---
title: "Hardware Project: Simple 4K-8K ROM Switch"
type: "article"
slug: "hardware-project-simple-4k-8k-rom-switch"
url: "http://localhost/article/hardware-project-simple-4k-8k-rom-switch/"
markdown_url: "http://localhost/article/hardware-project-simple-4k-8k-rom-switch.md"
published_at: "2026-03-13T00:25:03+00:00"
modified_at: "2026-03-13T00:25:04+00:00"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "Step-by-step guide for building a piggyback ROM switch to run both 4K integer BASIC and 8K ROMs in the ZX80 without swapping chips. Uses a single-pole switch mounted inside the ZX80 case, with both ROMs soldered together except at pin 24 (Vcc), which is switched to activate one ROM at a time."
category:
  - name: "Syntax"
    slug: "syntax"
    taxonomy: "category"
    url: "http://localhost/category/periodicals/syntax/"
post_tag:
  - name: "Hardware project"
    slug: "hardware-project"
    taxonomy: "post_tag"
    url: "http://localhost/tag/hardware-project/"
  - name: "ZX80"
    slug: "zx80"
    taxonomy: "post_tag"
    url: "http://localhost/tag/zx80/"
model:
  - name: "Sinclair ZX80"
    slug: "zx80"
    taxonomy: "model"
    url: "http://localhost/model/zx80/"
indiv:
  - name: "Martin Oakes"
    slug: "martin-oakes"
    taxonomy: "indiv"
    url: "http://localhost/indiv/martin-oakes/"
publication_r:
  id: 10246
  title: "Syntax"
  type: "periodical"
  url: "http://localhost/periodical/syntax/"
authors_r:
  - name: "Martin Oakes"
    slug: "martin-oakes"
    taxonomy: "indiv"
    url: "http://localhost/indiv/martin-oakes/"
volume: "3"
issue: "7"
issues_articles:
  - id: 52481
    title: "Syntax/Syntax ZX80 v3 n7"
    type: "issue"
    url: "http://localhost/issue/syntax-syntax-zx80-v3-n7/"
pages: "8"
pubdate: "July 1982"
archive_link: false
---

# Hardware Project: Simple 4K-8K ROM Switch

Step-by-step guide for building a piggyback ROM switch to run both 4K integer BASIC and 8K ROMs in the ZX80 without swapping chips. Uses a single-pole switch mounted inside the ZX80 case, with both ROMs soldered together except at pin 24 (Vcc), which is switched to activate one ROM at a time.