5-24-25 progress

Author: thecodingchicken

_posts/2025-05-24-progress.md

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+## MAR Progress
+
+Starting tonight by wiring up the MAR, I'm going with two [74hc377's](https://www.jameco.com/Jameco/Products/ProdDS/45858.pdf).  Why?  Because that's what I'm using.  I had some reason, it's either on a previous day or what someone else used.  
+Either way, time to hook them up.  I had started with the MAR on top of the rom&ram, but I decided to swap that around to hopefully help a bit with the wiring, so I don't have _as many_ wires crossing over chips.  That'll help with neatness as well.  Heh, I need that.   
+
+
+---
+<figure>
+  <div>
+  <img src="{{site.url}}/assets/img/20250524_222318.jpeg" alt="current progress"/>
+  </div>
+  <figcaption>{{"current progress"| markdownify}}</figcaption>
+</figure>
+
+End of day update.  It's late, I need some sleep, etc
+I hooked up the MAR's 377 outputs to the ram chip, as well as running the common io lines of the ram chip to the right side of that breadboard.  I changed my mind a couple times while doing this, the fact that the ram&rom chips are both 3-state certainly helps, so they're each like buffers.  
+I don't have the rom chip yet, it's supposed to arrive sometime this next week(the 27th), but I'm going to pre-wire it up.  I've decided to go with 4k rom/28k ram.  That technically leaves 32k of space on the table, but I think this is good enough for now.  I can always find space somewhere nearby(perhaps on that spare clock board) if I want to add another 32k, but I don't think I will.  32KB of ram is plenty, especially for a 8/16 bit computer.  I think I'll get rid of the memory LEDs on that breadboard, since that's now 3-state and not active all the time.  
+
+Gn