RAM chip

MVS RAM chips often fry due to overvoltage from a badly adjusted or failing cab power supply. It appears that the most common failure mode is the inability to write new data, resulting in errors during system self-test at the beginning of address ranges.

NeoGeo use multiples SRAM (Static RAM) types:
 * Work, Backup and lower Video RAM chips are 256k SRAM (5 volt, JEDEC pin compatible, 32K x 8bit) and only differ by speed. They have "256" or "257" in their markings
 * Fast Video RAM (VRAM $8000~$87FF) chips are embedded into a Neo-GRC chip or 16k SRAM (5 volt, 24pin DIP, 2K x 8bit, 35ns or faster), however some MVS and AES allow the use of a 28pin SRAM by the use of a jumper.
 * Sound RAM chips are 16k SRAM (5 volt, 24pin DIP, 2K x 8bit, 150ns or faster) - fast Video RAM chip can be used as a replacement as they are faster (35ns).
 * Palette RAM chips are 64k SRAM (5 volt, JEDEC pin compatible, 8K x 8bit, 120ns or faster)

See memory speed for details about speed grades.

Work, Backup, Video

 * CXK58256MM-12
 * KM62256CLG-7
 * W24258S-70LE
 * CXK58257AM-12LX
 * any "43256", "62256", CXK58257

Fast Video

 * CXK5814P-35L
 * CXK5863P-35L (only on boards that allow the use by changing the jumper)
 * any CXK5814, CYC128A, 6116

Palette

 * CXK5864BSP-10L
 * LH5168N-80L
 * XLJ6265AF-10SL
 * BR6265BF-10SL

Sound

 * BR6116-100
 * BR6216B-10LL
 * BR6216A-10LL
 * any CXK5814, CYC128A, 6116

Replacement
For Work, Backup and Video RAM look for 256kbit SRAM, 5 volt, JEDEC pin compatible, 32K x 8bit, 120ns or faster in 28 pin SOIC package (not SOJ). Cypress, ISSI, UMC and Lyontek still make them and most today are 45ns, so any will do. This includes 62256, 43256, cxk58257, and others.

For fast Video RAM look for 16kbit SRAM, 5 volt, JEDEC pin compatible, 2K x 8bit, 35ns or faster in 24pin DIP package.

For Sound RAM look for 16kbit SRAM, 5 volt, JEDEC pin compatible, 2K x 8bit, 150ns or faster in 24pin DIP package.

This includes the CXK5814, CYC128A, and 6116 ICs, provided they are fast enough.

For Palette RAM chips The can be replaced by 64k RAM chips off of old 386/486 motherboards (fast cache). This includes the CXK5864BSP-10L 28 pin DIP and LH5168N-80L 28 pin SOIC

MV-1

 * Work: CXK58256MM-12, G3 & H3
 * Backup: CXK58256MM-12, H5 & H6
 * Video: CXK58256MM-12, G4 & H4
 * fast Video: CXK5814P-35L, C5 & D5
 * Palette: CXK5864BSP-10L, H9 & H10
 * Sound: BR6116-100, H1

MV-1A

 * Work: KM62256CLG-7, RAM1 & RAM2
 * Backup: KM62256CLG-7, RAM3 & RAM4
 * Video: KM62256CLG-7, RAM5 & RAM6
 * fast Video: none
 * Palette: LH5168N-80L, BR6265BF-10SL, RAM7 & RAM8
 * Sound: BR6216B-10LL, RAM9

MV-1B

 * Work: KM62256CLG-7, RAM1 & RAM2
 * Backup: KM62256CLG-7, RAM3 & RAM4
 * Video: KM62256CLG-7, RAM5 & RAM6
 * fast Video: none
 * Palette: none
 * Sound: BR6216B-10LL, RAM7

MV-1C

 * Work: W24258S-70LE, RAM1 & RAM3
 * Backup: W24258S-70LE, RAM2 & RAM4
 * Video: W24258S-70LE, RAM5 & RAM6
 * fast Video: none
 * Palette: none
 * Sound: none

MV1FS

 * Work: CXK58257AM-12LX, H4 & H5
 * Backup: CXK58257AM-12LX, H6 & H7
 * Video: CXK58257AM-12LX, B4 & B5
 * fast Video: CXK5814P-35L, C6 & D6
 * Palette: CXK5864BSP-10, H8 & H8
 * Sound: BR6116-10, K3

MV1FZ & MV1FZS

 * Work: KM62256CLG-7, RAM1 & RAM2
 * Backup: KM62256CLG-7, RAM3 & RAM4
 * Video: KM62256CLG-7, RAM5 & RAM6
 * fast Video: CXK5814P-35L, RAM7 &RAM8
 * Palette: XLJ6265AF-10SL, RAM9 & RAM10
 * Sound: BR6216B-10LL, RAM11

MV2FS

 * Work: LH52B256N-70LL, D3 & D4
 * Backup: LH52B256N-70LL, G1 & G2
 * Video: LH52B256N-70LL, C7 & C8
 * fast Video: CXK5814P-35L, C9 & D9
 * Palette: CXK5864BSP-10L, B8 & B8
 * Sound: BR6216B-10LL, K11

MV2-01

 * Work: LH52B256N-70LL, E5 & E6
 * Backup: LH52B256N-70LL, H3 & H4
 * Video: LH52B256N-70LL, F13 & G13
 * fast Video: CXK5814P-35L, F12 & G12
 * Palette: CXK5864BSP-10L, B9 & C9
 * Sound: BR6216B-10LL, BR6216A-10LL, K13

MV-4F

 * Work: CXK58256MM-12L, G9 & H9
 * Backup: CXK58256MM-12L, D9 & E9
 * Video: CXK58256MM-12L, K9 & L9
 * fast Video: CXK5814P-35L, L11 & M11
 * Palette: CXK5864BSP-10L, F4 & H4
 * Sound: BR6216B-10LL, L1

MV-6

 * Work: H9 (lower) & J9 (upper)
 * Backup: E9 (upper) & F9 (lower)
 * Video: L9 & K9
 * fast Video: CXK5814P-35L, M11 & N11
 * Palette: CXK5864BSP-10L, G4 & H4
 * Sound: BR6116-100, M1