FM Towns:CPU Upgrade for Desktop Models

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Revision as of 02:49, 13 August 2022 by Cyo.the.vile (talk | contribs)
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Basic information

Desktops had a slot to place CPU upgrade cards with some later models requiring the CPU upgrade card to be present as there wasn't a CPU onboard the motherboard.
There was absolutely zero retail software that required anything more powerful than a 486DX2 CPU and the majority of software was designed for the base 386 model in mind.
The white desktops with 4 expansion slots are optimal as some CPU upgrade cards were taller and designed for them.
The white desktops with 3 expansion slots are shorter and thus more limited on CPU upgrade cards.
The 486DX4 cards for the Towns MX/MA type desktops will work in a smaller desktop (EA/ME). However, you won't be able to close the top lid.

Spotting cards in auctions

Sometimes sellers on Yahoo Auctions Japan will have the lid taken off of the computer.
This is a good opportunity to see if a CPU card is present or not.
It will also generally raise the price.

  • MX Model with no CPU card present.

    MX Model with no CPU card present.

  • A CPU Card is present in this Fresh ES. Likely a 486DX2.

    A CPU Card is present in this Fresh ES. Likely a 486DX2.


List of CPU Upgrade cards divided by Desktop type

  • FMT-361
    Official Fujitsu Product. For HR desktops only. 486DX2 @ 40MHZ
  • PK-FM486
    By I-O Data Equipment. For HR desktops only. 486DX2 @ 40MHZ
  • (Unknown Model number)
    By SoftBank Corp. For HR desktops only. 486DX2 @ 40MHZ



  • FMT-3621/3621A
    Official Fujitsu Product. For ME desktops only. 486DX2 @ 50MHz



  • FMT-3623
    Official Fujitsu Product. For MA/MX only. 486DX4 @ 100MHz

  • FMT-3622/3622A
    Official Fujitsu Product. For EA/MA/MF/Fresh only. 486DX2 @ 66MHz
  • ODBT486F
    By Urban Corporation. 486DX2 compatible CPU (5V) support. Should fit most desktops except HG/HR
  • ODBT486Z
    By Urban Corporation. The Holy grail and best card as it supports 486DX4 CPU (3.5V) and can use a 5x86 CPU.
    Often sells for $100-300+ on auction. Fits all desktops except HG/HR.
  • ODBT486
    By Urban Corporation. 486SX/DX/DX2 compatible CPU (5V) support

  • FMT-3651
    Official Fujitsu Product. For HA Pentium only. 60mhz.
  • FMT-3652
    Official Fujitsu Product. For HB/HC Pentium only. 90mhz.



In addition, the Pentium models can accept the following CPU upgrades.

  • PentiumODP(120/133MHz)
    For HB Model only. Overdrive processor.
  • PentiumODP(150MHz)
    For HC Model. Overdrive processor.
  • PentiumODP(166MHz)
    For HC Model. Overdrive processor.
  • MMXPentiumODP(166MHz)
    For HC Model.
  • MMXPentiumODP(180MHz)
    For HC Model.


There are also reports of users putting a K6 CPU inside a Pentium HC model.

Good Information

Hota-san has a very good page explaining some of the CPU upgrade cards.

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