RetroUSB AVS vs. Analogue Nt mini - Comparison of the Enthusiast FPGA NES Clones

Until now, any kind of accurate Nintendo NES or Famicom console had to use Nintendo's CPU and/or PPU chips, whether that console was manufactured by Nintendo, Sharp or anyone else.  While the idea of implementing a NES on an FPGA was an idea with a long history, only this year are products finally making it to market.  Here I am going to compare the features of the two announced FPGA NES implementations, the RetroUSB AVS and the Analogue Interactive Nt mini.

Console	AVS	Nt mini
Producer	RetroUSB	Analogue, LLC
Hardware Designer	Brian Parker “bunnyboy”	Kevin Horton “kevtris”
FPGA Type	Xilnix Spartan 6 XC6SLX9	Altera Cyclone V
Included	HDMI, USB Cable (mini-to-standard), Power Supply	HDMI, USB, 8Bitdo NES 30 Wireless Controller, Retro Receiver, Power Supply
Outputs	HDMI, USB	HDMI, Analog Video, RCA Stereo
Inputs	4 x NES Controller Ports, 1 x Famicom Expansion Port	4 x NES Controller Ports, 1 x Famicom Expansion Port, Microphone Input
Upgrade	USB Port	SD Card Slot
Resolution Support	720p	480p, 720p, 1080p (HDMI) 240p (analog sources only)
Video Display Support	HDMI	Composite, S-Video, Component, RGB, HDMI
Buttons	Separate Power & Reset	Combined Power & Reset
Unique Special Features	NA Scoreboard, Built-in Game Genie, Turbo-in-Software	Scalers, Famicom Expansion Audio Generation, Audio Visualizer, Famicom Microphone, NES Zapper/Famicom Gun Support (Analog video only), R.O.B/Family Robot Support (Analog video only)
Price	$185.00	$449.00
Availability	September, 2016	January, 2017

RetroUSB AVS

Brian Parker is best-known for running the retroUSB store.  He released the NES PowerPak, the first commercially available NES Flash Cart, in 2007.  Since then he has released homebrew and reproduction cartridges, the SNES PowerPak and even an adapter to play Gameboy games on the NES.  His AVS is an implementation of the NES on an FPGA and will be shipping to the pre-orderers in September of 2016.

Analogue Nt Mini

Kevin Horton created an accurate FPGA version of the NES in 2005.  He made one of the first homebrew games for the Colecovision, kevtris, and has documented most of the mapper hardware for the Atari 2600 and much of the NES.  He has made accurate FPGA cores for just about every 8-bit system ever made.  He has released his Hi-Def NES mod as an upgrade kit for NESs and AV Famicoms and his mod is incorporated into the HDMI version of the Analogue Nt.  

Both men have proven that they can design an accurate FPGA implementation of the 8-bit Nintendo hardware.  These consoles are as far from the cheap, inaccurate NES-on-a-Clone chip consoles as you can get.  

Analogue, LLC has previously made wooden consoled Neo Geo MVS systems.  For their Nt, they harvested Nintendo-made CPUs and PPUs from cosmetically challenged Famicoms and made a PCB around them.  For the Nt mini, they are using a board designed around the FPGA with no used Nintendo parts, just like the AVS.  Neither console should go out of stock because the producer relied on increasingly scarce Nintendo-made hardware chips.  (They may go out of stock because the FPGA used is discontinued.)  Analogue already has demo youtube videos online for the Nt Mini.  The Nt Mini has been received by reviewers and purchasers alike.  

Interestingly, there is a little of Nintendo's manufacturing in each product.  For the AVS, the Power and Reset buttons come from a cache of new old stock Power and Reset button assembly for the NES Front Loader.  The Nt mini's Power/Reset Button is a red button taken from an NES Controller.  

Upgrades to the AVS are done by plugging the console into a computer via the USB port.  Upgrades to the Nt mini are done by downloading the firmware to an SD card and inserting the SD card into a slot on the Nt mini.

Common to both consoles is support for extra sprites and support for 48KHz digital audio output.  The AVS needs a firmware update to support 48KHz.  

The original Analogue Nt's first run was not compatible with the EverDrive N8 until both devices received a firmware update.  The second run still has unresolved compatibility issues with the EverDrive.  Analogue has stated that the Nt mini will be compatible with both types of EverDrive (NES and Famicom).  Both the AVS and the Nt mini are compatible with the NES PowerPak and EverDrive N8.

