Sunday, March 17, 2019

Mega EverDrive X7 - Almost Everything You'd Want in a Flash Cart

Mega EverDrive X7, courtesy of Amazon.com
 A long time ago, over six years in fact, I purchased my first Krikzz product.  This was the Mega EverDrive (v1), then by far the most capable flash cartridge ever released.  I wrote about it here.  Recently I have had the opportunity to acquire its successor, the Mega EverDrive X7.  Let's revisit the use of flash carts on the Genesis/Mega Drive with the X7.

Features of the Mega EverDrive X7

The Mega EverDrive X7 was originally introduced as the Mega EverDrive v2.  Soon after its release in 2014, Krikzz rebranded it using his "X" series of classifications to distinguish levels of similar products.  The X7 was later followed by the less-featured X5 and X3.  It is priced at $166.00, which is around the same price as the v1.  These days they will come with enclosures, so I had no need to find a cheap Genesis/Mega Drive cartridge to hack up for a donor shell.  Back in the v1 days, I had to order from Ukraine or Germany and it took weeks to arrive.  Now I ordered from EverdriveStore.com on Monday and had it on Friday.

A flash cart's purpose is to load software without needing the original cartridge.  There are legitimate uses for flash carts such as playing scene demos and freely-distributable homebrew software.  As development tools for new software they are invaluable and far, far easier to deal with than burning EPROMs on donor/development boards or finding old copiers that loaded data off PC floppy discs.  However, most people use flash carts to play ROMs of games that have not been placed in the public domain.

The Mega EverDrive is easy to setup.  Just download the latest OS, v3.07 at the time of this blog entry, and copy the MEGA folder contained therein to the root of a FAT32 formatted micro-SD card.  Then copy your ROM directories over and enjoy.  There is a nice user manual which explains the features in good detail, but some features have changed and have been added since 2014, so check the OS readme here to complete the picture of the device's features.  The EverDrive file browser and menu controls are also intuitive : A enters directories or selects menu items, B goes back/up from directories and submenus, and C brings up the EverDrive Main Menu.

The Mega EverDrive X series, like the v1 before them, all copy software from a micro SD card to PSRAM.  This allows software to load far faster than the old, now discontinued EverDrive MD flash carts.  The EverDrive MD copied software from SD card to flash memory, which was a painfully slow erase-then-write process when you wanted to load games larger than 1MB.  The X7 loads games really fast, a 4MB game will load almost instantaneously.  In fact, the UI feels zippier overall compared to by v1.  Some EverDrives have issues with certain brands of SD cards, but I have not had any issues with my X7 so far.  The Mega EverDrive v1 and X7 have a USB port which can be used to load software directly onto the cartridge without requiring an SD card, but its mainly intended for development purposes.

The Sega Genesis/Mega Drive normally supports games from 128KB to 4MB without additional hardware.  It does not use a lot of varied memory mappers like the NES or special chips like the SNES.  Virtually all official games fall within the standard memory layout.  Any game which would fail on a TMSS Genesis/Mega Drive console will work when loaded via the Mega EverDrive.  One official game, Super Street Fighter 2, requires a mapper and the Mega EverDrive supports that mapper.  The renowned OverDrive 2 demo also uses that mapper and runs with the X7  The Mega EverDrive X7 can also support loading software up to 10MB in size if a Sega CD or 32x is not present.  The Ultimate Mortal Kombat 3 Trilogy hack and the Bad Apple (unsplit) demo require this support to be run on original hardware.  The Ultimate Mortal Kombat 3 Trilogy hack is 10MB and can only load on the X7 or the v1.  The Mega EverDrive does not support Virtua Racing's SVP, so you will need an original cartridge (or a 32x) to play that game.

There are about two dozen Sega Genesis/Mega Drive games that do not use the typical SRAM or similar methods to save games, instead they use serial EEPROM.  The X7 supports all forms of EEPROM used by Genesis/Mega Drive games, X24C01, 24C02, 24C08, 24C16, 24C64. These devices store 128 bytes, 256 bytes, 1K, 2K and 8K respectively. The only difference between these games and standard SRAM games is that the X7 requires pressing reset before it will save an EEPROM game's data. The X7 (and X5) will store the data of an SRAM game via its battery backed up memory when you shut the game off. The original Mega EverDrive v1 did not support EEPROM games and did not have a battery to keep game saves when you turned the power off. You had to train yourself to hit the reset button or all your hard work instantly disappeared.

When you start a new game supporting SRAM, the X7 and X5 will copy the contents of SRAM to a file. Then when you play that game again, the X7 and X5 will restore that file automatically to the SRAM before loading the game. This happens very quickly.

