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L/+Belis2
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_28.ADF |
| Filename: | L/+Belis2 |
| Read OK: | ✔ |
| File size: | 13FE bytes |
| Load address: | 2B206576 |
| Exec address: | 696C6542 |
File contents
Reply to Rob Sprowson RE: Thrust Hardware Scrolling Routine
to everyone : Hacking Tips
Thanks for the tip in EUG26 Rob.
(For everyone's benefit) My objective is to save a memory dump of THRUST,
in order to extract routines for my own games etc..., especially the
hardware scrolling routine which THRUST uses - the screen scrolls by a
fixed amount when your ship reaches a set distance from the edge of the
screen.
I had the usual problems, in that as with most games, the author uses
EORing routines to make life difficult for hackers. In the case of
THRUST, there is more than one EORing routine, as well as the code and
data relocation routines. Previous attempts to decypher the code after
running one EORing routine have yielded mostly gibberish, so I was looking
for another method of getting the decoded game onto a disk.
Following Rob's tip in EUG26 of causing an IRQ by pulling the NIRQ pin
of the 1MHz bus low (by shorting pin 7 to pin 8 with a screwdriver) and
trapping the interrupt in a sideways RAM image with service call &05, I
have managed to save most of the game to disk in decoded form. (The parts
which remain are &D00 to &DFF - the NMI workspace - as I decided that
saving to tape was too laborious, being used to disk systems with instant
file access; and &700 to &780 - the CLI buffer - which is corrupted by
*SAVEing the contents of memory to disk). Attempts to *SAVE to memory
from the sideways RAM image failed. I shall save the missing bits later,
using a memory relocation routine in the sideways RAM image.
The machine configuration was as follows for the successful save:
Master 128 with double DSDD 5.25" drive.
Important *configure parameters: Mode 128 - important not to wipe
main memory when break is pressed.
File 9 - ADFS
No Directory
No Boot - autoboot would be a
nuisance.
The program THHACK was used to create a ROM image in sideways RAM which
would intercept the unrecognised interrupt and disable the wipe-on-break
function of *FX200,3. This program is on the disk.
The following is a record of what happened:
*FX151,78,127 disable all IRQs
<CTRL-BREAK> reset machine. Since the IRQs are disabled, the
machine is reset to its power-on state. This
technique will clear even the mysterious ROM-not-
found-even-when-it-wasn't-*UNPLUGged errors (see
later).
*DIR $.THRUST Move to ADFS directory containing THHACK and
THRUST.
CHAIN"THHACK" Run hacking program.
PRINT ~O% Get location of end of source code (O% is used on
e.g. 944 the Master series to enable code to be set to run
elsewhere in memory - in this case at &8000)
*SAVE THHACK? 900 945 8000 save the RAM image.
*SRLOAD THHACK? 8000 4 Q load RAM image into SWRAM bank 4.
<CTRL-BREAK> reset to ADFS, Mode 128 and install RAM image.
*DIR $.THRUST go to THRUST directory.
*THRUST run THRUST game.
lift computer, ready to interrupt the game.
short pins 7-8 of 1MHz bus with a screwdriver.
the machine locks up, as the error stack has filled
up, due to "switch bounce" on the 1MHz bus pins,
and has begun to overwrite the stack.
N.B. - I noticed that THRUST intercepts the IRQ1V
vector - if it had masked all the IRQs it didn't
use (by returning with RTI instead of exiting via
the old contents of the vector), then it might not
have permitted the MOS to pass the 1MHz bus
interrupt round the paged ROMs for the THHACK ROM
to intercept it.
<CTRL-BREAK> This is safe, as the ROM code has disabled the
wipe-on-break with *FX200,0
the machine is reset to mode 128 and BASIC, but
ADFS is nowhere to be found!
<CTRL-D-BREAK> Try DFS instead.
grab a DFS disk
*SAVE MEM 0 8000 Save memory to disk (no point saving mamory above
&8000 as it will contain the DFS ROM, workspace and
the MOS)
*SAVE MEM2 E00 8000 Save a block of memory which can be reloaded
(attempting to reload a file over MOS variables or
NMI workspace will cause a crash)
*DUMP MEM <CTRL-N> look through memory dump for messages such as
"Game over" or "Press space to start", and
note their locations in memory (in some games the
messages appear backwards - note the location of
the last letter or trailing null byte in this
case).
And so the process continues...
