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README: notes about the disk copy overlays

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Joshua Bell 2018-05-07 12:43:24 -07:00
parent 4ffa58fac8
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desktop/README.md
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@ -29,7 +29,7 @@ The file is broken down into multiple segments:
| DeskTop | B$008580 | Aux LC | A$D000-$ECFF | L$1D00 | `desktop_res.s` |
| DeskTop | B$00A280 | Aux LC | A$FB00-$FFFF | L$0500 | `desktop_res.s` |
| DeskTop | B$00A780 | Main | A$4000-$BEFF | L$7F00 | `desktop_main.s` |
| Initializer | B$012680 | Main | A$0800-$0FFF | L$0800 | `desktop_main.s` |
| Initializer | B$012680 | Main | A$0800-$0FFF | L$0800 | `desktop_main.s` |
| Invoker | B$012E80 | Main | A$0290-$03EF | L$0160 | `invoker.s` |
| Disk Copy 1/4 | B$012FE0 | Main | A$0800-$09FF | L$0200 | `ovl1.s` |
| Disk Copy 2/4 | B$0131E0 | Main | A$1800-$19FF | L$0200 | `ovl1a.s` |
@ -226,6 +226,14 @@ $0100 +-------------+ +-------------+
$0000 +-------------+ +-------------+
```
#### Disk Copy Overlay
The Disk Copy command replaces large chunks of memory and is best
thought of as a separate application. When exiting, the DeskTop is
restarted from the beginning.
thought of as a separate application.
The first part (`ovl1.s`) loads into main memory the other overlays,
but in turn it loads a second short ($200-byte) overlay (`ovl1a.s`).
This then loads a replacement for the resources in the aux language
card area (`ovl1b.s`) and another block of code in main memory
(`ovl1c.s`). When exiting, the DeskTop is restarted from the
beginning.