Other features new to the Mega EverDrive X7 are a list of recently played games like the sd2snes, start random game and the Toolbox. The Toolbox allows you to diagnose your flash cart to see if any errors occur. It also allows you to reset all settings to default. Most importantly, it allows you to copy the contents of SRAM to the SD card just in case you want to ensure your save game is backed up. Batteries do not last forever. It also lets you copy save files manually to SRAM if you want to experiment. The Options menu allows you to turn the File Sorting Off if you want your ROMs displayed in a particular way.

The Mega Key and the Region Setting work in concert with each other. The Mega Key allows you to change the Region reported to a game, USA, Japan and Europe it allows. By 1992, most games will show some kind of warning screen and fail to continue if you are not using them in the "right" console. The Mega Key should bypass those screens, but that is all it can do. It cannot change your console from NTSC to PAL or vice versa. If your game will not work at NTSC speeds or PAL speeds or shows glitches or runs audio too fast/slow, the Mega Key won't help you. Additionally, if a game has a routine that detects not just the region reported but the parameters of the VDP that it doesn't like, the Mega Key won't help you there.

The In-Game Menu allows for save states. When you load a game, you should be able to bring up the In-Game Menu by holding Down and Start. This will bring you to a menu that allows you to load a save state, save the state or return to the main menu (quitting the game in progress) without having to reach for the reset button on the console. Save states are very useful with games which do not have a battery save or have long passwords. You can also preview save states or start the game at the save state by loading the .gen file, which is very convenient.

The In-Game Menu may not work for all games, support for any particular game is not guaranteed. The save state may crash when loaded. Finally, the music driver for most games is usually run by the Z80 Co-Processor in the Genesis/Mega Drive and the save states only save the state of the main 68000 CPU. It has no access to the Z80's bus. This can result in the music being out of sync or not being played back properly or at all until the music engine writes to the particular audio chip registers. Software emulators have access to the whole system and they can avoid the sync issue.

Reset to Game allows you to press reset and the game should do whatever it does when you press reset with an original cartridge. To get back to the Mega EverDrive's main menu you must power cycle the console. This will allow you to get past a certain point in X-Men which requires you to reset your console to progress. If the Reset to Game option is off, then any press of the reset button will return you to the Mega EverDrtive's main menu.

When the Cheat option has been turned On, you will see Cheats added to the Main Menu. Cheat codes allow for not only Game Genie codes but also "Raw" codes. Raw codes are in the form of memory addresses. The Genesis/Mega Drive has a 24-bit Address Bus and a 16-bit Data Bus, so the codes take the form of a three-byte address value and a two-byte data value, in hexadecimal. The Raw code format was used by the Action Replay but Mega EverDive supports ROM codes, not RAM codes. Cheating is limited to games in size of 4MB or less and the Mega EverDrive will reject codes to memory locations outside the ROM area (essentially codes with addresses in the $400000-$FFFFFF range will be rejected). The EverDrive will reject codes outside of this region.

Entering cheat codes will seem a little cumbersome at first, but if you use a lot of cheats you will come to appreciate the system. To use cheats, you must Select a game, not Select and Load Game. Then you go to the cheats menu and enter your cheats. Alternatively, the Mega EverDrive will allow you to load a .txt text file with Game Genie codes entered in it to save you the trouble of manually entering them in. When you have finally entered your codes, then Select and Load Game and they will be applied to that particular game and no others.

Users of the Sega CD will find the X7 very useful. Some Sega CD games can save their progress either to RAM inside the Sega CD or RAM on a CD RAM cartridge. The X7 and X5 can behave as CD RAM cartridges, eliminating any limits on your Sega CD save games. The Mega EverDrive cna also load a different Sega CD BIOS like a ROM to bypass the Sega CD's region protection. Additionally, the Mega EverDrive supports loading 32x ROMs if you have a 32x inserted into your Genesis/Mega Drive, so owners of that add-on have that small library instantly at their fingertips.

There is a music player built into the Mega EverDrive which can play Genesis/Mega Drive and Master System chiptune music in the GYM anf TFC formats. The X7 cand v1 an also 8-bit/22 KHz .wav files. Just load the file and the music will start playing.

Master System Features

All Mega EverDrives support loading Sega Master System games. It essentially adds most of the functionality of the Power Base Converter to the flash card. The button on top of the Mega EverDrive v1, X5 & X7 functions as a pause button for Master System games and a hard reset button for Genesis games in the X5 and X7. The Genesis/Mega Drive does not support the TMS9928 modes that the Master System did, so SG-1000 games and F-16 Fighting Falcon will never work on a Genesis/Mega Drive. 3-D glasses also will not work due to the lack of a card adapter. Some games will not work properly with Genesis/Mega Drive 3-button or 6-button controllers, here are patches to fix those issues. That thread also has patches for some Genesis games which do not work as pure dumps in the Mega EverDrive. Some European games may not display properly (anything by Codemasters) or work at all (Pit-Fighter) because the Genesis/Mega Drive VDP loses some features from the PAL Master System VDP.

