C103175 REV 1 (520 STFM)
Posted: Fri Apr 06, 2018 5:43 pm
- 520_stfm_c103175_rev1.JPG (3.01 MiB) Viewed 7881 times
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C103175 REV 1 (520 STFM)
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(This is an "IMP ST" - all chips are IMP versions. DMA and Shifter in sockets)
Re: C103175 REV 1 (520 STFM)
Posted: Fri Apr 06, 2018 9:42 pm
This looks a lot like my C103414-001 board. It has the same IMP chipset, layout is similar only on your board the memory is through hole. On my board, the memory is also SMT. The pinout of those DRAM’s should be the same as on mine, only the package is different. On my board, we’ve removed the 256kx4 DRAM’s and replaced them with 1Mx4 DRAM’s, we also filled the memory bank next to it with 1Mx4 DRAM’s, so in total 8 DRAM’s on the board. Pin 5 on the DRAM chips is A9, connected them together, joint the two wires, soldered a 33 ohm resistor on it and soldered the other end of the resistor to pin 64 of the MMU chip, This STFM has now 4 mb of RAM 
. I also soldered a Blitter on this board. And, also has the PAK68/2 on it.
As your board is through hole, you could connect the A9 line on the underside of the board.
. I also soldered a Blitter on this board. And, also has the PAK68/2 on it.As your board is through hole, you could connect the A9 line on the underside of the board.
Re: C103175 REV 1 (520 STFM)
Posted: Sat Apr 07, 2018 9:02 am
I have some 256x4 SOJ chips laying around that I had planned on stretching to fit DIP20 sockets - but your post got me thinking maybe I should dig up some 1Mx4 instead, thanks.redhawk668 wrote: ↑Fri Apr 06, 2018 9:42 pm This looks a lot like my C103414-001 board. It has the same IMP chipset, layout is similar only on your board the memory is through hole. On my board, the memory is also SMT. The pinout of those DRAM’s should be the same as on mine, only the package is different. On my board, we’ve removed the 256kx4 DRAM’s and replaced them with 1Mx4 DRAM’s, we also filled the memory bank next to it with 1Mx4 DRAM’s, so in total 8 DRAM’s on the board. Pin 5 on the DRAM chips is A9, connected them together, joint the two wires, soldered a 33 ohm resistor on it and soldered the other end of the resistor to pin 64 of the MMU chip, This STFM has now 4 mb of RAM
As your board is through hole, you could connect the A9 line on the underside of the board.
Re: C103175 REV 1 (520 STFM)
Posted: Sat Apr 07, 2018 6:25 pm
You’re welcome
Re: C103175 REV 1 (520 STFM)
Posted: Sun Apr 15, 2018 2:08 pm
... and, done: https://www.exxosforum.co.uk/forum/viewt ... f=15&t=769
Re: C103175 REV 1 (520 STFM)
Posted: Fri Nov 08, 2019 3:28 pm
One of mine.. Looks like someone's tried to upgrade to 1MB at some point.
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