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RAMBO XL-II Clone of RAMBO 256K Memory Upgrade for the 800XL &1200XL
A very basic 256K upgrade for the XL line, originally produced and sold by ICD. Since these became scarce after ICD closed shop and sold their assets to FTE, which also vanished a few years later, it was time to produce a clone. AtariAge member Dropcheck actually rolled her own, and for a short period of time sold it from her Bits of the Past website, but at the time when I needed a couple, they were no longer for sale. So I cloned it myself after backwards engineering ICD's version, which BTW was based on Claus Buchholz's original design.
Although 74HCTxx chips are shown in the board image, 74LSxx chips will work better, as depicted in the schematic and the board's silk screen.
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My ICD RAMBO XL Clone
Dropcheck's version has also been released which is truer to the original ICD version. Whereas I took some liberties in my interpretation consolidating the individual A,B,C,D wire connections into a single 9-pin 0.1" shared header.
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RAMBO XL-II UPGRADE REQUIRES REPLACING 1200XL 64K DRAMS with 256K VERSIONS
Note: a more modern option for the 1200XL can be seen below.
Note: a more modern option for the 1200XL can be seen below.
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1200XL-1mb 1MB Solder-Less Upgrade for the 1200XL
A Plug 'n' Play fully SRAM 1088K upgrade for the 1200XL, which not only expands the system memory to a whopping 1088K, but also kills much of the noise associated with the original DRAM, thus enabling noise-free video output. By piggybacking 4 existing chips on the 1200XL motherboard (MMU, Decoder, CPU, PIA), all the required logic signals are easily acquired. Thus allowing for a completely solder-less memory upgrade, with full reversibility. No modification other than removal of an RF choke used only by the RF sound section is necessary, assuming it can't be bent over to clear the top part of the board. If you have no plans for RF output, simply cut the choke out of circuit. Presently there is no BOM, so reference the schematic for the necessary components, which can be easily gotten from Mouser or Digi-Key (the 0.1uF capacitors have 0.2" lead spacing, and the 3K resistors are standard 1/4 watt rated).
Thanks goes out to Jurgen (AtariAge member tf_hh) for his great design and contribution of the 1MB EMMU jed file that makes this project possible. All IC sockets used for piggybacking (U5, U6, U7, U9 on the 1200XL-1mb PCB) need to be machine pin type, with an extra socket stacked underneath.
After installing this board, all 4 of the original 1200XL chips that were removed need to be transferred to the top side.
There are two jumper blocks present. For most situations the top one should be set to 1MB (left = 1MB / right = 512K), and the bottom one will be shorted for Extended Memory support (open = stock 64K system). If so desired, switches could be installed with outside accessibility to control these selections. As part of this upgrade, there are 12 chips that need to be permanently removed from the 1200XL motherboard.
Refer to the image below to locate the chips that need removal (they are all socketed). The CO60472 delay line is also not needed, but is often soldered in place, so there's no harm leaving it behind. Although it's rare and could be repurposed. NOTE: This Memory Expansion will also work on a Modified 1200XL having a 800XL MMU and OS, as well as a BASIC Rom. !!! IMPORTANT !!! installation of this SRAM board should only be done with the 1200XL motherboard removed from its case and sitting on a solid surface. |
Top View 1200XL-1mb RAM board
Bottom View 1200XL-1MB Board
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Early Prototype shown, although installation is the same for the latest production boards (Click on Image to Enlarge)