The X7 adds two features which will be appreciated by Master System fans.  The Master System loaded BIOSes, but the Power Base Converter does not.  If you wish to simulate the Master System experience more closely, you can instruct the X7 to load one of three BIOSes.  The instructions are included in the readme accompanying the OS files.  While a BIOS is not generally required to make games work, this may also improve compatibility with a few games.

In addition to loading BIOSes, the X7 also supports the YM2413 FM addon found in the Japanese Master System and which can be added to the Mark III.  The quality of the audio is good and the accuracy is also on par with other available solutions that do not use an original Yamaha YM2413 chip (Nt Mini).  It isn't perfect, After Burner's take off sound effect is noticeably off for example, but for most it will be far superior sounding to the square wave PSG found in the unexpanded Master Systems.  Wonder Boy III: The Dragon’s Trap and Time Soldiers require patches to enable the FM in the Genesis/Mega Drive, find them here.

Recommendations & Conclusion

So is the Mega EverDrive a good purchase?  For an owner of a Flash-based EverDrive MD, yes.  The features are so much more advanced that those old dogs should be retired.  If you have a Mega EverDrive v1, then the extra features of the v2 are not worth the double dip unless you can get a decent price when selling your v1.  If you've never owned a Genesis flashcart before, then the answer is a clear Yes!  In fact, there are no competitors to Krikzz' products for Genesis flashcarts. 
Mega EverDrive v1 - courtesy of SegaRetro,com

However, there is a reason why you should wish to consider the X5 over the X7.  The X7 was developed before the X5.  The Genesis is a console that operates on 5v logic, but the Mega EverDrives use modern chips which operate with 3.3v logic levels.  When chips of different logic levels are interacting with each other, there should be level translator chips in the signal path to translate the logic levels accordingly.  If this is not done, then the higher voltages from the 5v parts and the lower voltages from the 3.3v parts will cause their counterparts to run out of specification. 

When the v1 was designed, Krikzz mitigated the issue by using current limiting resistors on all the address and data lines.  The theory behind current limiting resistors is that instead of the clamping diodes inside the 3.3v chips dissipating the excess voltage from the 5v source as heat, the current limiting resistors do the job externally to the chips.  Heat is the enemy of silicon-based integrated chips.  If those diodes break down, then they could cause a short circuit and a voltage spike that could take the flash cart and even perhaps the console itself to the scrap heap. 

Mega EverDrive X7 PCB - courtesy of krikzz.com

Current limiting resistors limit the most obvious harmful effect, but the ICs are still being over/under volted whenever 1s are being output.  The X7 has 2 logic level translation chips, and these chips can handle 16 a piece.  Between the address and data lines, the cartridges have access to 40 signals alone, nevermind the additional signals used for other cartridge functions read enable, write enable and chip enable.  8 of the data lines and some other signals are still being serviced only by current limiting resistors.  When Krikzz designed the X5 and X3 at a later time, he added a third logic level shifter allowing for 48 signals, which is sufficient to handle all the signals the Mega EverDrive needs. 




EverDrives have not been shown to be console killers.  However, remember that these consoles are over a quarter-century old now and their chips do not age like a fine wine.  A console, like people can die at any time.  A cheap Chinese-made multi-cart that runs the flash off 5v without any protection is far more dangerous.  The proper amount of logic level translators will not add additional stress on the chips compared to original cartridges.  Without them, you may prematurely age your console and shorten its lifespan. 

Mega EverDrive X5 PCB - courtesy of krikzz.com
Let me analogize using flashcarts or multicarts without proper voltage translation to smoking.  Having a cigarette is unlikely to kill you.  Developing a smoking habit isn't likely to cause too much immediate damage but it will cause damage over time.  Using a cheap multi-cart is like smoking menthols, they are perhaps the most dangerous cigarettes because of the extra chemicals to produce the mentholated taste.  The current-limiting resistor approach is like smoking regular cigarettes.  The hybrid approach of the X7 is like vaping, it isn't great but it isn't as harmful as the other methods. 

If you want to be safe, buy the X5.  The X5's biggest deficiency is the loss of save state support and in-game menus.  It is also limited to 7MB ROMs, no you won't be able to run OverDrive 2, BadApple (without a split ROM) or the Ultimate Mortal Kimbat Trilogy hack.  No FM Support, but you can get a Master EverDrive X7 and a Power Base Mini FM for that.  EEPROM games won't work/save properly, but the only two that anyone cares about, Mega Man and Monster World, have SRAM patches. 

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