Unlike genuine hardware, the AVS and the Nt mini will run NTSC and PAL cartridges and games properly and at their proper speeds.  Some PAL games (like Elite) will refuse to work properly on an NTSC-only system and NTSC games run too slowly in a PAL machine.  A Famicom Disk System's RAM Adapter will fit in both systems.  I believe that the Datach Joint ROM System's cartridge adapter, another bulky adapter that sits on top of the Famicom, will fit in both systems as well.  

The Nt mini goes further than the AVS by allowing for any NES peripheral to work with the system.  The Zapper and R.O.B. (and their Famicom equivalents) only work with a standard definition 15KHz CRT TV.  By providing support for analog video output, the Nt mini enables support for these devices.  The RGB can be set to separate sync, composite/combined sync and sync on green.  Analogue suggests using Monoprice VGA to BNC or Component cables for analog connections. There are also VGA to SCART cables available online from various sellers.  The VGA to Component cable will also work for composite video (the red plug), but you will need something like this : https://console5.com/store/6-foot-1-8m-gold-plated-s-video-s-vhs-to-y-c-luma-chroma-adapter-cable.html and a pair of gender changers for S-Video unless you want to roll your own cable.  Analogue provides the pinouts in its Nt Mini User Manual.

The Nt mini, like the Nt before it, also supports the Famicom microphone for those Famicom games which use it by using a separate microphone.  Even though the AVS only supports 720p and HDMI, you can still use it on a CRT with a converter.  With the converter, you can use the Famicom 3-D System Glasses correctly, according to retrorgb.com. Retrorgb also confirmed that it won't work with a Zapper or R.O.B. even with a converter.

Bunnyboy chose 720p as his resolution because his FPGA did not have the logic elements to support 1080p.  A NES outputs 240 scanlines and the 720p resolution gives an even multiplier of 3.  1080p gives an even multiplier of 4 with top and bottom borders or uneven multiplier of 4.5x, which means that half the scanlines are repeated four times and half the scanlines are repeated five times.  

Unlike the AVS, Nt or the High-Def NES mod, the Nt mini will support a 5x vertical multiplier, which will crop graphics vertically on the top and bottom by 12 pixels on a 1080p screen.  In other words, you will see a centered 256x216 image scaled to 1280x1080.  This will eliminate the top and bottom borders and ensure that every scanline is scaled to the same width.  However, at this resolution, the pixels still have a square 1:1 pixel aspect ratio, whereas on a true NES through its video output, they have an 8:7 PAR.  You can use the horizontal stretching capabilities of the Nt mini to get to 1536x1080, or a 6:5 PAR.  This ensures that every horizontal pixel is of the same width as well as height and should eliminate any ugly shimmering artifacts from games like Contra which show them when the screen is scaled with non-even pixels.  6:5 means that every pixel is 1.2x wider than taller, which is very close to the ideal 8:7 ratio, which gives pixels that are 1.14 wider than taller.  The AVS can evenly scale to 1024x720, which gives a PAR of 4:3, or pixels that are 1.33 wider than taller.

Most TVs back in the day also cropped graphics, many much more than this.  In fact, when Nintendo was first designing its games, it considered the "safe" area of a screen to be the centered 224x192 pixels within the 256x240 frame.  Other companies were comfortable with using the pixels nearer the edges of the visible screen like Konami with Castlevania.  Still others like Capcom in Bionic Commando and Technos in Double Dragon II were happy to use that portion of the screen that was supposed to be hidden by the overscan to hide graphical garbage.  

The AVS has three unique features of note.  First is cheat code support for codes of various formats, including Game Genie, Pro Action Replay, Pro Action Rocky and Raw codes.  The console has a database of codes built in for games it recognizes.  Second is the turbo button settings.  This is a menu that lets you adjust the turbo button sensitivity for the A and B buttons separately.

The third feature is support for the NA Scoreboard.  This will allow you to send your high scores (in games supporting scoring) for recognized games to a server run by NintendoAge.com.  The game's ROM must match the database and the console will not allow cheat codes to be used with the feature for obvious reasons.  It will work with both real cartridges and the appropriate unhacked ROMs run from a flash cart.  

The Nt mini has all the features from the High-Def NES Mod, pure digital implementations of the Famicom Expansion Audio chips, filters and scalers, multiple palettes and the visualizers.  Both the AVS and the Mini have options to stretch and crop the screen, although the Mini offers more settings.  The AVS does not implement Famicom expansion audio, it requires the original cartridges or flash carts to generate the sound and runs it through an ADC.  