00000000 52 65 70 6c 79 20 74 6f 20 52 6f 62 20 53 70 72 |Reply to Rob Spr| 00000010 6f 77 73 6f 6e 20 52 45 3a 20 54 68 72 75 73 74 |owson RE: Thrust| 00000020 20 48 61 72 64 77 61 72 65 20 53 63 72 6f 6c 6c | Hardware Scroll| 00000030 69 6e 67 20 52 6f 75 74 69 6e 65 0d 20 20 20 20 |ing Routine. | 00000040 20 20 74 6f 20 65 76 65 72 79 6f 6e 65 20 3a 20 | to everyone : | 00000050 48 61 63 6b 69 6e 67 20 54 69 70 73 0d 0d 54 68 |Hacking Tips..Th| 00000060 61 6e 6b 73 20 66 6f 72 20 74 68 65 20 74 69 70 |anks for the tip| 00000070 20 69 6e 20 45 55 47 32 36 20 52 6f 62 2e 0d 0d | in EUG26 Rob...| 00000080 28 46 6f 72 20 65 76 65 72 79 6f 6e 65 27 73 20 |(For everyone's | 00000090 62 65 6e 65 66 69 74 29 20 4d 79 20 6f 62 6a 65 |benefit) My obje| 000000a0 63 74 69 76 65 20 69 73 20 74 6f 20 73 61 76 65 |ctive is to save| 000000b0 20 61 20 6d 65 6d 6f 72 79 20 64 75 6d 70 20 6f | a memory dump o| 000000c0 66 20 54 48 52 55 53 54 2c 0d 69 6e 20 6f 72 64 |f THRUST,.in ord| 000000d0 65 72 20 74 6f 20 65 78 74 72 61 63 74 20 72 6f |er to extract ro| 000000e0 75 74 69 6e 65 73 20 66 6f 72 20 6d 79 20 6f 77 |utines for my ow| 000000f0 6e 20 67 61 6d 65 73 20 65 74 63 2e 2e 2e 2c 20 |n games etc..., | 00000100 65 73 70 65 63 69 61 6c 6c 79 20 74 68 65 0d 68 |especially the.h| 00000110 61 72 64 77 61 72 65 20 73 63 72 6f 6c 6c 69 6e |ardware scrollin| 00000120 67 20 72 6f 75 74 69 6e 65 20 77 68 69 63 68 20 |g routine which | 00000130 54 48 52 55 53 54 20 75 73 65 73 20 2d 20 74 68 |THRUST uses - th| 00000140 65 20 73 63 72 65 65 6e 20 73 63 72 6f 6c 6c 73 |e screen scrolls| 00000150 20 62 79 20 61 0d 66 69 78 65 64 20 61 6d 6f 75 | by a.fixed amou| 00000160 6e 74 20 77 68 65 6e 20 79 6f 75 72 20 73 68 69 |nt when your shi| 00000170 70 20 72 65 61 63 68 65 73 20 61 20 73 65 74 20 |p reaches a set | 00000180 64 69 73 74 61 6e 63 65 20 66 72 6f 6d 20 74 68 |distance from th| 00000190 65 20 65 64 67 65 20 6f 66 20 74 68 65 0d 73 63 |e edge of the.sc| 000001a0 72 65 65 6e 2e 0d 0d 49 20 68 61 64 20 74 68 65 |reen...I had the| 000001b0 20 75 73 75 61 6c 20 70 72 6f 62 6c 65 6d 73 2c | usual problems,| 000001c0 20 69 6e 20 74 68 61 74 20 61 73 20 77 69 74 68 | in that as with| 000001d0 20 6d 6f 73 74 20 67 61 6d 65 73 2c 20 74 68 65 | most games, the| 000001e0 20 61 75 74 68 6f 72 20 75 73 65 73 0d 45 4f 52 | author uses.EOR| 000001f0 69 6e 67 20 72 6f 75 74 69 6e 65 73 20 74 6f 20 |ing routines to | 00000200 6d 61 6b 65 20 6c 69 66 65 20 64 69 66 66 69 63 |make life diffic| 00000210 75 6c 74 20 66 6f 72 20 68 61 63 6b 65 72 73 2e |ult for hackers.