64 kB Expansion RAM cartridge board

MSX 64 kB Memory expansion circuit board, assembled and tested.

  •  This product
  •  Packaging (front)
  •  Packaging (back)
  •  Fits Konami-style cartridge shells (not included)
  •  Example use with Sony HB-10


This is a MSX 64 kB Memory expansion circuit board, assembled and tested.

  • 64kB RAM (fills one slot completely with RAM)
  • PCB: 65.5mm x 43mm, 30° bevel, 2U" immersion gold.
  • Cartridge shell: Not included. Designed for Konami-style cartridges.

Use this product to upgrade an MSX 1 computer with less than 64 kB of RAM to 64 kB.

Example use: The Japanese Sony HB-10, which only comes with 16 kB, can be upgraded to 64 kB with this board.


Unlike most of our items, which ship from Canada, this item is built, sold and shipped from Japan.

Due to Covid-19, only surface shipments are available from Japan to the United States and a few other countries. If you are located in one of those countries, it will be shown on the shopping cart page after you select the destination country. You can still order if you accept to use surface (boat) shipping which takes over 2 months.

We are terribly sorry for the inconvenience, this situation is certainly not something we expected... We hope things return to normal soon...

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In stock : Ships within 5 business days unless noted otherwise (out of stock, pre-order, etc).
DescriptionMSX 64KB Expansion memory cartridge board

We ship within 5 days (excluding week-ends and holidays) after payment.

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Q: BASIC only shows 28815 bytes (up from 12431 bytes or so) when I just added 64 kB of RAM!? Is something wrong?
A: No, this is perfectly normal. The CPU can only access 64 kB or memory (ROM or RAM), and 32 kB are occupied by the BIOS and BASIC ROM. BASIC uses a bit of the remaining 32768 bytes of RAM so in the end only 28815 bytes are free for the user.

Q: If BASIC can only use 32kB of RAM, what's the point of a 64kB RAM expansion?
A: This is mostly a limitation of the BASIC environment, where the BASIC and BIOS ROMs occupy pages 0 and 1. Once loaded (or while loading) games or software may arrange to have a different slot (such as the slot where this expansion was inserted) accessed through page 0 and 1 and therefore use more RAM.