Is the Everdrive safe to use on the NES/Famicom?

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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Salduchi
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Is the Everdrive safe to use on the NES/Famicom?

Post by Salduchi »

I was thinking about getting an Everdrive N8 Pro for my Famicom but I was wondering if they are safe to use since these carts have a lot of new tech in them. I assume they draw more power than standard carts and cause more heat to build up in the console. Famicom is 5v (I think) and most flash carts I’ve seen are 3.3v. Not sure about the Everdrive though. Anyone know anything about this?
Catyak
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Re: Is the Everdrive safe to use on the NES/Famicom?

Post by Catyak »

Salduchi wrote: Mon Sep 25, 2023 2:07 pm I was thinking about getting an Everdrive N8 Pro for my Famicom but I was wondering if they are safe to use since these carts have a lot of new tech in them. I assume they draw more power than standard carts and cause more heat to build up in the console. Famicom is 5v (I think) and most flash carts I’ve seen are 3.3v. Not sure about the Everdrive though. Anyone know anything about this?
All of the current Everdrives (including the N8 Pro) have dedicated hardware that converts 3v signals to 5v signals and vice versa, this is also known as voltage level translation, or level translation. This hardware cleanly resolves the logic voltage issue that some cheaper modern (flash)carts suffer from.
Can't comment about the power draw issue in more detail, as I haven't seen detailed measurements of cartridge power draw that include the NES Everdrives, aside from the fact the N8 Pro consumes more power than the N8.
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aquasnake
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Re: Is the Everdrive safe to use on the NES/Famicom?

Post by aquasnake »

In fact, only the CMOS level is rail to rail.

The high level of TTL is approximately 0.7VCC (5V voltage corresponds to an output of about 3.5V, while the high level decision is 2.5V), because TTL has strong suction current (corresponding to L level) and weak pull-out current (corresponding to H level).

The above characteristics of TTL make 5V TTL compatible with 3.3V CMOS, and it can work normally without any current limiting resistor or level shifter.

However, usually not all 5V levels in a system are TTL, which is worth noting. If it is other, such as directly connecting 5V as a fixed pull-up address line, there will be problems (due to the presence of a clamp diode inside the 3.3V input IO, which can tolerate up to 4V levels), of course not all, Some new processes have already removed clamping diodes internally (which is the internal structure of the so-called 5V tolerance input and 3.3V power supply device, which is actually so simple. The 5V tolerance is not because it adds something, but only it subtracts something).

If it is a TTL device with an open collector, its output level can be matched with different IO levels in the subsequent stage. It should be noted that the TTL process is much safer for device IO bus connection, while CMOS devices require stricter level consistency
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aquasnake
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Re: Is the Everdrive safe to use on the NES/Famicom?

Post by aquasnake »

In order to prevent ESD, early processes typically integrated a Schottky diode inside the IO to protect it and ensure its maximum withstand voltage not exceeding vcc+0.7v

The integration of the new process is not Schottky diodes, but TVS, which is two reverse series connected to form a group. TVS also protects IO and breaks through the input limit that can only tolerant up to 0.7v+VCC

My experience with cartridge manufacturing is that early and modern devices have better voltage tolerance ranges, while semiconductor processes in the medium term (approximately 1995-2005) typically have voltage matching issues
lidnariq
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Re: Is the Everdrive safe to use on the NES/Famicom?

Post by lidnariq »

The NES is an NMOS device, and operates on NMOS voltages. It's neither the rail-to-rail of CMOS, nor is it the current-mode logic of TTL. Voltage-wise, it's somewhere in-between. Current-wise, it's also somewhere in-between.
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aquasnake
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Re: Is the Everdrive safe to use on the NES/Famicom?

Post by aquasnake »

NMOS is more similar to the TTL structure, which is also a structure of 1 transistor+1 pull-up resistor (pull-up resistor optional, if not integrated, it is the OD output), but the difference is that the low level output of NMOS is closer to 0V

CMOS is a pair of transistor structures (PMOS+NMOS combination)

TTL and NMOS only have a low level driving force. At high levels, ttl and nmos are in the cut-off state, and the voltage follows the pull-up resistor. CMOS has both low-level and high-level driving force, which is equivalent to vdd-0.3V at a high level
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