| 00000220 20 20 49 6e 20 74 68 65 20 63 61 73 65 20 6f 66 | In the case of| 00000230 0d 54 48 52 55 53 54 2c 20 74 68 65 72 65 20 69 |.THRUST, there i| 00000240 73 20 6d 6f 72 65 20 74 68 61 6e 20 6f 6e 65 20 |s more than one | 00000250 45 4f 52 69 6e 67 20 72 6f 75 74 69 6e 65 2c 20 |EORing routine, | 00000260 61 73 20 77 65 6c 6c 20 61 73 20 74 68 65 20 63 |as well as the c| 00000270 6f 64 65 20 61 6e 64 0d 64 61 74 61 20 72 65 6c |ode and.data rel| 00000280 6f 63 61 74 69 6f 6e 20 72 6f 75 74 69 6e 65 73 |ocation routines| 00000290 2e 20 20 50 72 65 76 69 6f 75 73 20 61 74 74 65 |. Previous atte| 000002a0 6d 70 74 73 20 74 6f 20 64 65 63 79 70 68 65 72 |mpts to decypher| 000002b0 20 74 68 65 20 63 6f 64 65 20 61 66 74 65 72 0d | the code after.| 000002c0 72 75 6e 6e 69 6e 67 20 6f 6e 65 20 45 4f 52 69 |running one EORi| 000002d0 6e 67 20 72 6f 75 74 69 6e 65 20 68 61 76 65 20 |ng routine have | 000002e0 79 69 65 6c 64 65 64 20 6d 6f 73 74 6c 79 20 67 |yielded mostly g| 000002f0 69 62 62 65 72 69 73 68 2c 20 73 6f 20 49 20 77 |ibberish, so I w| 00000300 61 73 20 6c 6f 6f 6b 69 6e 67 0d 66 6f 72 20 61 |as looking.for a| 00000310 6e 6f 74 68 65 72 20 6d 65 74 68 6f 64 20 6f 66 |nother method of| 00000320 20 67 65 74 74 69 6e 67 20 74 68 65 20 64 65 63 | getting the dec| 00000330 6f 64 65 64 20 67 61 6d 65 20 6f 6e 74 6f 20 61 |oded game onto a| 00000340 20 64 69 73 6b 2e 0d 0d 46 6f 6c 6c 6f 77 69 6e | disk...Followin| 00000350 67 20 52 6f 62 27 73 20 74 69 70 20 69 6e 20 45 |g Rob's tip in E| 00000360 55 47 32 36 20 6f 66 20 63 61 75 73 69 6e 67 20 |UG26 of causing | 00000370 61 6e 20 49 52 51 20 62 79 20 70 75 6c 6c 69 6e |an IRQ by pullin| 00000380 67 20 74 68 65 20 4e 49 52 51 20 70 69 6e 0d 6f |g the NIRQ pin.o| 00000390 66 20 74 68 65 20 31 4d 48 7a 20 62 75 73 20 6c |f the 1MHz bus l| 000003a0 6f 77 20 28 62 79 20 73 68 6f 72 74 69 6e 67 20 |ow (by shorting | 000003b0 70 69 6e 20 37 20 74 6f 20 70 69 6e 20 38 20 77 |pin 7 to pin 8 w| 000003c0 69 74 68 20 61 20 73 63 72 65 77 64 72 69 76 65 |ith a screwdrive| 000003d0 72 29 20 61 6e 64 0d 74 72 61 70 70 69 6e 67 20 |r) and.trapping | 000003e0 74 68 65 20 69 6e 74 65 72 72 75 70 74 20 69 6e |the interrupt in| 000003f0 20 61 20 73 69 64 65 77 61 79 73 20 52 41 4d 20 | a sideways RAM | 00000400 69 6d 61 67 65 20 77 69 74 68 20 73 65 72 76 69 |image with servi| 00000410 63 65 20 63 61 6c 6c 20 26 30 35 2c 20 49 0d 68 |ce call &05, I.h| 00000420 61 76 65 20 6d 61 6e 61 67 65 64 20 74 6f 20 73 |ave managed to s| 00000430 61 76 65 20 6d 6f 73 74 20 6f 66 20 74 68 65 20 |ave most of the | 00000440 67 61 6d 65 20 74 6f 20 64 69 73 6b 20 69 6e 20 |game to disk in | 00000450 64 65 63 6f 64 65 64 20 66 6f 72 6d 2e 20 28 54 |decoded form. (T| 00000460 68 65 20 70 61 72 74 73 0d 77 68 69 63 68 20 72 |he parts.which r| 00000470 65 6d 61 69 6e 20 61 72 65 20 26 44 30 30 20 74 |emain are &D00 t| 00000480 6f 20 26 44 46 46 20 2d 20 74 68 65 20 4e 4d 49 |o &DFF - the NMI| 00000490 20 77 6f 72 6b 73 70 61 63 65 20 2d 20 61 73 20 | workspace - as | 000004a0 49 20 64 65 63 69 64 65 64 20 74 68 61 74 0d 73 |I decided that.s| 000004b0 61 76 69 6e 67 20 74 6f 20 74 61 70 65 20 77 61 |aving to tape wa| 000004c0 73 20 74 6f 6f 20 6c 61 62 6f 72 69 6f 75 73 2c |s too laborious,| 000004d0 20 62 65 69 6e 67 20 75 73 65 64 20 74 6f 20 64 | being used to d| 000004e0 69 73 6b 20 73 79 73 74 65 6d 73 20 77 69 74 68 |isk systems with| 000004f0 20 69 6e 73 74 61 6e 74 0d 66 69 6c 65 20 61 63 | instant.file ac| 00000500 63 65 73 73 3b 20 61 6e 64 20 26 37 30 30 20 74 |cess; and &700 t| 00000510 6f 20 26 37 38 30 20 2d 20 74 68 65 20 43 4c 49 |o &780 - the CLI| 00000520 20 62 75 66 66 65 72 20 2d 20 77 68 69 63 68 20 | buffer - which | 00000530 69 73 20 63 6f 72 72 75 70 74 65 64 20 62 79 0d |is corrupted by.| 00000540 2a 53 41 56 45 69 6e 67 20 74 68 65 20 63 6f 6e |*SAVEing the con| 00000550 74 65 6e 74 73 20 6f 66 20 6d 65 6d 6f 72 79 20 |tents of memory | 00000560 74 6f 20 64 69 73 6b 29 2e 20 20 41 74 74 65 6d |to disk). Attem| 00000570 70 74 73 20 74 6f 20 2a 53 41 56 45 20 74 6f 20 |pts to *SAVE to | 00000580 6d 65 6d 6f 72 79 0d 66 72 6f 6d 20 74 68 65 20 |memory.from the | 00000590 73 69 64 65 77 61 79 73 20 52 41 4d 20 69 6d 61 |sideways RAM ima| 000005a0 67 65 20 66 61 69 6c 65 64 2e 20 20 49 20 73 68 |ge failed. I sh| 000005b0 61 6c 6c 20 73 61 76 65 20 74 68 65 20 6d 69 73 |all save the mis| 000005c0 73 69 6e 67 20 62 69 74 73 20 6c 61 74 65 72 2c |sing bits later,| 000005d0 0d 75 73 69 6e 67 20 61 20 6d 65 6d 6f 72 79 20 |.using a memory | 000005e0 72 65 6c 6f 63 61 74 69 6f 6e 20 72 6f 75 74 69 |relocation routi| 000005f0 6e 65 20 69 6e 20 74 68 65 20 73 69 64 65 77 61 |ne in the sidewa| 00000600 79 73 20 52 41 4d 20 69 6d 61 67 65 2e 0d 0d 54 |ys RAM image...T| 00000610 68 65 20 6d 61 63 68 69 6e 65 20 63 6f 6e 66 69 |he machine confi| 00000620 67 75 72 61 74 69 6f 6e 20 77 61 73 20 61 73 20 |guration was as | 00000630 66 6f 6c 6c 6f 77 73 20 66 6f 72 20 74 68 65 20 |follows for the | 00000640 73 75 63 63 65 73 73 66 75 6c 20 73 61 76 65 3a |successful save:| 00000650 0d 0d 4d 61 73 74 65 72 20 31 32 38 20 77 69 74 |..Master 128 wit| 00000660 68 20 64 6f 75 62 6c 65 20 44 53 44 44 20 35 2e |h double DSDD 5.| 00000670 32 35 22 20 64 72 69 76 65 2e 0d 49 6d 70 6f 72 |25" drive..Impor| 00000680 74 61 6e 74 20 2a 63 6f 6e 66 69 67 75 72 65 20 |tant *configure | 00000690 70 61 72 61 6d 65 74 65 72 73 3a 20 20 20 4d 6f |parameters: Mo| 000006a0 64 65 20 31 32 38 20 2d 20 69 6d 70 6f 72 74 61 |de 128 - importa| 000006b0 6e 74 20 6e 6f 74 20 74 6f 20 77 69 70 65 0d 20 |nt not to wipe. | 000006c0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | * 000006e0 20 20 6d 61 69 6e 20 6d 65 6d 6f 72 79 20 77 68 | main memory wh| 000006f0 65 6e 20 62 72 65 61 6b 20 69 73 20 70 72 65 73 |en break