Sega Master System

The Sega Master System had better graphics and sound than the NES. It didn’t matter. Nintendo’s two-year head start, exclusive licensing deals, and Mario’s appeal proved insurmountable in North America and Japan. In Europe and Brazil, the story was different—the Master System thrived where Nintendo stumbled.

Fast facts

Manufacturer: Sega.
Released: October 1985 (Japan), 1986 (US), 1987 (Europe).
CPU: Zilog Z80 at 3.58 MHz.
Graphics: a TMS9918a with a new mode bolted on — see below.
Resolution: 256×192 pixels.
Colours: two 16-colour palettes, one for background and one for sprites, drawn from 64 — two bits each of red, green and blue.
Sound: Texas Instruments SN76489 (3 tone + 1 noise).
Sprites: 64 sprites, 8 per scanline.

The video chip is an MSX chip with a fifth mode

The Master System’s VDP is not a new design. It is the TMS9918a — the chip in the MSX, the SG-1000 and the SC-3000 — with one mode added:

For the Master System, this chip was extended by adding mode 4; it was again modified for the Game Gear VDP and was the basis for the Mega Drive VDP.

That is a single video lineage running from a 1979 Texas Instruments part through the MSX, the SG-1000, the Master System and the Game Gear, and arriving at the Mega Drive. Sega did not replace the chip for a generation and a half; it extended it.

Modes 0 to 3 are the original TMS9918a modes and remain present — “seen in SG-1000 and SC-3000 software” — so a Master System is still, underneath, a machine that can display an SG-1000 screen. Mode 4 is switched on by “setting bit 2 of VDP Register 0”, and it is what almost every Master System and Game Gear game uses.

What mode 4 adds:


Resolution	256×192; later VDP revisions added 256×224 and 256×240
Tilemap	32×28 characters of 8×8 pixels
Colour	16-colour tiles from two redefinable palettes
Sprites	64, each 15 colours plus transparency, 8×8 — maximum 8 per line
Scrolling	per-pixel, X per line and Y per frame, with scroll lock
Also	line interrupts, left column masking

The eight-sprites-per-line limit is the one that shows. It is the same constraint the NES has, and it is why Master System games flicker in crowded moments despite the machine’s larger sprite budget.

One detail carries a warning: the taller 224 and 240-line modes “do not work properly on Mega Drives” — a compatibility seam inside Sega’s own lineage, since a Mega Drive plays Master System cartridges through the same VDP ancestry.

Sixty-four colours, six bits

The palette format is unusually plain. Each colour is one byte, “two bits each for red, green and blue … packed in the form %00BBGGRR” — six significant bits, so 64 possible colours, of which 32 are loaded at a time as two 16-colour palettes, one for backgrounds and one for sprites.

Six bits also means the brightest white is simply all of them set: “for the SMS, setting all six colour bits makes white.”

Four bytes that are both RAM and hardware

The memory map holds a piece of economy worth seeing. The cartridge occupies $0000-$bfff through three mapper slots, system RAM sits at $c000-$dfff and is mirrored at $e000-$ffff — and the mapper’s control registers live at the very top of that mirror:

Address
`$fffc`	cartridge RAM mapper control
`$fffd`	mapper slot 0 control
`$fffe`	mapper slot 1 control
`$ffff`	mapper slot 2 control

Because those addresses are also RAM, writing to them does two things at once:

Where control registers overlap with mirrored RAM, values written will affect the device and also be written to RAM. Reads simply return the value stored in RAM.

So a program can read back which bank is paged in — not by asking the mapper, which cannot be read, but by reading the RAM the write also landed in. It is free bookkeeping, and it means the last four bytes of the address space can never be used for anything else.

The first kilobyte is likewise spoken for: $0000-$03ff is “ROM (unpaged)”, outside the mapper entirely, because that is where the Z80’s restart and interrupt vectors live. Bank switching cannot be allowed to move them.

And four addresses at $fff8-$fffb are 3D glasses control — hardware support for the SegaScope shutter glasses, sitting in the memory map beside the mapper.

Technical superiority

The Master System outspecced the NES:

More colours: 64-colour palette versus 54.
Higher resolution: Cleaner display.
Better sprites: Larger, more colourful.
FM sound: Optional expansion (built into Japanese Mark III).

Side-by-side, Master System games often looked better.

Nintendo’s fortress

Technical advantages couldn’t overcome:

Exclusivity deals: Third parties locked to Nintendo.
First-mover advantage: NES established before SMS arrived.
Software library: More games, more recognisable franchises.
Retail relationships: Nintendo controlled shelf space.

Regional variations

Success varied dramatically by market:

Japan: Distant second to Famicom.
North America: Failed against NES dominance.
Europe: Strong performer, especially in UK.
Brazil: Market leader, supported until 1990s.
Australia: Competitive presence.

Why Europe was different

The Master System succeeded where NES had weaknesses:

Timing: Similar launch windows.
Distribution: Sega’s European partners were aggressive.
Price: Competitive positioning.
Computer market: Home computers delayed console adoption.

Sega’s own software

Without third parties, Sega developed internally:

Alex Kidd: Attempted mascot, moderate success.
Phantasy Star: RPG showcase.
Wonder Boy: Platform series.
Shinobi: Ninja action.

Quality varied, but highlights showed the hardware’s potential.

The Master System II

Redesigned for budget market (1990):

Smaller, sleeker design.
Built-in Alex Kidd in Miracle World.
Continued European sales into mid-1990s.
Brazil model produced until 2000s.

Legacy

The Master System taught Sega lessons applied to the Mega Drive: technical superiority alone doesn’t win. You need games, marketing, and timing. In markets where they got those right—Europe, Brazil—the Master System succeeded. Where they didn’t, it foundered despite better hardware.

The NES challenger