Re: [M100] Rechargeable batteries

[Brian Brindle]

May not be the direction you are looking for, but I use one of those cheap
USB battery banks with a USB to 6v power adapter. They are pretty easy to
make but show up on Ebay pre-made quite often. I can run my M100 and some
peripherals for months without having to re-charge and fall back to the AAs
when I have to.

Brian


On Mon, Jun 20, 2022 at 3:13 PM  wrote:

>
>
>
>
> >>Also, I believe there were previous discussions about replacing the
> memory ni-cad with a super capacitor.
>
>
>
> I have done that on one M100. It works fine but does not last nearly as
> long as a new NiMh battery.
>
>
>
> Jeff Birt
>

Re: [M100] the function of A* in M100/T102

[Stephen Adolph]

That's interesting.  Can easily see how that would be.

Now, notice that the main rom had no such function.  The chip select for
the main rom happens right away with no delay.

Does the rom have no time dependent power consumption?  Or is the main rom
just so slow?

My guess is a bit of both, because T102 has a much faster main rom but the
chip select circuit is the same as M100.



On Monday, June 20, 2022,  wrote:

> Thinking about this some more jogged the memory that the idea of a chip
> enable came from HP first desktop scientific calculator. It was transistor
> based and used so much power that the guy who invented it came up with an
> enable signal for various parts of the system so everything did not need to
> be powered up at one. He said HP made a lot more licensing the chip enable
> patent than they ever did on calculators.
>
>
>
> Jeff Birt
>
>
>
> *From:* M100  *On Behalf Of *
> bir...@soigeneris.com
> *Sent:* Monday, June 20, 2022 10:57 AM
> *To:* m...@bitchin100.com
> *Subject:* Re: [M100] the function of A* in M100/T102
>
>
>
> Wow, Steve what great detective work. I love thigs like this, when one
> spends ages trying to figure out why something was designed a certain way
> and then you have that ‘Aha!’ moment. A very good example of the art of
> engineering…
>
>
>
> Jeff Birt
>
>
>
> *From:* M100  *On Behalf Of *Stephen
> Adolph
> *Sent:* Saturday, June 18, 2022 8:46 AM
> *To:* m...@bitchin100.com
> *Subject:* [M100] the function of A* in M100/T102
>
>
>
> I've often wondered about the purpose of the A* signal on the M100.
>
>
>
> A* is used to control the internal RAM.  It drives the timing for the RAM
> chip selects.  Also, since the RAM are wired with OE grounded, whenever A*
> is high, the RAM will try to immediately output data, unless the processor
> is writing data to it.
>
>
>
> A
>
>
>

Re: [M100] Rechargeable batteries

[birt_j]

 

 

>>Also, I believe there were previous discussions about replacing the memory
ni-cad with a super capacitor.

 

I have done that on one M100. It works fine but does not last nearly as long
as a new NiMh battery. 

 

Jeff Birt

Re: [M100] Rechargeable batteries

[you got me]

One option might be to install 5 ni-mh cells. 4 in the regular place and a 5th 
inside of the m100. Then have a ni-mh charging circuit (widely available) in 
line with the 6v adapter socket of the m100. So, while the m100 is plugged in, 
it charges the batteries.

Also, I believe there were previous discussions about replacing the memory 
ni-cad with a super capacitor.

From: M100  on behalf of Allan Zieser 

Sent: Monday, June 20, 2022 12:55 PM
To: m...@bitchin100.com 
Subject: [M100] Rechargeable batteries


I have noticed that with rechargeable batteries the active life for the Model 
100 is shorter. This is because most rechargeable batteries follow a curved 
path for power drain. They only maintain the 1.5 volts for s short time then 
tend to drop lower for the remainder of their power drain. When the power drops 
low enough the Model 100 activates the low power light and then goes down.



There are some exceptions to this discharge path. The EBL rechargeable 
batteries hold the 1.5 voltage across their drain, however then they drop off 
sharply causing a shutdown when they are at the end of the discharge cycle. Not 
really an issue for me as I use the Rex and Jeff’s backpack so I can save often 
on projects. Just some of the tradeoffs I have noticed when using rechargeable 
batteries.



