The Rainbow Plus Spectrum Interface
Damco Enterprises
67 Bradley Ct.
Fall River, MA 02720
T/S 2068; $49.95
You can count the numer of ways to run Spectrum software on one hand. If you don’t want to to to the expense of purchasing a Spectrum Computer, then there are only four:
1. Replace your T/S 2068 ROM with a Spectrum ROM.
2. Use both ROMs, selecting between with a switch.
3. Use an “emulator” that plugs into the cartridge port.
4. Use an “emulator” that plugs into the expansion port.
The first two choices require opening the computer, voiding its (ha!) warranty. Many of us just won’t chance messing up our computer through accident or ineptitud. But we’re not averse to plugging in something. We’ve had experience with that technique.
The last two choices involve tying up either the cartridge port or the expansion port. This prevents its use by other peripherals. The choice of which port to use for Spectrum emulation is a matter of what else you want to accomplish.
The Rainbow Plus Interface is a small black box which plugs into the 2068 expansion port. A switch on the left rear changes its operating mode from T/S 2068 to Spectrum. Instructions advise powering off the computer before installing the interface.
The Rainbow Plus Interface allows the access to the whole line of Spectrum software, but that’s not all it does. Its operating system is on an eprom. This makes possible the correction of some flaws in the Spectrum ROM. The Rainbow Plus also has a Spectrum compatible edge connector. This renders the entire line of Spectrum hardware peripherals available as well.
When you turn on the computer with the interface in Spectrum mode, your computer first initializes in T/S 2068 mode. Then it re-initializes in Spectrum mode. Instead of the normal copyright notice, you see “Sinclair Spectrum Mod. B.”
This modification refers to the fact that several known bugs in the Spectrum ROM have been fixed. One unexpected feature is the inclusion of 21 user-defined graphics symbols. They include the superscripts 0-9, six letters from the Greek alphabet, and five other symbols of marginal utility.
In this mode you can load Spectrum software. All 24 of the programs I tried, loaded with no difficulty. I had a nice suprise with the PAINTBOX graphics utility and drawing program. Paintbox has 84 udg’s that are available. Along with the 21 already contained in the Rainbow Plus eprom, my version of Paintbox now has 105 udg’s that can be edited, used, and saved to tape.
I also had the opportunity of testing a couple of Spectrum peripherals with the interface. The DK’Tronics Light Pen and the DK’Tronics Sound Synthesizer worked equally well. I will report in detail on these peripherals in subsequent reviews.
While the Spectrum compatible hardware works fine, it should be noted that T/S 2068 hardware does NOT work when attached to the rear of the Rainbow Plus. A TS 2068 printer interface, for example, must be attached first to the computer. Then the Rainbow Plus can be piggy-backed onto the TS 2068 hardware.
Two exceptions to 2068 hardware incompatability with the Rainbow Plus interface should be noted. The 2040 thermal printer and the 2050 modem CAN be used behind the Rainbow Plus.
I find the Rainbow Plus Interface, extraordinarily easy to use. Installation on the expansion port is easier than opening up the computer. In operation it’s more reliable than some other devices. By this I mean that the Spectrum mode initializes 100% of the time. This is not so with the ROM switching technique.
The use of the expansion port is a problem for me. My parallel printer interface doesn’t have a rear edge connector of its own. I can’t plug it in first and then attach the Rainbow Plus. But that’s a problem with my printer interface, not with the Rainbow Plus.
The eprom operating system with the corrected bugs and stored udg’s is superior to other devices which employ a standard Spectrum ROM. Its software compatibility and firmware features, coupled with support of Spectrum hardwar devices, make the Rainbow Plus Spectrum Interface the optimum choice among several possibilities for Spectrum emulation.