my 32k sidecar works through the speech synth module without the external power supply plugged in. Running the memory test program I found on this forum shows all 32k as PASSED, and 32k games seem to work.

 

Did the previous owner already mod this thing, or do I not understand something? I thought the speech synth doesn't have power passthrough.

[+arcadeshopper]

I just got a speech synth and I've noticed that my 32k sidecar works through the speech synth module without the external power supply plugged in. Running the memory test program I found on this forum shows all 32k as PASSED, and 32k games seem to work.
 
Did the previous owner already mod this thing, or do I not understand something? I thought the speech synth doesn't have power passthrough.

Either your speech is modded or there's just enough voltage leak though other lines to make it work. If it's the latter I wouldn't trust it to work reliably.

Sent from my Pixel 6 Pro using Tapatalk

[+hloberg]

wasn't it a wire soldered to the underside of the speech syn to mod it for bypass of power. that could be a way he could check.

[Cory_]

I just checked, no wires. It looks stock.

Edited January 23, 2022 by Cory_

[+arcadeshopper]

Then I wouldn't trust it to work correctly

Sent from my Pixel 6 Pro using Tapatalk

[+jedimatt42]

As the designer, yes, I apologize to the community that it is possible for these to work at all in this situation. It is not by design. All the chips are being run 'out of spec' in this case. It is probably also resulting in extra current flow through the address bus buffers in the 4A console. So running it this way is likely to shorten the lifespan of the 74LS244 chips on the motherboard. Again, I apologize. 

[+OLD CS1]

@jedimatt42 Well, the warnings are all over the place. If anyone kills their system because they cannot follow directions, I feel no sorrow for them.

[Stuart]

From the history of the ARM processor:

 

Today one of the most significant features of the ARM family is its low power consumption. But that hadn't been an initial goal, according to Furber. 'We designed the ARM for an Acorn desktop product, where power isn't of primary importance. But it had to be cheap. Cheap meant it had to go in a plastic package, plastic packages have a fairly high thermal resistance, so we had to bring it in under 1W.'

 

The power test tools they were using were unreliable and approximate, but good enough to ensure this rule of thumb power requirement. When the first test chips came back from the lab on the 26 April 1985, Furber plugged one into a development board, and was happy to see it working perfectly first time.

 

Deeply puzzling, though, was the reading on the multimeter connected in series with the power supply. The needle was at zero: the processor seemed to be consuming no power whatsoever.

 

As Wilson tells it: “The development board plugged the chip into had a fault: there was no current being sent down the power supply lines at all. The processor was actually running on leakage from the logic circuits. So the low-power big thing that the ARM is most valued for today, the reason that it's on all your mobile phones, was a complete accident."

[Cory_]

9 hours ago, OLD CS1 said:

@jedimatt42 Well, the warnings are all over the place. If anyone kills their system because they cannot follow directions, I feel no sorrow for them.

The less than 5 minutes that it ran this way isn't gonna do anything. It's still working fine and I plan on using it correctly, of course. I was just curious why it was working at all after initially setting it up wrong by mistake.

 

There's a jumper on the sidecar you have to set to switch from internal power to the power brick and I didn't set it right.

Edited January 23, 2022 by Cory_

[+OLD CS1]

2 hours ago, Cory_ said:

The less than 5 minutes that it ran this way isn't gonna do anything.

That was meant generally.  We have at least one instance of someone here asking the same question and outwardly expressing that he will continue to operate the device against recommendations.  Where there is one, there are likely more who will either accept this operating condition with disregard for instructions, or will, like you, ask about it then, unlike you, decide to continue on against explicit recommendations.

[Cory_]

6 minutes ago, OLD CS1 said:

We have at least one instance of someone here asking the same question and outwardly expressing that he will continue to operate the device against recommendations.

How obstinate of them. Thanks for the help everyone, and sorry for asking a duplicate question.

[+OLD CS1]

Just now, Cory_ said:

How obstinate of them. Thanks for the help everyone, and sorry for asking a duplicate question.

