Thanks for the memory

When Hyperion Entertainment announced in a 2014 blog article that AmigaOS4 was going to get support for accessing memory beyond the 2 GB limit, the reactions were mixed. Predictably, the most abrasive comments came from people who had never owned an OS4 system; but the camp of supporters didn’t seem over the moon, either.

September 18, 2022 - Amiwest 2022 September Update 2

  • By: AmiWest
  • Posted on: 19 September 2022

One month till the show! Posted a big update on our news/blog page. We did an interview with , we have a new exhibitor, hotel pricing ends September 19th, and the banquet menu and ticket details are posted. Check out all the updates by clicking read more below.

September 2, 2022 - Amiwest 2022 September Update 1

  • By: AmiWest
  • Posted on: 3 September 2022

The show is 50 days out. Lots of great things happening. We are excited to announce that RJ Mical will be attending Amiwet in 2022. The schedule page has been updated with RJ and all our great presentors so far. In addition to the speakers we also have a new exhibitor showing several ReAmiga boards and his own C64 work. Check out all the updates by clickinh read more below.

Identify PAL inputs and outputs

In order to properly reverse engineer a PAL, you need to correctly identify which pins are inputs, and which pins are outputs. This in some cases is trivial because some of the PAL’s pin functions are fixed. Let’s look at the example of a PAL16L8.

Understand the system

Of all of the different techniques this one may be the simplest but also the most important.

When you’re trying to reverse engineer something, understanding the system is key to unraveling the black box which is the PAL. You need to understand what connects to the PAL on the inputs, what it connects to on the output side. Usually going one level back isn’t enough. Why? Because maybe the PAL connects to an OR gate, that then takes a couple other connections. So what you need to do is follow from the primary driver to the consumer of that signal.

Why simply “dumping” a PAL isn’t always possible?

Rom Dumping

Dumping ROMs is a pretty common practice in the space of reverse engineering, and many eeprom readers are cheap, easily available, and there’s really not much to them. Plunk your ROM chip in the reader, press, go, and you have a binary file with the contents. Provided that your reader supports the ROM chip, or you need an adapter like I built in this post to read Commodore Amiga ROMs in a TL866A:

New Reverse Engineering PALs page

I’ve recently put a new page online on the site. It hosts a basic outline on different techniques to enable one to reverse engineering a PAL, and produce a modern equivalent.

Right now, there are about a dozen topics/techniques, with no content beyond basic background information.

As time goes on, I’m going to add more and more posts, with the page serving as the outline, index, with centralized links.

My PAL stimulator

If you’ve been following my blog, you’ll see that I’ve been reversing a Commodore Amiga SCSI HDD Expansion card called the Dataflyer. On that Dataflyer, there’s a PAL that handles address configuration (the latch), chip selects, and converting the 68000 signals to those the peripherals understand.

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