Hi all,
I'm posting this in a seperate thread as it might be of wider interest.
As part of Beeb816, we use a 55ns 5V 512Kx8 SRAM in in DIP 32 package. We wanted to try out a faster 10ns part, but these are only available in surface mount (SOJ and TSOPP) packages. Before respinning the whole board, we though we would try an adapter shim.
The design files are in github:
https://github.com/hoglet67/SRAMAdapter ... ster/kicadThere is a two layer version:
Attachment:
ram_adapter_2layer.png [ 40.84 KiB | Viewed 899 times ]
And a four layer version:
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ram_adapter_4layer.png [ 38.58 KiB | Viewed 899 times ]
The SRAM is in an SOJ-36 package, which just fits between the DIP pins:
Attachment:
ram_adapter_4layer_3d1.png [ 95 KiB | Viewed 899 times ]
The decoupling capacitors are hidden underneath:
Attachment:
ram_adapter_4layer_3d2.png [ 50.09 KiB | Viewed 899 times ]
We ended up going with the 4-layer verstion, which cost just $5.00 for 10 boards from JLCPCB.
This is the first board off the production line, fitted with an a 10ns ISSI IS61C5128AL-10KLI part:
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IMG_2118.JPG [ 340.1 KiB | Viewed 899 times ]
And fitted in Beeb816:
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IMG_2131.JPG [ 483.96 KiB | Viewed 899 times ]
With this, Beeb816 runs stably at 20MHz (previously the limit was about 14MHz):
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capture0.png [ 2.23 KiB | Viewed 899 times ]
I've built three of these, for the three prototype Beeb816 boards.
Attachment:
IMG_2122.JPG [ 477.31 KiB | Viewed 899 times ]
Feel free to make use of this work if you have need for such a thing.
Dave
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