ZX Spectrum – Interesting Features and Details

The Spectrum utilizes a Zilog Z80 A CPU running at 3.5MHz (or NEC D780C 1 clone).  The Spectrums original model featured 16KB (16×1025 bytes) of ROM plus 16 KB or 48 KB of RAM.  Richard Altwasser of Sinclair Research was the hardware designer, while Rick Dickinson, Sinclair’s industrial designer, designed the external appearance.

The video output uses a RF modulator with the purpose of using it with contemporary portable television sets for a simple color graphic display.  The user has different options on how they want their text to be displayed.  They can choose ZX Spectrum’s character set, where there are 32 columns x 24 rows, or they can choose from a 15-shade palette, which includes seven colors with each having 2 levels each, plus black.  The Spectrum also has an image resolution of 256×192 with the same color limitations.  Correspond to the character cells, color has separate storage from the pixel bitmap in a low resolution (32×24 grid overlay) to preserve memory.  In other words, one foreground color and one background color is shared by all pixels of an 8×8 character block.  A patent was received by Altwasser for this design.

zx128_interfacesThe machine’s Sinclair BASIC interpreter was written by Steven Vickers who was on contract from Nine tiles Ltd.  The interpreter along with the fundamental system – routines is stored in the ROM.  BASIC keywords marks the Spectrum’s chiclet keyboard. In simpler terms when you press “G” during programming mode, the keyboard is also inserting the BASIC command GOTO. 

One thing that separatesthe Spectrum BASIC from the ZX81 is that it features lower-case letters. Extra keywords for advanced display and sound, and supported multi-statement lines. It has a cassette interface that can save and load five times faster than the ZX81 (1500 bits per second compared to 307), and it can maintain the TV display during tape storage and retrieval operations.  Also, it can save the contents of the arrays, of the screen memory, and of any defined range of memory addresses.

One of the ZX Spectrum’s most distinct features were its rubber keyboard, minuscule size, and its distinctive rainbow motif.  If one owned the 16 KB model, they could purchase an internal 32 KB RAM upgrade, which consisted of a daughterboard for early “Issue 1” machines.  A fitting of an 8 dynamic Ram chips and a few TTL Chips were required for later issue machine. To be upgraded to 48 KB versions, it was required for the 16K Spectrums to be mailed to Sinclair.  Later models had 64 KB RAM packs, but due to configuration, only the 48 KB were usable.  Soon, external 32 KB RAM, which featured a mountable rear expansion slot, were available via third parties.  Sixteen kilobyte of onboard ROM was available for both machines.

Over 24,000 titles had been released for the Spectrum family by July 2012.  The library included games, databases, word processors, programming language implementations, drawing and painting tools, spreadsheets, and even 3D-modeling and archaeology software and other types.   

bluetooth_zx_spectrum_iphone_iplayer1Despite some limitations, the early Spectrum model earned some success as a game platform. These models lacked many features, such as built-in joystick ports, color support optimized for text display, and primitive sound generation.  Needless to say, video game designers needed much creativity to overcome the platform’s limitations. 

Spectrum included a simulation program called Evolution, also known as Foxes and Rabbits.  Its name derives from the nature of the games.  The population of foxes would decline due to the population of rabbits being too small to provide sufficient food.  When the foxes became too few, the population of rabbits will increase, and then the cycle would keep going.  The player would nominate a number of rabbits and foxes to start and would then watch the population graph rise and fall.  The simulation could be paused at any time and be saved to an audio cassette by pressing the ‘Record’ button on the connected remote tape recorder. When ready to return, the player could start at the saving point.

The 90th issue of GameMaster, a British gaming magazine, stated that the top ten games released were

  1. Head Over Heels
  2. Jet Set Willy
  3. Skool Daze
  4. Renegade
  5. R-Type
  6. Knight Lore
  7. Dizzy
  8. The Hobbit
  9. Way of the Exploding Fist
  10. Match Day 2

Leave a Reply

Your email address will not be published. Required fields are marked *