is pres| 00000700 73 65 64 2e 0d 20 20 20 20 20 20 20 20 20 20 20 |sed.. | 00000710 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000720 20 20 20 20 20 20 20 20 46 69 6c 65 20 39 20 2d | File 9 -| 00000730 20 41 44 46 53 0d 20 20 20 20 20 20 20 20 20 20 | ADFS. | 00000740 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000750 20 20 20 20 20 20 20 20 20 4e 6f 20 44 69 72 65 | No Dire| 00000760 63 74 6f 72 79 0d 20 20 20 20 20 20 20 20 20 20 |ctory. | 00000770 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000780 20 20 20 20 20 20 20 20 20 4e 6f 20 42 6f 6f 74 | No Boot| 00000790 20 2d 20 61 75 74 6f 62 6f 6f 74 20 77 6f 75 6c | - autoboot woul| 000007a0 64 20 62 65 20 61 0d 20 20 20 20 20 20 20 20 20 |d be a. | 000007b0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 000007c0 20 20 20 20 20 20 20 20 20 20 6e 75 69 73 61 6e | nuisan| 000007d0 63 65 2e 0d 0d 54 68 65 20 70 72 6f 67 72 61 6d |ce...The program| 000007e0 20 54 48 48 41 43 4b 20 77 61 73 20 75 73 65 64 | THHACK was used| 000007f0 20 74 6f 20 63 72 65 61 74 65 20 61 20 52 4f 4d | to create a ROM| 00000800 20 69 6d 61 67 65 20 69 6e 20 73 69 64 65 77 61 | image in sidewa| 00000810 79 73 20 52 41 4d 20 77 68 69 63 68 0d 77 6f 75 |ys RAM which.wou| 00000820 6c 64 20 69 6e 74 65 72 63 65 70 74 20 74 68 65 |ld intercept the| 00000830 20 75 6e 72 65 63 6f 67 6e 69 73 65 64 20 69 6e | unrecognised in| 00000840 74 65 72 72 75 70 74 20 61 6e 64 20 64 69 73 61 |terrupt and disa| 00000850 62 6c 65 20 74 68 65 20 77 69 70 65 2d 6f 6e 2d |ble the wipe-on-| 00000860 62 72 65 61 6b 0d 66 75 6e 63 74 69 6f 6e 20 6f |break.function o| 00000870 66 20 2a 46 58 32 30 30 2c 33 2e 20 20 54 68 69 |f *FX200,3. Thi| 00000880 73 20 70 72 6f 67 72 61 6d 20 69 73 20 6f 6e 20 |s program is on | 00000890 74 68 65 20 64 69 73 6b 2e 0d 0d 54 68 65 20 66 |the disk...The f| 000008a0 6f 6c 6c 6f 77 69 6e 67 20 69 73 20 61 20 72 65 |ollowing is a re| 000008b0 63 6f 72 64 20 6f 66 20 77 68 61 74 20 68 61 70 |cord of what hap| 000008c0 70 65 6e 65 64 3a 0d 0d 2a 46 58 31 35 31 2c 37 |pened:..*FX151,7| 000008d0 38 2c 31 32 37 20 20 20 20 20 20 20 20 20 20 64 |8,127 d| 000008e0 69 73 61 62 6c 65 20 61 6c 6c 20 49 52 51 73 0d |isable all IRQs.| 000008f0 0d 3c 43 54 52 4c 2d 42 52 45 41 4b 3e 20 20 20 |.<CTRL-BREAK> | 00000900 20 20 20 20 20 20 20 20 72 65 73 65 74 20 6d 61 | reset ma| 00000910 63 68 69 6e 65 2e 20 20 53 69 6e 63 65 20 74 68 |chine. Since th| 00000920 65 20 49 52 51 73 20 61 72 65 20 64 69 73 61 62 |e IRQs are disab| 00000930 6c 65 64 2c 20 74 68 65 0d 20 20 20 20 20 20 20 |led, the. | 00000940 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000950 6d 61 63 68 69 6e 65 20 69 73 20 72 65 73 65 74 |machine is reset| 00000960 20 74 6f 20 69 74 73 20 70 6f 77 65 72 2d 6f 6e | to its power-on| 