In regards to the backup battery, the advantages do outweigh the disadvantages. 
If you are only running on installed batteries then the backup battery will 
recharge from them continuously, reducing the battery life. However if you use 
a wall outlet or usb power cable then it will extend the life of the batteries 
by charging the backup off of the power cable instead of the installed 
batteries.



I have considered installing NiCad’s, however this requires a little soldering, 
so I am not sure if it is worth it. For now I just use a combination of the EBL 
batteries and a USB power cable I found on Ebay that works really well.



Just my observations on this. Please correct me if I am wrong in any of this.  
Have a great week!



-Allan Zieser

Re: [M100] the function of A* in M100/T102

[birt_j]

Thinking about this some more jogged the memory that the idea of a chip enable 
came from HP first desktop scientific calculator. It was transistor based and 
used so much power that the guy who invented it came up with an enable signal 
for various parts of the system so everything did not need to be powered up at 
one. He said HP made a lot more licensing the chip enable patent than they ever 
did on calculators.

 

Jeff Birt

 

From: M100  On Behalf Of 
bir...@soigeneris.com
Sent: Monday, June 20, 2022 10:57 AM
To: m...@bitchin100.com
Subject: Re: [M100] the function of A* in M100/T102

 

Wow, Steve what great detective work. I love thigs like this, when one spends 
ages trying to figure out why something was designed a certain way and then you 
have that ‘Aha!’ moment. A very good example of the art of engineering…

 

Jeff Birt

 

From: M100 mailto:m100-boun...@lists.bitchin100.com> > On Behalf Of Stephen Adolph
Sent: Saturday, June 18, 2022 8:46 AM
To: m...@bitchin100.com  
Subject: [M100] the function of A* in M100/T102

 

I've often wondered about the purpose of the A* signal on the M100.

 

A* is used to control the internal RAM.  It drives the timing for the RAM chip 
selects.  Also, since the RAM are wired with OE grounded, whenever A* is high, 
the RAM will try to immediately output data, unless the processor is writing 
data to it.

 

A

 

Re: [M100] the function of A* in M100/T102

[birt_j]

Wow, Steve what great detective work. I love thigs like this, when one spends 
ages trying to figure out why something was designed a certain way and then you 
have that ‘Aha!’ moment. A very good example of the art of engineering…

 

Jeff Birt

 

From: M100  On Behalf Of Stephen Adolph
Sent: Saturday, June 18, 2022 8:46 AM
To: m...@bitchin100.com
Subject: [M100] the function of A* in M100/T102

 

I've often wondered about the purpose of the A* signal on the M100.

 

A* is used to control the internal RAM.  It drives the timing for the RAM chip 
selects.  Also, since the RAM are wired with OE grounded, whenever A* is high, 
the RAM will try to immediately output data, unless the processor is writing 
data to it.

 

A* is logically the NAND of /WR and /RD.  A* is '1' whenever a read or write is 
happening. So the ram chip selects never get enabled until well into the 
processor cycle, far later than it could be based on IO/M and address lines.

To me this has always been a bit peculiar.  Chip selecting, and the function of 
reading or writing have separate timings and can be done separately.  

 

Also, I think A* is used to enable "external RAM" on the M100.  I think that is 
how the PG Designs ram bank products work for example - by controlling A*.

 

So, why did the M100 designers choose to delay the chip select for the RAM?

 

As I have been playing around with 5MHz hacking on these things I have found 
that, in order to speed up the computer, one has to fiddle with A*.  Generally, 
A* has to be enabled EARLIER in the processor cycle in order to give the RAM 
time to respond at the higher speed.

 

I've noticed that the computer power consumption is quite sensitive to the 
actual timing of A*.  The earlier I enable A*, the higher the current.

 

Here's some numbers:

At 2.5 MHz (stock speed) the RAM in my M100 consumes about 2.3 mA out of the 50 
mA of the machine overall.  This is with a "stock" A* signal.

 

In the extreme case of setting A* permanently on (hard wired to 5V) , at 5MHz 
the RAM current shoots up to 20mA!  and the M100 is consuming   85 mA.

(not great right?)

 

If I do a bit of work, I can generate an A* signal that minimizes RAM current 
to 4.3 mA while operating at 5MHz.  Much better!  this keeps the overall M100 
power to <70mA @5MHz.