We would rather people ask the question than carry on and unnecessarily kill their systems.

[+OLD CS1]

@Cory_ And, btw, welcome to the forum.

[HOME AUTOMATION]

20 minutes ago, Cory_ said:

How obstinate of them.

I believe that I take umbrage with regard to this statement ...Is it not the board that's behaving obstinately, for continuing to operate out of specs.?

[+OLD CS1]

32 minutes ago, HOME AUTOMATION said:

I believe that I take umbrage with regard to this statement ...Is it not the board that's behaving obstinately, for continuing to operate out of specs.?

I mean, we have told it that it is not operating within specifications.  So who, indeed, would be at fault: the stubborn user or the stubborn equipment?

[HOME AUTOMATION]

I suppose that my lack of enthusiasm directs towards the need to assign blame, rather than the recognition of an opportunity to explore the possible ramifications in a less diminutive light! Perhaps an outcrop of my inclinations with regard to fault-testing in general.

 

[Ed in SoDak]

[oracle_jedi]

Related question then...

 

Is there any reason NOT to add the jumper to the speech synthesizer to power the 32K board?   Am I stressing the power supply driving both peripherals?

[+jedimatt42]

Texas Instruments only rated the +5v pin on the sideport for 50 milliamps.  Several of us have ritually abused that rating, but it all depends on your copper. Years ago when I was making the 32k boards, I used the 74HCT chips to keep the current demand low. Someone would have to crack things open, and actually measure the load given things like FinalGROM99's plugged in, F18A's and all the mess... Anecdotally, but not scientifically, I feel like when I ran in the config you speak of, @oracle_jedi, my FinalGROM99 had more trouble reading the SD card on power up... 

[Sergioz82]

I'm not sure I understood it right: is this issue about original ram expansion only or modern ones too?

I didn't know this issue, I thought T.I designed the expansion port in cascade power supply. 

 

I recently upgraded my TI with speech synthetizer and modern 32K expansion and they both work fine. 

The ram expansion also has a led to indicate it's in use and it lights up.

[+OLD CS1]

32 minutes ago, Sergioz82 said:

I'm not sure I understood it right: is this issue about original ram expansion only or modern ones too?

I didn't know this issue, I thought T.I designed the expansion port in cascade power supply. 

TI's side-car and PEB 32k expansions have their own power sources.

[+jedimatt42]

6 hours ago, OLD CS1 said:

TI's side-car and PEB 32k expansions have their own power sources.

 

I assume the answers to this sort of thread are unsatisfying because it hasn't been worth anyone's time to do the work required for definitive statements. So all we can give you is insight into intentions and let people assess for themselves the risk.

[+arcadeshopper]

 
I assume the answers to this sort of thread are unsatisfying because it hasn't been worth anyone's time to do the work required for definitive statements. So all we can give you is insight into intentions and let people assess for themselves the risk.

It's amazing what people will do to avoid a 10$ power supply

Sent from my Pixel 6 Pro using Tapatalk

[+OLD CS1]

18 minutes ago, arcadeshopper said:

It's amazing what people will do to avoid a 10$ power supply

Heck, I power mine with a good USB power source and appropriate barrel connector.

[oracle_jedi]

1 hour ago, arcadeshopper said:

It's amazing what people will do to avoid a 10$ power supply

Sent from my Pixel 6 Pro using Tapatalk
 

Or maybe it a desire to reduce desk spaghetti and free up power outlets.  

 

I love my Corcomp 9900.  But once I have the TI, the Corcomp with its insanely huge wall-wart, the Tex'n'Treasure 3.5 floppy disk with its brick and maybe the Gotek aswell, the desk looks like the fire dept at a major incident and I've lost 6 or more outlets.  I love the FinalGrom and @jedimatt42 32K board precisely because I can quickly set up the TI and play some awesome games. 

 

I mean if this was really about people too cheap to spring for a $10 power supply we'd all just emulate.