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How to...
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Written by Martin Gierich
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Monday, 15 December 2008 13:48 |
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The virtual Plus 4
How many times have you heard from PLUS/4 fans, "Your C16 is only good as a PLUS / 4 parts depot"? How many times have you been offerred money for your C 16 by these same TED-chip-seeking adepts? Disregard temptation because now your C16 can be turned into the pseudo-equivalent of a PLUS/4 with the ability to run a great deal ofPLUS/4 software, You see, the C16 and PLUS /4 belong to the "264" series of Commodore machines. The C16 is actually a PLUS /4 with a few chips missing, notably the 6551 UART (and userport) and a full 64 KB of memory. In this article, we will be upgrading a C16 to a full 64 KB, allowing us to run many PLUS/4 or "generic 264" software (minus userport-terminal programs and some assorted misc. software).
Important!
Before starting read this carefully and check out the schematlcs in your CI6 manual. You should be familiar with soldering. I have reconstructed this, it is about 10 years since I have done this. I can give you no warranty, do it on your own risk! Neither myself nor the staff of the dlsC=overy journal is responsible for any use or misuse of informatlon presented in this article.
- Buy two 64x4 bit dynamic RAM chips llke "TMS 4464" or "41464". They should cost less than US$10 together.
- Remove your two old ''TMS 4416" RAM chips from your C16. They are labelled U5 and U6. You might destroy them, but be careful to not destroy something else! I have used scissors to cut the pins and then I have desoldered the pins.
- Now solder two 18 pin sockets in where the old RAM chips have been. Again do it carefully to avoid destruction! Check out where pin 1 is. Then plug In the new RAM chips.
- Check everything again, then switch on your C16. It should still show "12KB free".
- Adress lines A0 to A13 are connected to the multiplexers U7 and U8. You need to connect A14 and A 15 to them instead of +5V at U7 pin 2 and U8 pin 14 (but the +5V connections at pin 16 must be left). For example get them from the CPU (U2) pin 21 and 22. First scratch the +5V connections, U8 pin 14 is connceted on the lower side only and should be easy to disconnect. U7 pin 2 is more tricky. Disconnect the line between pin 2 and pin 16 at pin 16 on the upper side (U7). Pin 16 still gets +5V from the lower side.
- Now you have two choices:
- To always have 64KB:
Connect U7 pin 2 with U2 pin 21 (A14).
Connect U8 pin 14 with U2 pin 22 (A15).
- To choose between 16KB and 64KB:
You need a double switch (or whatever this is called. it has 6 pins). Connect U7 pin 2 and U8 pin 14 to the two middle pins of the switch. Connect U2 pin 21 and 22 to the two upper pins of the switch. Connect +5V or Ground to the two lower pins of the switch. With that you can chosse where your 16KB area is located in your 64KB area. I have used FB 13 to get Ground and FB 14 to get +5V.
- Check everything again carefully. Then switch on your C16. It should show "60KB free" if the switch is in right position.
- It is a good idea to replace the 7805 (labelled VR1) with a 78S05. because the 7SS05 switches itself off. if it gets too hot.
Remember to keep the connections short.
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Last Updated on Tuesday, 16 December 2008 14:27 |
I would like to know where can i buy 64K Video Ram chip Adapter board for flat C128?
Because in EBay they don't carry them anymore or sale them any longer. I live in NY city area and I would like to have that board chip.
I also have two 1571 disk drives and some time the disk drive won't load some of the new software program, it just froze there nothing going on so i have to reset the flat C128 every time. :(
Please tell me soon.
Thank You!
go to http://www.commodore128.org and read the forums. You'll find all the info you need.