Category:RAM Expansions
This page was last modified 09:35, 22 May 2022 by Mars2000you. Based on work by Gdx and Eugeny Brychkov and others.


Important points to take into account for buying a RAM expansion

Before buying a memory expansion, you need to pay attention to several points.

  • MSX1 system can by default only see up to 64kB. It is called the main RAM and can only be located in the following areas. RAM in different areas or in other slots will only be usable for specific applications.
    • 8kB MSX1: E000h-FFFFh
    • 16kB MSX1: C000h-FFFFh
    • 32kB MSX1: 8000h-FFFFh
    • 64kB MSX1: 0000h-FFFFh
  • a memory mapper expansion cartridge can be added to a MSX1, but the MSX itself will not be able to initialise it. So either the memory mapper must be able to self-initialise or you must manually initialise it each time.
  • All MSX2s have at least 64kB RAM. If they have exactly 64kB RAM they may or may not have a memory mapper, if they have more then 64kB they will have a memory mapper. You can add an expansion without memory mapper but it will only be usable for specific applications. Note that if a memory mapper is added, it will not necessarily be selected at start up. It depends on the slot location of the internal RAM, compared to the slot the expansion is installed in.
  • MSX2+ computers always select the first additional memory mapper at start because the internal RAM is in a secondary slot 3-x. (if you do not place another RAM expansion in a lower slot.)
  • MSX Turbo R always selects its internal RAM.
  • MSX-DOS2 selects the largest memory mapper as main RAM except on a MSX Turbo R.

8kB and 16 kB RAM expansion cartridges

These cartridges were designed to upgrade a MSX1 with 8kB to 16kB or a MSX1 with 16kB to 32kB of memory. On those systems, they will also increase the amount of free memory in BASIC. The 8kB expansion is designed for the Casio PV-7. This computer is an exception, avoid expansions from 16kB to 48kB for it. These are only usable for very specific cases on this computer.

Model Capacity Notes
Addcom ADMSM 301 16kB
Casio KB-7 8kB Casio PV-7 or Sanno SPCmk-II only
Casio OR-208 8kB (16KB) Casio PV-7 or Sanno SPCmk-II only
Casio OR-216 16kB
Daito Micom System Rom Hunter 16kB 32kB cartridge
Daito Micom System Rom Hunter mkII 16kB 256kB MegaRAM cartridge
Fujitsu MB22451 16kB Fujitsu FM-X only
General RJ-102 16kB
Hitachi MP-RA01H 16kB
Mitsubishi ML-16RAM 16kB
National CF-2131 16kB
Philips VU 0031 16kB
Sanyo MRP-16 16kB
Sony HBM-16 16kB
Toshiba HX-M250 16kB

32kB to 64 kB RAM expansion cartridges

These cartridges were mainly designed to upgrade an MSX1 to 64kB. This allows the use of MSX-DOS for example. The 32kB expansions will upgrade a 32kB MSX1 to 64kB. The 48kB expansion will upgrade a MSX1 with 16 or 32kB to 64kB and the 64kB expansion will upgrade any MSX1 with less then 64kB to 64kB.

At first sight an 64kB expansion may seem overkill as either a 32kB or 48kB expansion would be sufficient to upgrade to 64kB. It is however preferable to have all 64kB in the same slot as some software titles blindly assume this to be the case. Having the memory split between different slots can cause incompatibility problems with a few (often European) titles.

The 64kB expansions cannot be used to upgrade main memory of a 64kB MSX to 128kB, as that requires a memory mapper which these cartridges lack.

Model Capacity Notes
Addcom ADMSM 302 32kB
Addcom ADMSM 303 48kB
Casio OR-264 64kB
Neos RM-48 48kB
Pioneer PX-RA32 32kB
Philips VU 0034 64kB
Sanco Memoire Ram 64Ko 64kB
Sanyo MRP-64 64kB
Sharp-Epcom HB-4100 64kB
Sony HBM-64 64kB
Spectravideo SVI-747 64kB
Toshiba HX-M251 64kB
Walther Miller WM 0587 64kB Dubious manufacturer, avoid!
Yamaha SRE-01 32kB Only for systems with Yamaha 60-pin Expansion slot
Yamaha SRM-01 32kB Only for systems with Yamaha 60-pin Expansion slot
Yamaha URM-01 32kB

The following diagram shows what RAM the system selects as main memory on an MSX1 that has its RAM in slot 0. It is an example for illustrative purposes as that is the case for most MSX1 systems with less than 64kB of RAM. However, the memory can in reality be located in any slot.

