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<p>You know, I have been racking my brains from time to time and I
can't remember a thing about the ADP modifications to the 2020.</p>
<p>So, the 2020 came with a maximum of 512K words, 2**9. An
addition bit would have brought it up to a full megaword, 2**10,
which is quite reasonable for the target audience (some kind of
installation that didn't hold stock in the local power utility).<br>
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<p>I guess there may have been modifications to the 2020 build of
the monitor to allow for the extra bit. I don't know if the
Unibus devices could do DMA into the full address space.</p>
<p>Did you pick up any software with these little jewels? The
monitor changes might be interesting.<br>
</p>
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<pre class="moz-quote-pre" wrap="">On 4/24/20 12:12 AM, Dave McGuire wrote:
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<pre class="moz-quote-pre" wrap=""> Nice!
One of our 2020s is in the brown color scheme. You know what that
means: ADP, and one more address bit.
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<pre class="moz-quote-pre" wrap="">On 4/23/20 6:15 PM, Thomas DeBellis wrote:
The solution for 4.1 was one of the finest hacks I have ever heard of;
while the 2020 doesn't support extended addressing, it does support
multiple address spaces, so what they did was move all the symbols into
a separate address space. This was called 'hiding' symbols and I
thought it was great because it made them harder to smash. However, all
of that went out the window with 5.0, which fully supported extended
addressing.
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