[Coco] Interrupts

[Bill Pierce]

VRN, FTTD, and VI are modules developed by Bruce Isted to emulate the virtual memory drivers used by King's Quest III, Flight Simulator, Lesure Suit Larry and others. The very early games actually used "illegal" drivers that accessed memory and graphics areas directly. I think Bruces plan was to create "legal" drivers that had the same functions. These drivers use CoVDG (formally VDGInt) and use VDG style of graphics access. In VRN there ar supposedly ways to access virtual memory and use memory out of the 64k workspace that is normally accessed. Later, various programmers found other ways to do this without special drivers such as the virtual memory system used in Ultimuse 3 and others. Most of the later programs just used the get/put buffers and hidden hi-res screens as virtual memory storage as these memory blocks are not mapped into the 64k workspace. All that is needed is an 8k block for get/put buffers to accessed.
Not many people embraced Bruces "VRN" system as the get/put buffers were easier to use and were already in the system where as VRN and it's descriptors had to be installed into the bootfile just for this purpose.

I hope I explained it correctly... I'm sure I'll be corrected if not :-)
Bill P

Music from the Tandy/Radio Shack Color Computer 2 & 3
https://sites.google.com/site/dabarnstudio/
Bill Pierce
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-----Original Message-----
From: rcrislip <rcrislip at neo.rr.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Sun, Dec 2, 2012 3:15 pm
Subject: Re: [Coco] Interrupts


<Snip>

<ignorance show on>

What's VRN?

</ingorance show off>

TIA

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