00000970 20 73 74 61 74 65 2e 20 20 54 68 69 73 0d 20 20 | state. This. | 00000980 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000990 20 20 20 20 20 74 65 63 68 6e 69 71 75 65 20 77 | technique w| 000009a0 69 6c 6c 20 63 6c 65 61 72 20 65 76 65 6e 20 74 |ill clear even t| 000009b0 68 65 20 6d 79 73 74 65 72 69 6f 75 73 20 52 4f |he mysterious RO| 000009c0 4d 2d 6e 6f 74 2d 0d 20 20 20 20 20 20 20 20 20 |M-not-. | 000009d0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 66 6f | fo| 000009e0 75 6e 64 2d 65 76 65 6e 2d 77 68 65 6e 2d 69 74 |und-even-when-it| 000009f0 2d 77 61 73 6e 27 74 2d 2a 55 4e 50 4c 55 47 67 |-wasn't-*UNPLUGg| 00000a00 65 64 20 65 72 72 6f 72 73 20 28 73 65 65 0d 20 |ed errors (see. | 00000a10 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000a20 20 20 20 20 20 20 6c 61 74 65 72 29 2e 0d 0d 2a | later)...*| 00000a30 44 49 52 20 24 2e 54 48 52 55 53 54 20 20 20 20 |DIR $.THRUST | 00000a40 20 20 20 20 20 20 4d 6f 76 65 20 74 6f 20 41 44 | Move to AD| 00000a50 46 53 20 64 69 72 65 63 74 6f 72 79 20 63 6f 6e |FS directory con| 00000a60 74 61 69 6e 69 6e 67 20 54 48 48 41 43 4b 20 61 |taining THHACK a| 00000a70 6e 64 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 |nd. | 00000a80 20 20 20 20 20 20 20 20 20 20 54 48 52 55 53 54 | THRUST| 00000a90 2e 0d 0d 43 48 41 49 4e 22 54 48 48 41 43 4b 22 |...CHAIN"THHACK"| 00000aa0 20 20 20 20 20 20 20 20 20 20 52 75 6e 20 68 61 | Run ha| 00000ab0 63 6b 69 6e 67 20 70 72 6f 67 72 61 6d 2e 0d 0d |cking program...| 00000ac0 50 52 49 4e 54 20 7e 4f 25 20 20 20 20 20 20 20 |PRINT ~O% | 00000ad0 20 20 20 20 20 20 20 47 65 74 20 6c 6f 63 61 74 | Get locat| 00000ae0 69 6f 6e 20 6f 66 20 65 6e 64 20 6f 66 20 73 6f |ion of end of so| 00000af0 75 72 63 65 20 63 6f 64 65 20 28 4f 25 20 69 73 |urce code (O% is| 00000b00 20 75 73 65 64 20 6f 6e 0d 65 2e 67 2e 20 39 34 | used on.e.g. 94| 00000b10 34 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |4 | 00000b20 74 68 65 20 4d 61 73 74 65 72 20 73 65 72 69 65 |the Master serie| 00000b30 73 20 74 6f 20 65 6e 61 62 6c 65 20 63 6f 64 65 |s to enable code| 00000b40 20 74 6f 20 62 65 20 73 65 74 20 74 6f 20 72 75 | to be set to ru| 00000b50 6e 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |n. | 00000b60 20 20 20 20 20 20 20 20 20 65 6c 73 65 77 68 65 | elsewhe| 00000b70 72 65 20 69 6e 20 6d 65 6d 6f 72 79 20 2d 20 69 |re in memory - i| 00000b80 6e 20 74 68 69 73 20 63 61 73 65 20 61 74 20 26 |n this case at &| 00000b90 38 30 30 30 29 0d 0d 2a 53 41 56 45 20 54 48 48 |8000)..*SAVE THH| 00000ba0 41 43 4b 3f 20 39 30 30 20 39 34 35 20 38 30 30 |ACK? 900 945 800| 00000bb0 30 20 20 20 20 20 73 61 76 65 20 74 68 65 20 52 |0 save the R| 00000bc0 41 4d 20 69 6d 61 67 65 2e 0d 0d 2a 53 52 4c 4f |AM image...