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: https://krikzz.com/store/home/31-everdrive-n8-nes.html

Famicom product: https://krikzz.com/store/home/32-everdrive-n8-famicom.html

See also: PowerPak - A similar product by RetroUSB

Mapper compatibility

As of the OS update v1.26 in 2021, the Everdrive N8 supports the following mappers: [1]

000	001	002	003	004	005	---	007	---	009	010	011	012	013	---	015
016	---	018	019	---	021	022	023	024	025	026	027	028	---	030	031
032	033	034	035	036	037	038	---	040	041	042	---	044	045	---	047
048	049	050	051	052	---	---	---	056	057	058	---	060	061	---	---
064	065	066	067	068	069	070	071	072	073	074	075	076	077	078	079
080	---	082	---	---	085	086	087	088	089	090	091	092	093	094	095
096	097	---	099	---	101	---	103	---	105	106	107	108	---	---	111
112	113	---	115	---	117	118	119	---	---	---	---	---	---	---	---
---	---	---	---	132	133	---	---	136	137	138	139	140	141	142	143
144	145	146	147	148	149	150	151	152	---	154	---	156	---	158	159
---	---	---	---	164	165	---	---	168	---	---	171	172	173	---	175
176	177	178	---	180	---	182	183	184	185	186	187	188	189	190	191
---	193	---	---	196	197	198	199	200	201	202	203	---	205	206	207
---	---	---	211	212	213	214	---	216	---	---	219	220	221	222	---
---	---	---	227	228	229	---	231	232	---	234	---	---	---	238	---
240	241	242	243	244	245	246	---	248	249	250	---	252	---	---	---

Known problems:

• Mapper 71 only supports the memory controller used by FireHawk, all other Mapper 71 games must be reassigned to Mapper 2 to work correctly.

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/everdrive-n8/original-series/development/