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Thread: SaRuMan - 64k static RAM for DRAM replacement board

  1. #1
    eslapion's Avatar
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    Default SaRuMan - 64k static RAM for DRAM replacement board

    A replacement board for the 2 DRAM chips on C64 and C64c boards 250466 and 250469 is available for pre-order.

    This little board replaces the two 64k x 4 bits DRAM ICs with a single static RAM IC. Accordingly it consumes only a trickle amount of power, about 15mA. It also acts as a VSP bug fixer.

    The product's name is SaRuMan-64 and it costs 18$US or 15 Euros.

    Shipping cost is the same as with PLAnkton; shipping a small packet (up to 12 units) to the US is 8$. Shipping cost for Europe, Australia and South America is 10$US or 8 Euros.
    Get a 10% discount on up to 3 PLAnktons if you order them at the same time.

    The product is strictly shipped with antistatic protective packaging. It is covered by a 90 days money back guarantee and a 3 year replacement guarantee afterwards.


    This board replaces the 2 DRAM ICs on boards 250466 and 250469 with a single static RAM IC.
    Complete assembled SaRuMan 64 macro with HDR.
    Assembled product.

    NOW SHIPPING!
    Last edited by eslapion; 27th September 2019 at 10:39. Reason: Now shipping!

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    Looks quite similar to my design. I decided to go with easier to solder IC cases for DIY kits.
    http://www.amibay.com/showthread.php...6-SRAM-for-C64

    Last edited by plazma; 29th June 2019 at 21:31.

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    Quote Originally Posted by plazma View Post
    Looks quite similar to my design. I decided to go with easier to solder IC cases for DIY kits.
    http://www.amibay.com/showthread.php...6-SRAM-for-C64
    I had already announced I was going to release this board here (see post #8 ): http://www.amibay.com/showthread.php...-64k-expansion

    Posted June 27th. I could not predict somebody would come up with a product which is functionally the same 2 days later. I also announced on June 27 the price would be 18$US.
    Last edited by eslapion; 29th June 2019 at 22:43.

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    I'm not accusing of copying. That is a logical form of a PCB if you want to minimize the size.
    One big point of using these is the fix for the VSP bug. One of my units now pass the VSP LAB test.

    - - - Updated - - -

    Did you route the address and data lines to their dedicated pins?
    I activated pin swap for latch inputs, SRAM address and SRAM data. This allowed me to mix the signals and make a cleaner layout.

    You can freely mix the address lines together and data lines together and it works the same

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    eslapion's Avatar
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    Quote Originally Posted by plazma View Post
    One big point of using these is the fix for the VSP bug. One of my units now pass the VSP LAB test.

    - - - Updated - - -

    Did you route the address and data lines to their dedicated pins?
    I activated pin swap for latch inputs, SRAM address and SRAM data. This allowed me to mix the signals and make a cleaner layout.

    You can freely mix the address lines together and data lines together and it works the same
    I see the fix to the VSP bug as a bonus side effect. DRAM is getting difficult to get (although supposedly Abra Electronics has thousands of units in stock) and consumes lots of power.


    I did not mix the address lines and data lines because this board can be used in other products where you can effectively replace a portion of RAM with an EPROM. Considering it is a very tedious exercice to rearrange data in a binary file to compensate for mixed data and address lines, I left them in the correct order. This specific version of SaRuMan (there are 3) does not need pins 1 and 18 for the DRAM IC on the left and only pin 18 for the one on the right because all 4 of them are ground connections and very difficult to desolder.


    The design for SaRuMan uses TSSOP package for all ICs so and no ICs are above DIP pin contacts which allows it to be installed UNDER the C64/64c mainboard if so desired. This, of course, requires removing the metal shield but in my case, that's no problem as I have removed them all and used nickel paint inside the case as shielding instead.


    Here is the schematic:
    Click image for larger version. 

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    Last edited by eslapion; 29th June 2019 at 23:06.

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    Almost the same
    Click image for larger version. 

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    Attached Thumbnails Attached Thumbnails lzMEArB.jpg  
    Last edited by plazma; 12th July 2019 at 09:13.

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    I tried to post changes to my previous post and the forum software systematically erases them.

    ... finally got it...

    Added:
    The design for SaRuMan uses TSSOP package for all ICs so and no ICs are above DIP pin contacts which allows it to be installed UNDER the C64/64c mainboard if so desired. This, of course, requires removing the metal shield but in my case, that's no problem as I have removed them all and used nickel paint inside the case as shielding instead.
    Last edited by eslapion; 29th June 2019 at 23:08.

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    SaRuMan-64 is now shipping!

    Get a 10% discount on up to 3 PLAnktons if you order them at the same time.

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    Just got a new batch of 12 boards!

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