5MHz Upgrade hacks

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Can we speed up the Model T? Apparently!

I have been investigating various ways to make the Model T run … faster.

Currently I have fixed 5hMz upgrade solutions for

  M100 running NSC800 CPU

I am currently working on a software switched solution where you can change between stock clock and turbo modes using a simple OUT command in BASIC.

As I test and more-or-less land on a reasonable upgrade process, I will post instruction files here If you have any questions, please get in touch with me at Twospruces at --the google mail service.

What are the tradeoffs?

When installed, your laptop will be running at 2x clock speed. However, the system clock remains unchanged.

  1.  Processor, memory, LCD, I/O. BCR are all running at 5MHz
  2.  The serial port, modem and printer ports are unchanged
  3.  Cassette port will not work correctly.  It will be 2x faster. (makes the case for a switchable solution).

What about compatibility with REX#/REXCPM?

REX# and REXCPM from November 2021 are built and tested compatible with 5MHz. In fact my test station runs at 5MHz. If you have an earlier REX#/REXCPM, contact me to discuss what to do.

What do you need?

  Some hardware skills - soldering, PCB modification etc.
  a clock divider circuit board
  a small number of parts (depending on the solution)
  a 9.803 HC49 crystal


Take a look at the instruction files below. Please don't try this if you are not confident of success! I welcome feedback and comments. Especially if you find errors or improvements.

Fixed 5 MHz upgrade for T102 (note - must add part numbers and a link to the Oshpark PCB) : T102 5MHz mod V1 Nov 2021.pdf

coming soon - M100 fixed upgrade, software switchable solutions