512KB Memory Expansion Module for SHARP PC-1600 by Tom

After my PC-1500 memory module which need some corrections, i’m very proud to present you this incredible 512KB memory module for the PC-1600 built by Tom.
The best thing to do is to let Tom explain it :

At the beginning of 2014 I rediscovered the fascination of the vintage SHARP pocket computers. My very first computer was indeed a PC-1500/CE-150 which I found somewhere deep down in my storage. And it was still working (except the rechargeable battery of course)!

In the 80s, when I was a boy, however the PC-1600/CE-1600P was a dream, but too expensive for me by magnitudes. So I was lucky to buy one from ebay. Since I’m a computer scientist, I was interested to treat that machine like an embedded system using a modern software dev environment and the sdcc/Z80 C-compiler. I succeeded, but soon noticed that the RAM-disk was too small, even on a 32KB+64KB config.

So I searched for custom vintage Tramsoft and Bajic 256KB modules, but couldn’t get one.
That was the point, when I decided to build my own. Luckily I found the homepage of Kai Bader, who kindly offered me one of his breakout boards and I started experimenting with SRAM ICs.
The hard part for me was to decode the PC-1600 vertical bank switch of slot 2, but finally I got my first 256KB RAM module in my hands.

Technical Data (rev 1 – sold out)
* 256KB RAM module with low power SRAM chip
* 32KB can optionally be reserved as a main memory extension, the rest is used as RAM-disk
* No battery buffer

I send one to Kai and he posted it on his website. Allmost immediately I was contacted by Eric – the owner of this great site – who had some clever suggestions for technical improvements and organized a poll at the silicium.org enthusiasts forum for a revision 2 of the board.
Since my first version had a 512KB SRAM chip on board of which “only” 256KB was used, the main improvement was to provide a 2x256KB mode and a 512KB mode.
It was clear soon that the 512KB harware mode was not supported by the PC-1600 INIT-command, but after some fiddling about I managed to write a patch routine that overcomes this problem.
And that was the birth of the first 512KB RAM module for the SHARP PC-1600.

Technical Data (rev 2 – sold out)
* as rev 1 but 3 modes of operation:
– 256KB mode, without need of any additional init software or peeks/pokes
– 2x256KB mode, with two banks 256KB each – to be switched by an additional hardware switch
– 512KB mode, needs an additional custom patch routine to get that mode running
* Battery buffer not included, but a description for mod available.

For more details see

Technical Data (rev 3 – planned)
* as rev 2 but with (better) battery buffer support incorporated

Thanx again Eric for your support and this very informative and entertaining site.

Thank you Tom for this module !
My friends from Silicium and me are happy with our 512KB PC-1600 🙂

>Click to download the full module description <<


8 thoughts on “512KB Memory Expansion Module for SHARP PC-1600 by Tom

    1. Tom

      Hello Barbe, Dainius (or others),
      The Rev3 is (was) out in late 2016 – but I`ve got a few modules left for spare.
      So, if you want one, you can post here – or contact me at silicium.org via PM at my alias ‘spellbound’.
      Best regards

    2. chunming wen

      Hello there:
      I want to buy your product(512KB Memory Expansion Module for SHARP PC-1600) I live in Taiwan. How to buy it?

  1. Dainius

    Any plans to make Rev 3 available this year? I would be interested in acquiring the module for my PC-1600 (I’m using Bajic 32K and 64K modules at the moment).

    And thank you very much for this blog!

  2. HBE

    As you mentioned a “Bajic” expansion board, I wonder if you could help me: I just purchased a PC 1500 on ebay and it came with an expansion board installed that looks exactly like the one shown here :


    I also get close to 28k for MEM .

    From what I can see from the photos posted under that link (front and backside of the board) , this one has
    – an 8KB RAM chip
    – a 32 KB RAM chip
    – and the thing on the front side could be an EPROM. How can I find out what exactly this is?

    Thanks in advance

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