---
title: "PC8300 Timex ROM"
id: 25070
type: "product"
slug: "pc8300-timex-rom"
url: "http://localhost/product/pc8300-timex-rom/"
markdown_url: "http://localhost/product/pc8300-timex-rom.md"
published_at: "2020-03-27T14:07:43+00:00"
modified_at: "2026-03-22T13:13:15+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "Custom adaptation of the Timex/Sinclair 1000 ROM for the Lambda 8300 computer. Adapted by Fred Nachbaur, the replacement EPROM came in a 2764, a 28-pin device (several additional pins were necessary for programming EPROMs). The PC8300 ROM was a 24-pin 8K ROM. In order to fit the replacement EPROM to the PC8300, several pins were…"
category:
  - name: "ROM"
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    taxonomy: "category"
    url: "http://localhost/category/hardware/rom/"
post_tag:
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - name: "Lambda 8300"
    slug: "pc8300"
    taxonomy: "post_tag"
    url: "http://localhost/tag/pc8300/"
  - name: "Silicon Mountain Computers"
    slug: "silicon-mountain-computers"
    taxonomy: "post_tag"
    url: "http://localhost/tag/silicon-mountain-computers/"
model:
  - name: "Lambda 8300"
    slug: "lambda-8300"
    taxonomy: "model"
    url: "http://localhost/model/lambda-8300/"
indiv:
  - name: "Fred Nachbaur"
    slug: "fred-nachbaur"
    taxonomy: "indiv"
    url: "http://localhost/indiv/fred-nachbaur/"
genre:
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  - name: "ROM"
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    taxonomy: "genre"
    url: "http://localhost/type/rom/"
creator_indiv:
  - name: "Fred Nachbaur"
    slug: "fred-nachbaur"
    taxonomy: "indiv"
    url: "http://localhost/indiv/fred-nachbaur/"
company:
  id: 20332
  title: "Silicon Mountain Computers"
  type: "company"
  url: "http://localhost/company/silicon-mountain-computers/"
price: 14.95
date: 1987
rarity: "Uncommon"
related_content:
  - id: 35527
    title: "PC8300 “Timex” ROM Documentation"
    type: "document"
    url: "http://localhost/document/pc8300-timex-rom-documentation/"
  - id: 35528
    title: "Silicon Mountain Computers catalog"
    type: "document"
    url: "http://localhost/document/silicon-mountain-computers-catalog/"
  - id: 15423
    title: "A Letter From Fred Nachbaur (concerning the PC8300 “Timex Clone”)"
    type: "article"
    url: "http://localhost/article/a-letter-from-fred-nachbaur-concerning-the-pc8300-timex-clone/"
  - id: 42643
    title: "Incredible Add-On Device Turns TS1000, ZX81 and PC8300 Into Versatile and User Friendly Computers"
    type: "article"
    url: "http://localhost/article/incredible-add-on-device-turns-ts1000-zx81-and-pc8300-into-versatile-and-user-friendly-computers/"
  - id: 15388
    title: "Inside the PC 8300"
    type: "article"
    url: "http://localhost/article/inside-the-pc-8300/"
  - id: 44947
    title: "More on the PC8300"
    type: "article"
    url: "http://localhost/article/more-on-the-pc8300/"
  - id: 22817
    title: "The Musical PC8300"
    type: "article"
    url: "http://localhost/article/the-musical-pc8300/"
image_gallery:
  - url: "http://localhost/wp-content/uploads/2020/07/PC-8300-rom-d.jpg"
  - url: "http://localhost/wp-content/uploads/2020/07/PC-8300-rom-c.jpg"
  - url: "http://localhost/wp-content/uploads/2020/07/PC-8300-rom-b.jpg"
  - url: "http://localhost/wp-content/uploads/2020/07/PC-8300-rom-a.jpg"
related_products:
  - id: 51746
    title: "PC-8300 Timex ROM"
    type: "computer_media"
    url: "http://localhost/computer_media/pc-8300-timex-rom/"
companies_products:
  - id: 20332
    title: "Silicon Mountain Computers"
    type: "company"
    url: "http://localhost/company/silicon-mountain-computers/"
---

Custom adaptation of the Timex/Sinclair 1000 ROM for the [Lambda 8300 computer](https://en.wikipedia.org/wiki/Lambda_8300).

Adapted by Fred Nachbaur, the replacement EPROM came in a 2764, a 28-pin device (several additional pins were necessary for programming EPROMs). The PC8300 ROM was a 24-pin 8K ROM. In order to fit the replacement EPROM to the PC8300, several pins were bent up and connected, and the EPROM was placed in a 24-pin socket.

The images below show the PC8300 ROM with and without socket.

### How to make a modern replacement

You’ll need:

- a modern equivalent of the 2764 EPROM, like the [28C64](https://www.digikey.com/product-detail/en/microchip-technology/AT28C64B-15PU/AT28C64B-15PU-ND/1008529)
- a [socket adapter to convert the 28 pin EEPROM to the 24 pin socket](http://www.go4retro.com/products/23xx-adapter/) in the 8300
- EEPROM programmer

Download the binary image (below) and burn it to the 28C64. Configure your adapter and insert in the 8300.