The Nt mini essentially combines the outputs of the RGB Analogue Nt and the HDMI Analogue Nt.  Analogue had indicated that you could use both analog and digital outputs on the Nt, but hardware conflicts between the NESRGB and High-Def NES mods made that almost impossible.  With the FPGA design, all outputs are now possible.  If you wanted to, you could even connect to an RF only TV with an Composite to RF adapter box which used to be sold by Radio Shack.  

The AVS's menu is accessible on bootup or by pressing reset.  You can set the console to go directly to the game instead of the menu.  The Nt mini's menu will be overlaid on the game screen and entered by a button combo.  Both consoles can be reset remotely.  

Both consoles have four controller ports and support the NES and Famicom 4-player games.  Both have a Famicom Expansion Port on the back for Famicom peripherals like the Family BASIC Keyboard or the Famicom Arkanoid controller.  While the Nt mini comes with an 8Bitdo Wireless NES 30 Controller, this controller can be used in any system with the appropriate controller port, including the AVS.  You need the Retro Receiver, one of which comes with the Nt mini.  As far as latency with these controllers go, they have been getting solid reviews on that extremely important issue.

The AVS has been in the hands of reviewers and the FPGA implementation is very accurate.  One youtube user, who goes by the name of retroMog, has made videos showing off a prototype version of the AVS.  This prototype is not upgradeable and suffers from a bug in the noise channel.  This can be heard in Contra : https://www.youtube.com/watch?v=B1DpyU5qphI  The released version of the AVS does not suffer from this problem, as shown here : https://www.youtube.com/watch?v=kECeD0wqh90  An early problem reported by a user or two is that the audio sometimes dropped out on two of his TVs, but that should be fixed with the 48KHz firmware.  A few minor incompatibilities with games should be solved with the 1.20 beta firmware.

The AVS is intended to invoke the styling of the front loader.  NES cartridges load horizontally and Famicom cartridges load vertically.  The plastic has a two-tone gray and a black stripe like the front loader.  The Nt mini, like the Nt before it, is made of an aluminum top and a clear polycarbonate base.  Its design inspiration clearly comes from Apple Inc.  The Nt mini and the Nt are pure top loaders.  The Nt mini intends to avoid the issues of scratched cartridges caused by the Nt with wider slots and beveled edges.

The High Def NES Mod has a problem with an inordinate amount of speckling with some games and some consoles, but by using an FPGA in the Nt mini instead of a PPU, this should not be a problem.  The accuracy of FDS expansion audio leaves something to be desired in the Nt mini until kevtris finds out more about how the FDS expansion audio works at the hardware level.  The Nt mini has an option to route cartridge-generated expansion audio to the analog outputs or through an ADC.  

Latency is an issue with both devices, but mainly because of the nature of the display devices they connect to.  The Nt mini may be less susceptible to latency because it supports 1080p, requiring no upscaling by many TVs.  The AVS only supports 720p and true 720p TVs are rare.  Of course, the Nt mini's analog output will not have this issue.  A 4K TV may treat both signally equally when it comes to upscaling because a 2x scale for 1080 and a 3x scale for 720 gets you to 2160.  Bunnyboy has tested his AVS on a 720p TV and two 1080p TVs and was able to get a latency of approximately 1.5 frames compared to a CRT.  This is excellent and should be acceptable for most people.  The Framemeister is in the same latency range.

The Analogue Nt mini comes with one 8bitdo NES30 wireless controller.  This controller is shaped like a NES and uses a bluetooth Retro Receiver to connect to the console.  It can act as a bluetooth peripheral for any device that supports bluetooth gamepads.  The NES30 adds minimal latency and does not require a strict line of sight like a cheap infrared wireless gamepad.  The Retro Receiver is compatible with other bluetooth controllers like a Wiimote and a PS3 or PS4 controller.

Kevtris offers "jailbreak" firmware for the Nt Mini that adds flash cart functionality for ROMs on an SD card.  It is essentially as if a PowerPak or EverDrive was built into the system.  The firmware supports a ton of mappers and will even recognize the iNES 2.0 submappers defined by Kevtris.  He will also offer his FPGA cores for other consoles like the Atari 2600, Colecovision and Sega Master System on a regular basis to all the Analogue Nt Mini to function like one of those machines.  Analogue will not consider a jailbroken Nt mini to violate its warranty.

Both the AVS and the Nt mini are fine products and reasonable price points.  The AVS is intended to provide the core NES/Famicom experience.  The Nt mini is essentially the whole kitchen sink.