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How to run the Dragon at double speed
Posted: Fri Dec 03, 2010 4:08 pm
by zephyr
The double speed pokes are explained here for people who are new to the Tandy CoCo, and Dragon computers.
POKE65495,0 or POKE&HFFD7,0 - Double speed for all code in ROM (BASIC/Cartridge), and I/O operations.
POKE65494,0 or POKE&HFFD6,0 - Resets to normal speed.
POKE65497,0 or POKE&HFFD9,0 - Double speed for all code in RAM, ROM, and I/O operations. Unfortunately, the hardware RAM refresh, and video display are disabled in this mode.
POKE65496,0 or POKE&HFFD8,0 - Resets to normal, or if you have previouly used POKE65495,0, it will return to that mode.
Notes:
1. Due mainly to the fitting of poor quality ROM and/or RAM chips, some Dragons will crash when these pokes are used.
2. If you accidentally save a cassette program in 65495 mode, you can only load it back in 65497 mode.
Re: How to run the Dragon at double speed
Posted: Sat Dec 04, 2010 4:30 pm
by prime
These of course also work on the CoCo 1 and 2 not sure about the CoCo 3.
Pressing reset will also cancel them and return the machine to it's default slow mode.
Phill.
Re: How to run the Dragon at double speed
Posted: Sun Dec 05, 2010 12:14 am
by zephyr
The CoCo 3 is designed to work in 65497 mode with fully operational RAM refresh, and video display. I could be wrong, but I don't think POKE65495 would work, because the BASIC operating system is copied to RAM at startup.
EDIT: It has now been confirmed that POKE65495,0 has no effect on the CoCo 3. The same applies even when operating in ROM (MAP 0) mode. My thanks to Ciaran Anscomb (sixxie) for testing POKE65495,0 on his real CoCo 3.
Re: How to run the Dragon at double speed
Posted: Fri May 11, 2012 3:12 pm
by zephyr
Listed below are some of the programs I like to use for testing Dragons and CoCos at double speed:
This should run OK on any Dragon that can handle the double speed (POKE65497,0) poke.
Code: Select all
POKE65495,0:POKE65497,0:PLAY"C":POKE65496,0:POKE65494,0
This will also run OK on most Dragon's.
Code: Select all
POKE65495,0:POKE65497,0:PLAY"CDE":POKE65496,0:POKE65494,0
The code listed from here-on gets progressively tougher and will run OK only on selected Dragons.
Code: Select all
POKE65495,0:POKE65497,0:PLAY"CDEFGAB":POKE65496,0:POKE65494,0
Code: Select all
POKE65495,0:POKE65497,0:SOUND1,50:POKE65496,0:POKE65494,0
Code: Select all
POKE65495,0:POKE65497,0:SOUND1,100:POKE65496,0:POKE65494,0
Code: Select all
POKE65495,0:POKE65497,0:SOUND1,150:POKE65496,0:POKE65494,0
Code: Select all
POKE65495,0:POKE65497,0:SOUND1,200:POKE65496,0:POKE65494,0
You can consider your Dragon to be pretty much bullet-proof if it survives this one without crashing.
Code: Select all
POKE65495,0:POKE65497,0:SOUND1,255:POKE65496,0:POKE65494,0
I like to use the following code for testing the durability of Dragons and CoCos at double speed over long periods.
Code: Select all
10 POKE65495,0
20 POKE65497,0:FOR I=0 TO 32767:X=PEEK(I):NEXT:POKE65496,0
30 FOR I=1 TO 500:IF INKEY$<>"Q" THEN NEXT:GOTO20
40 POKE65494,0
Re: How to run the Dragon at double speed
Posted: Fri May 11, 2012 3:26 pm
by zephyr
If you have a Dragon that won't handle the
double speed pokes, try replacing the 6809E processor with a Hitachi HD68B09E, HD63B09E or HD63C09E. If that doesn't fix the problem, replace the two BASIC ROMs (IC17 and IC18). If the BASIC ROMs you fitted are undamaged and of decent spec, you should now own a Dragon that can handle the address dependent double speed (POKE65495,0) mode. If you have decent spec RAM fitted, it should also be able to handle true double speed (POKE65497,0) mode.
Brand new HD68BO9E CPU's can currently be picked-up for less than five pounds via eBay. Also, look out for a cheap Dragon advertised for "Spares or Repair" on aBay to salvage the BASIC ROMs.
Re: How to run the Dragon at double speed
Posted: Tue May 15, 2012 11:45 pm
by Alastair
Steve, you should add that you need to let the Dragon warm up first, say half-an-hour. My anything but bullet-proof Dragon passes the POKE65495,0:POKE65497,0:SOUND1,255:POKE65496,0:POKE65494,0 test when cold
Re: How to run the Dragon at double speed
Posted: Wed May 16, 2012 12:53 am
by zephyr
Alastair wrote:Steve, you should add that you need to let the Dragon warm up first, say half-an-hour. My anything but bullet-proof Dragon passes the POKE65495,0:POKE65497,0:SOUND1,255:POKE65496,0:POKE65494,0 test when cold
Yes, I forgot to mention about allowing the Dragon to warm-up first. Thanks Alastair!
Re: How to run the Dragon at double speed
Posted: Thu Jan 03, 2013 2:48 am
by JCCyC
zephyr wrote:Brand new HD68BO9E CPU's
Whoa, whoa! Is THERE such a thing? Somebody is actually making 6809's in this day and age?? Which manufacturer???
Re: How to run the Dragon at double speed
Posted: Thu Jan 03, 2013 6:26 am
by zephyr
Re: How to run the Dragon at double speed
Posted: Thu Jan 03, 2013 11:10 am
by Dantyr
Nice!
Tested on the Color64 and follow the results:
POKE65495,0:POKE65497,0:PLAY"C":POKE65496,0:POKE65494,0 : Ok
POKE65495,0:POKE65497,0:PLAY"CDE":POKE65496,0:POKE65494,0 : OK
POKE65495,0:POKE65497,0:PLAY"CDEFGAB":POKE65496,0:POKE65494,0 : Come back, but the screen get poluted o some places with some strange characters.
POKE65495,0:POKE65497,0:SOUND1,50":POKE65496,0:POKE65494,0 : Come back, but the screen get poluted o some places with some strange characters.
POKE65495,0:POKE65497,0:SOUND1,100":POKE65496,0:POKE65494,0 : Screen garbled after execution have finished.
.
.
.
POKE65495,0:POKE65497,0:SOUND1,255":POKE65496,0:POKE65494,0 : Screen garbled after execution have finished.
Have yet to test on the Dragon.
Daniel