Everdrive N8

The Everdrive N8 is a flash cartridge made by Krikzz. It uses an FPGA to emulate a wide variety of mappers, allowing the user to store a large collection of ROMs on a single SD card and run them on an NES or Famicom.

In addition to NES ROMs, the Everdrive N8 is able to play FDS disk images.

Famicom expansion audio is supported, and on the NES version is output on the EXP 6 expansion pin on the cartridge connector as used by the PowerPak. A simple modification to the NES allows the expansion audio to be mixed with its output.

Specifications:

• PRG size: 512 KB
• CHR size: 512 KB

NES product: http://shop.krikzz.com/EverDrive-N8-NES-EDN8NES.htm

Famicom product: http://shop.krikzz.com/EverDrive-N8-Famicom-EDN8FAM.htm

See also: PowerPak - A similar product by RetroUSB

Mapper compatibilty

The OS update v11.1 in September, 2014 supports the following mappers:

000	001	002	003	004	005	---	007	---	009	010	011	012	013	---	015
016	---	018	019	---	021	022	023	024	025	026	---	028	---	---	---
032	033	034	---	036	---	038	---	040	041	042	---	---	---	---	047
048	---	---	---	---	---	---	---	---	057	058	---	---	061	---	---
064	065	066	067	068	069	070	071	072	073	074	075	076	077	078	079
080	---	082	---	---	---	086	087	088	089	---	091	092	093	094	095
096	097	---	099	---	101	---	---	---	---	---	107	---	---	---	---
112	113	---	115	---	---	118	119	---	---	---	---	---	---	---	---
---	---	---	---	---	133	---	---	---	---	---	---	140	---	---	---
---	---	---	---	---	---	---	151	152	---	154	---	---	---	158	---
---	---	---	---	---	---	---	---	---	---	---	---	---	---	---	---
---	---	178	---	180	---	182	---	184	185	---	---	188	189	---	191
---	193	---	---	---	---	---	---	200	201	---	203	---	205	206	207
---	---	---	---	212	---	---	---	---	---	---	219	220	---	---	---
---	---	---	---	---	---	---	231	232	---	---	---	---	---	---	---
240	241	242	243	---	245	246	---	---	---	---	---	---	---	---	---

Known problems:

• Mapper 5 (MMC5) does not support expansion audio.
• Mapper 69 (FME-7) does not support expansion audio.

Software development limitations

Aside from mapper incompatibility, there are minor differences between running NES programs on the Everdrive versus a traditional single-game cartridge.

• The Everdrive does not accurately simulate power-on state. Because power-on always boots the Everdrive menu, RAM and various registers will be initialized to a consistent state before any NES ROM is chosen to run. (Reset state, however, is not affected by this problem.)
• Open bus behavior may be different in several memory regions that are used by the Everdrive, but would not be connected on a regular cartridge. (forum post)
• The Everdrive is incompatible with an NES that has the CopyNES modification installed, due to a bus conflict with its boot code.

Everdrive development resources

• Software tools and example mapper source code: http://krikzz.com/pub/support/index.php?dir=everdrive-n8/development