The Seatronics Super Speed-UpTRS‑80 Model 4. It could double the Model 4 speed to 8 MHz, without requiring any performance sapping memory wait states. The Super Speed-Up was sold by Seatronics, a company based in Maastricht, Holland, for $129.00. (A review in 80 Micro identified Sylvester Technologies of Cypress, Texas as the United States distributor, but that appears to have been a mistake.)
Installation of the Seatronics Super Speed-Up was more involved than other Model 4 speed-up boards. The first step of the installation was simple, consisting of removing the Z80 and plugging the Super Speed-Up board in its place. But subsequent steps involved cutting pins, moving wires, straightening a pin, running a wire, and possibly soldering a resistor. David Dalager in Computer News 80 described the installation as “not for the average computer user.”
Once installed, the speed could be set (either through software or hardware) to 2 MHz, 4 MHz, 6 MHz, or 8 MHz.
The 8 MHz speed of the Super Speed-Up made it the fastest of the Model 4 speed-up boards. Most other commercial Model 4 speed-up options topped out at 6 MHz. (The one exception was the H.I. Tech, Inc. XLR8er. The XLR8er replaced the Model 4’s Z80 processor with the more advanced Hitachi HD64180. Even though the HD64180 ran at 6.144 MHz, its more advanced design meant that that speed was considered equivalent to an 8 MHz Z80.)
Seatronics hinted that the Super Speed-Up was capable of even faster speeds, mentioning in one advertisement that it had been tested at 9.25 MHz during development. I know that some people modified their Super Speed-Up boards to work at 12MHz. One person supposedly increased the speed of his to a staggering 16 MHz!
The Super Speed-Up Board was commonly paired with another Seatronics product, the Megabyte Memory Board. The Megabyte Memory Board was a Model 4 memory expansion that was available in 512K and 1 MB sizes.
Seatronics advertised the Super Speed-Up Board through 1986 and 1987, but it was no longer available by 1989.