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ZX Spectrum Hardware Do it yourself

In early 80-es Sinclair launched for that time very cheap microcomputers. It was result of simple construction and usage of custom (ULA) chips. Most success he gained with model Spectrum. There is still lot of them worldaround, many in good condition.
Due to simple and opened architecture it's very applicable for experimenting with diverse upgrades.
I think that even today it may be interesting, especially for beginners and people who had earlier got Spectrums.

Following projects are all realized, and work reliable for less-more long time. Most of them is made (and tested) on 48K model, but they should also work on 128K models.


IDE hard disk interface

Scheme - note: here is Spectrum Edge connector layout. ... Zxide.jed

Download ROM example (14KB)

Programming reference

Simpler interface

Spectrum 128K compability

IDE reference

Pic. of interface

Pic. of Speccy with drive

Smart Media card interface

Scheme & introduction

Pic. of prototype

UVY-RGB converter for 48K models


ROM switch

Description & scheme

Flash EPROM instead ROM

Scheme & description

Floppy interface

Scheme Note: Modified on 26. May '98 for compatibility with Spectrum 128.

ROM image with brief instructions & format program

How to use ROM

File format structure

External ROM modul


EPROM programmer

This is not for Spectrum - it's for PC (or other computer) with standard bi-directional parallel port.

EPROM programmer


NMI button

Technical info about Spectrum

Port addresses for interfaces and peripherals. Waste of bits. This is not list of port addresses by popular peripherals/interfaces. I try giving here some explanations of used systems, and how designing address decoders and using which addresses.

CCT diagram of Spectrum 128

Following section is intended for authors of Spectrum emulators. I included here only results of my research:
Cassette/EAR/MIC port. Issue 2 and 3.

Useful links

Spectrum emulators for PC site - tests of various Spectrum emulators -NEW!

The World of ZX-Spectrum - most complete and best-maintained Spectrum related site on WEB.

Z80 CPU Official Support Page - many data about Z80. - IDE hardware reference. IDE hard disk commands. - 48K scheme etc.

The ZX Spectrum Technical Information Repository - site with circuit diagrams of Spectrums. - here is free PCB design program for PC.

GAL related links:   File GAL-ALGS.PGM contains very simple programmer project, and infos about diverse GALs.  .  - RGBPLD21.ZIP , plus other digital electronic projects.

Send me mail with questions, suggestions and comments about this site.

Sir Clive & T.Rex

Issue4.jpg - 48K board in resolution of 1588x2549. File length is 800KB.

Copyright: Pera Putnik.
Last revised: 28 May. 2005.

Spectrum Webring site by Pera Putnik
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