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PC-8801 mkII SR

From NEC Retro

PC8801mkIISR logo.png
PC8801mkIISR.jpg
PC-8801 mkII SR
Manufacturer: NEC
Release Date RRP Code
PC-8801 mkII SR
JP		 ¥ ?

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The PC-8801 mkII SR (also referred to unofficially as the PC-8801 SR or PC-88SR) is the second revision of the PC-8801 computer by NEC. It was launched at the beginning of 1985.

Hardware

While the PC-8801 mkII was more of a case redesign than a hardware upgrade, the PC-8801 mkII SR offers a number of improvements over the previous two PC-8801 models while maintaining backwards compatibility. The SR introduces new FM sound hardware, two joystick ports and a brand new "V2 mode" for enhanced graphics. These three features combined made the system more suited to video games than its predecessors, and would become the de-facto standard for PC-8801 games in the coming years.

The PC-8801 mkII SR builds on its predecessors, being able to load and run PC-8001 software ("N mode"), original PC-8801 software (N88 "V1-S mode") and a new library of PC-8801 mkII SR software (N88 "V2 mode"). Also added, though not prominently featured on the unit itself, is a "V1-H mode" ("high speed"), identical in capabilities to the standard V1-S mode, but leveraging the new technology to speed up graphics rendering. Like its predecessors, changing modes requires manipulating physical dipswitches on the front of the unit.

The detection of modes needs to be written into software, and as many developers failed to do so, running programs in the wrong mode can lead to undesirable results. Much of N88-BASIC remains the same between the V1 and V2 modes, and so software designed for V1 mode can often run in V2 mode without issue. Compatibility is guaranteed, however, facilitating the need for extra modes; V2 mode can lead to incorrect colours in V1 sofware, and software designed with the precise timing of the stock PC-8801 may not function correctly outside of V1-S mode.

Running software optimised for V2 mode in either of the V1 modes is also sometimes possible, but the success rate is much lower. V2 games often exhibit severe graphical corruption in V1 mode, or will render in monochrome (if the game even boots at all); it is common for games made after 1985 to check which mode was set on startup before running, displaying a "V2 only" message if the mode was required. This could not be applied retroactively to PC-8801 software that pre-dated the mkII SR, meaning the user has to be wary of the current state of the computer before loading a game.

The mkII SR adds a YM2203 chip for FM sound, which became not only a standard for mkII SR games, but newer PC-8801 titles that could tap into the hardware if played on a mkII SR.

Like the mkII, the SR was sold in three configurations; the model 10 (no drives), model 20 (one double-density drive) and model 30 (two double density drives). This machine, and the very similar PC-8801 mkII TR, were the last computers to be produced by NEC that maintained compatibilty for PC-8001; newer revisions would axe this mode to reduce production costs.

Technical specifications

List of games

References



PC-8800 series hardware
PC-8801 (1981) | PC-8801 mkII (1983) | PC-8801 mkII SR (TR | FR | MR | FH | MH | FA | MA | FE | MA2 | FE2 | MC) (1985-1989) | PC-88 VA (VA2 | VA3) (1987-1988)
stuff
haven't worked it all out yet
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