Blogs

 

All members are invited to blog on Applefritter. Weblogs should generally be of a technical nature and should be written in such a way as to still be readable and useful 50 years from now. Please do not embed outside media. Images and videos can be uploaded via the Media Browser. Files should either be attached to the blog post or uploaded to the file libraries.

 

When you post to your blog it will appear on this index and on your personal blog page. Once you've made a few posts, contact me about having a graphic added on the top of this page.


EPROM data rot in my EPROM programmer's EPROM

I recently discovered that some of my custom EPROMS from the 80's and 90's are exhibiting problems due to EPROM bit rot, which falls under the general category of data degredation...or 'data rot'.  Bit rot causes any programmed 0 bits to revert back to 1 bits, their un-programmed state.  The chip isn't actually harmed, it just loses its prorgamming. 

A very effective Applesoft memory test

Here's a simple-but-effective Applesoft program that rigorously tests main memory.

In its first pass, the program uses Applesoft's pseudorandom number generator to fill addresses 4096 through 49151 ($1000 to $BFFF).

In its second pass, it resets the pseudorandom number generator and computes the same sequence again...but this time it compares the values that were previously stored in memory and detects any that don't match.

(2022) - New Project ideas

I'm aiming a little bit lower for my 2022 projects - keyboard interfaces cards for vintage pre-MIDI music systems, the Passport Designs soundchaser and theI have an existing passport interface card - acquired in early 2022 - which I can clone.Still hoping to find a soundchaser card as well. 

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