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How to install a Model III hi-res board in a Model 4 - video

TRS-Ian

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Sep 10, 2011
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Melbourne, Australia
Hi, I had the board left over from a damaged Model III so decided to install it in a Model 4.

Used the instructions from Ira's web site. Works great!


Discuss.

Ian.
 

TRS-Ian

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Only found one app which doesn't work so far, Dog Catcher.

Fractals, Spirograph and Surface plot all work. I'll be writing an article about this in TRS8Bit upcoming issue and maybe a list of software and where to download it from in a subsequent issue.

Ian.
 

gonk23

Experienced Member
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Jun 15, 2013
Messages
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Location
Melbourne, Australia
Only found one app which doesn't work so far, Dog Catcher.

Judging by your next video, it looks like you got it to work.

I'll be writing an article about this in TRS8Bit upcoming issue and maybe a list of software and where to download it from in a subsequent issue.

An article on Model III/4 hires software would be great!

I assume that technical bulletin from Ira's site (http://www.trs-80.com/wordpress/zaps-patches-pokes-tips/hardware/#m3graphics) was mainly used by RS technicians to get an already installed Model III hires board working again after installing the Model III to 4 upgrade kit.
 

TRS-Ian

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Sep 10, 2011
Messages
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Yep, have been testing everything I can find hi-res, and it all works. Dog Catcher just needed me to recall how to load it...

I wouldn't mind if people were able to email me if they have hi-res TRS-80 software in particular xT.CAD

I'm thinking of putting together FreHD images with hi-res software collection so as people locate and install hi-res board on their machines they have a ready supply of software for them.

Cheers,

Ian.
 

jltursan

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Sep 24, 2010
Messages
761
Location
Madrid, Spain
I must say that right now, I'm DoE (death of envy) :D

I'm looking for a M4 Hires card and figured out that MIII cards doesn't work, it's great to know that I was wrong. Never noticed there was an article about the conversion in Ira's site :oops:
 

gonk23

Experienced Member
Joined
Jun 15, 2013
Messages
196
Location
Melbourne, Australia
The mod to the M3 hires card effectively excludes the 8Ch-8Fh ports. Normally the M3 hires card lazy address decodes so that the CRTC registers (ports 88h and 89h) are quad addressed (mirrored) in the 88h-8Fh range. This isn't a problem with the M3 because it doesn't use ports 8Ah-8Fh for anything.

However the M4 tech ref manual lists ports 8Ch-8Fh as "Graphics Sel. 2", and these are sometimes called the "undocumented" M4 hires ports (actually documented on p189 of https://archive.org/details/TRS80Model4PServiceManual and summarised at http://www.tim-mann.org/trs80/ports.doc.txt). So if M4 software tried to use these ports with an unmodified M3 hires card, then potentially the CRTC registers would be sent rubbish data causing all kinds of problems. The mod to the M3 hires card prevents this from happening.

I'm not really sure what the mod to the M4 mainboard is doing, however it's effectively stopping the DOT* signal (which appears to be a sync signal) from being used. The relevant part (U22 pin 12) is shown in the schematic on p35 of the M4 tech ref manual (26-2110). As a hunch perhaps it's disabling the sync from the M4 mainboard because presumably the M3 hires card has its own sync? Maybe someone who knows more about video electronics can explain.
 
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TRS-Ian

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Sep 10, 2011
Messages
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Location
Melbourne, Australia
Found a problem, most of the hi-res software comes from Micro-labs Inc. They have their own operating system, Rapidos, which is incompatible with LS-DOS/LDOS..

Can anyone point me in the direction of where to locate information on ways to convert Micro-Labs titles to LS-DOS, or just the titles themselves?

Cheers,

Ian.
 
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