It is currently Mon Sep 16, 2019 5:02 am

All times are UTC - 7 hours



Forum rules





Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2
Author Message
PostPosted: Mon Jun 18, 2018 4:46 pm 
Offline

Joined: Mon Jul 02, 2012 7:46 am
Posts: 774
I wonder if it might be possible to reduce the wiring by just disconnecting the high address line from the Cx4 and feeding that directly into the ROM chip (so the Cx4 thinks it's always within the 16Mbit memory space and doesn't tri-state the data lines).


Top
 Profile  
 
PostPosted: Tue Jun 19, 2018 8:19 am 
Offline

Joined: Wed Oct 21, 2015 4:26 pm
Posts: 12
Haven't tried that but it did cross my mind. This was the easier theory to test, because of those data line test points. If that works, a 1-rom solution is easy too. If not, easiest way would probably be to design a custom board and transplant a cx4..


Top
 Profile  
 
PostPosted: Sun Sep 08, 2019 7:41 am 
Offline

Joined: Fri Jul 04, 2014 2:34 pm
Posts: 346
Bumping that topic because I'm currently trying to make my own custom board for that hack.

While using 2x27C160 or 2x29F016 is a neat way and was already found working by zzattack I was thinking to only use one 27C322 for example.

Now my plan is:
Cx4 RD0-RD7 goes to 27C322 D0-D15 (using 2x 74HC257 to decode Lo and Hi)
Cx4 RA0 and /ROE are used to decode Lo and Hi via 74HC257.
Cx4 RA1-RA20 goes to 27C322 A0-A19.
27C322 A20 is controlled by the 74HC139 to switch between lower and upper 2MB of the ROM.

That way the Cx4 should always think it's within 16Mbit, right?


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 6 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group