MSX RAM Expansion.png

Green areas are RAM regions selected by default when running BASIC. Green and light green areas are RAM selected by default under MSX-DOS1 (system with disk). Yellow areas are ignored by the system. These areas will only be usable for specific applications.

As you can see in the diagram, a 16kB expansions are designed for 16kB MSXs, 32kB expansions are designed for MSXs with 32kB, 48kB expansions are designed for MSXs with 16kB or 32kB. As for 64kB RAM expansions, they are suitable for all MSX1s.

While having memory split between slots is supported in the MSX specification (and some MSX systems even have the internal memory split over two slots), when the main memory is located in different slots it is known to cause problems with software that blindly assumes that all the RAM will be in a single slot. To avoid this problem choose an expansion with memory mapper that initialise itself at start and use BMMS before executing your software.

External memory mapper cartridges in machines with T9769 MSX-Engine chip

This chip is usually installed in the Turbo R machines, and, when reading the mapper registers at ports &HFC to &HFF, pulls unused mapper bits to +5V with enough current causing considerable heat and current consumption. Here's the excerpt from the article in the MSX Computer and Club Magazine #65 (page 37, translated from Dutch):

Due to an error in the engine Toshiba T9769, the non-connected data bits are read back as a 1 (+5 Volt) ... In itself this is not bad, the engine S1985 (Sony F700) does this, but with the T9769 the unused data bits are connected low-ohm to the +5 Volt. When a second mapper is used in the system, that is larger than the internal mapper, this second mapper will attempt to pull these data bits down. If the buffer placed in the external mapper is strong enough, this configuration will indeed work. Apparently everything works normally, but at that moment there is a large current, which generates a lot of heat in the T9769 engine.

Memory Mapper expansion cartridges

These expansions are primarily meant for MSX2 and MSX2+ systems. The MSX1 BIOS is not able to initialise them, but you can manually initialise them or some cartridges can self-initialise.

For more information about how a Memory Mapper works, see Memory Mapper.

The MSX1 column indicates that the Memory Mapper is fully MSX1 compatible, which means it is able to initialise its segments to 3, 2, 1, 0 at the system start (hard reset or power cycle) itself.

Model Capacity MSX1 7 MHz Turbo R Notes
8bits4ever MEGA-MAPPER 1, 2 or 4 MB Yes Yes
8bits4ever SD-512 512 kB Yes Yes
ASCII MEM-768 768 kB No Yes
ASCII Nihongo MSX-DOS 2 0, 128 or 256 kB No No
Carnivore2 1 MB Yes Yes
Caro 1024KB Expansion RAM 1 MB Internal upgrade for selected
Yamaha systems (e.g. CX5MII)
Classic PC 16MB Expansion Memory 16 MB No Yes
Digital KC MSX Memory Mapper 2 MB No Yes Yes
Green MSX WBM512 512 kB
GR8NET 1 MB Yes Yes Yes
Hardware Partners TM 512 kB, 1 MB
HSH RE-512 MM 512 kB
Megaminx Memory Upgrade Board 256 kB Internal upgrade for Panasonic
MFP Extended Memory-2048K 2 MB No Yes
MK Public Domain MSX Memory Mapper 1, 2 or 4 MB No
MegaFlashROM SCC+ SD 512 kB Yes Yes Yes
MSX Club Gouda Memory Mapper 1, 2 or 4 MB No Yes Yes
MSX Club Gouda Memory Mapper E.M.S. 1, 2 or 4 MB No Yes Yes
Padial LPE-4FMB-V8SKP 4 MB Yes Yes Yes
Padial LPE-4MB-V4SKP 4 MB Yes Yes Yes
Padial LPE-512KBSRAM-V3 512 kB No Yes Yes
Playsoniq 4 MB No Yes Yes Mapper up to 16M using an extra register (not standard)
Popolon MSX Memory Mapper 1 MB Yes Yes Yes
Popolon Musical Memory Mapper 1 MB Yes Yes Yes
R. & J.Jansen Memory Mapper 256/512 256 kB, 512 kB No No
Sony HBM-512 512 kB No No No
Stichting CODE MCR-025 256 kB Yes Combined with RAM Disk + Printer buffer
Stichting CODE MCR-051 512 kB Yes Combined with RAM Disk + Printer buffer
Stichting CODE MCR-076 768 kB Yes Combined with RAM Disk + Printer buffer
Stichting CODE MCR-102 1 MB Yes Combined with RAM Disk + Printer buffer
Stichting CODE MCR-204 2 MB Yes Combined with RAM Disk + Printer buffer
T.N.S. Addram 4 MB No
Tecnobytes Double RAM 4 MB Yes Yes

Pages in category "RAM Expansions"

The following 70 pages are in this category, out of 70 total.










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