 

Re-reading various datasheets, and thinking about memory power ... I think the 
M100 hardware designers were using A* to significantly limit the amount of time 
that the RAM chips were enabled.  By doing so, they dramatically reduced the 
overall memory power.  This of course makes sense for a battery powered 
computer.

 

This was an interesting ah-hah.  In retrospect, it makes perfect sense once you 
realize that "on" time is driven by chip-select and that drives power.

 

And the result of all this twiddling is that my 5MHz hacks are quite a bit 
lower power.

 

I have some new PCBs on the way.  These boards piggy back on the CPU, and 
provide the faster clock.  Now they also generate a new A* signal for the RAM.

 

In terms of computer power, I expect the following.

1) for a FIXED (ie permanent) 5MHz conversion, the increase in current should 
be 18mA

2) for a SWITCHABLE conversion, the increase in current should be 3mA in 2.5M 
mode and 21 mA in 5M mode.

 

Standard system RAM is usable in both T102 and M100.

The only memory part that needs to be changed is the M100 ROM, which is very 
very slow.  So 5MHz must have an EPROM conversion or similar.

 

 

 

 

 

 

 

Re: [M100] Rechargeable batteries

[birt_j]

I have been trying out AA sized lithium polymer batteries. They have the
charge control and voltage regulation built into each battery a solid 1.5V
out until it's flat.  One downside I have noticed is that if you have one
flat battery and 3 good ones in series it will try to force the current
though the dead cell and heat it up. This can happen with any battery
chemistry though. 

A colleague mentioned a particular brand of these which he thought were
better (this is his research area, so I trust him), but I forget the brand
name. When I find out again, I will compare them with the Tenavolts brand
I'm testing now.

 

Jeff Birt

 

From: M100  On Behalf Of Allan Zieser
Sent: Monday, June 20, 2022 7:56 AM
To: m...@bitchin100.com
Subject: [M100] Rechargeable batteries

 

 

There are some exceptions to this discharge path. The EBL rechargeable
batteries hold the 1.5 voltage across their drain, however then they drop
off sharply causing a shutdown when they are at the end of the discharge
cycle. Not really an issue for me as I use the Rex and Jeff's backpack so I
can save often on projects. Just some of the tradeoffs I have noticed when
using rechargeable batteries. 

 

-Allan Zieser

 

Re: [M100] Rechargeable batteries

[John R. Hogerhuis]

Data loss has never been an issue for me.

Internal battery protects the ram for quite a while.

And I get about 20 hours of use out of Eneloop batteries.

If you're actively using it you just have spare batteries topped up and
swap them when the out.

If I am not actively using it, it could weeks/months without losing ram
contents because the main batteries keep the backup charged.

If the backup batery is not good or there is some hardware problem YMMV

I think I've only ever lost data because of corruption due to software
faults.

 -- John.

[M100] UK Tandy 200 part number

[Stephen Adolph]

>From an ebay auction;
I think that says 26-3860H.  Meaning, this must be a "no modem" variant?
Steve

[image: t200 uk.PNG]

[M100] Rechargeable batteries

[Allan Zieser]

I have noticed that with rechargeable batteries the active life for the Model 
100 is shorter. This is because most rechargeable batteries follow a curved 
path for power drain. They only maintain the 1.5 volts for s short time then 
tend to drop lower for the remainder of their power drain. When the power drops 
low enough the Model 100 activates the low power light and then goes down.

There are some exceptions to this discharge path. The EBL rechargeable 
batteries hold the 1.5 voltage across their drain, however then they drop off 
sharply causing a shutdown when they are at the end of the discharge cycle. Not 
really an issue for me as I use the Rex and Jeff's backpack so I can save often 
on projects. Just some of the tradeoffs I have noticed when using rechargeable 
batteries.

In regards to the backup battery, the advantages do outweigh the disadvantages. 
If you are only running on installed batteries then the backup battery will 
recharge from them continuously, reducing the battery life. However if you use 
a wall outlet or usb power cable then it will extend the life of the batteries 
by charging the backup off of the power cable instead of the installed 
batteries.

I have considered installing NiCad's, however this requires a little soldering, 
so I am not sure if it is worth it. For now I just use a combination of the EBL 
batteries and a USB power cable I found on Ebay that works really well.

Just my observations on this. Please correct me if I am wrong in any of this.  
Have a great week!

-Allan Zieser