*SRLO| 00000bd0 41 44 20 54 48 48 41 43 4b 3f 20 38 30 30 30 20 |AD THHACK? 8000 | 00000be0 34 20 51 20 20 20 20 20 20 20 6c 6f 61 64 20 52 |4 Q load R| 00000bf0 41 4d 20 69 6d 61 67 65 20 69 6e 74 6f 20 53 57 |AM image into SW| 00000c00 52 41 4d 20 62 61 6e 6b 20 34 2e 0d 0d 3c 43 54 |RAM bank 4...<CT| 00000c10 52 4c 2d 42 52 45 41 4b 3e 20 20 20 20 20 20 20 |RL-BREAK> | 00000c20 20 20 20 20 72 65 73 65 74 20 74 6f 20 41 44 46 | reset to ADF| 00000c30 53 2c 20 4d 6f 64 65 20 31 32 38 20 61 6e 64 20 |S, Mode 128 and | 00000c40 69 6e 73 74 61 6c 6c 20 52 41 4d 20 69 6d 61 67 |install RAM imag| 00000c50 65 2e 0d 0d 2a 44 49 52 20 24 2e 54 48 52 55 53 |e...*DIR $.THRUS| 00000c60 54 20 20 20 20 20 20 20 20 20 20 67 6f 20 74 6f |T go to| 00000c70 20 54 48 52 55 53 54 20 64 69 72 65 63 74 6f 72 | THRUST director| 00000c80 79 2e 0d 0d 2a 54 48 52 55 53 54 20 20 20 20 20 |y...*THRUST | 00000c90 20 20 20 20 20 20 20 20 20 20 20 72 75 6e 20 54 | run T| 00000ca0 48 52 55 53 54 20 67 61 6d 65 2e 0d 0d 6c 69 66 |HRUST game...lif| 00000cb0 74 20 63 6f 6d 70 75 74 65 72 2c 20 72 65 61 64 |t computer, read| 00000cc0 79 20 74 6f 20 69 6e 74 65 72 72 75 70 74 20 74 |y to interrupt t| 00000cd0 68 65 20 67 61 6d 65 2e 0d 0d 73 68 6f 72 74 20 |he game...short | 00000ce0 70 69 6e 73 20 37 2d 38 20 6f 66 20 31 4d 48 7a |pins 7-8 of 1MHz| 00000cf0 20 62 75 73 20 77 69 74 68 20 61 20 73 63 72 65 | bus with a scre| 00000d00 77 64 72 69 76 65 72 2e 0d 0d 20 20 20 20 20 20 |wdriver... | 00000d10 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000d20 20 74 68 65 20 6d 61 63 68 69 6e 65 20 6c 6f 63 | the machine loc| 00000d30 6b 73 20 75 70 2c 20 61 73 20 74 68 65 20 65 72 |ks up, as the er| 00000d40 72 6f 72 20 73 74 61 63 6b 20 68 61 73 20 66 69 |ror stack has fi| 00000d50 6c 6c 65 64 0d 20 20 20 20 20 20 20 20 20 20 20 |lled. | 00000d60 20 20 20 20 20 20 20 20 20 20 20 20 75 70 2c 20 | up, | 00000d70 64 75 65 20 74 6f 20 22 73 77 69 74 63 68 20 62 |due to "switch b| 00000d80 6f 75 6e 63 65 22 20 6f 6e 20 74 68 65 20 31 4d |ounce" on the 1M| 00000d90 48 7a 20 62 75 73 20 70 69 6e 73 2c 0d 20 20 20 |Hz bus pins,. | 00000da0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000db0 20 20 20 20 61 6e 64 20 68 61 73 20 62 65 67 75 | and has begu| 00000dc0 6e 20 74 6f 20 6f 76 65 72 77 72 69 74 65 20 74 |n to overwrite t| 00000dd0 68 65 20 73 74 61 63 6b 2e 0d 0d 20 20 20 20 20 |he stack... | 00000de0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000df0 20 20 4e 2e 42 2e 20 2d 20 49 20 6e 6f 74 69 63 | N.B. - I notic| 00000e00 65 64 20 74 68 61 74 20 54 48 52 55 53 54 20 69 |ed that THRUST i| 00000e10 6e 74 65 72 63 65 70 74 73 20 74 68 65 20 49 52 |ntercepts the IR| 00000e20 51 31 56 0d 20 20 20 20 20 20 20 20 20 20 20 20 |Q1V. | 00000e30 20 20 20 20 20 20 20 20 20 20 20 76 65 63 74 6f | vecto| 00000e40 72 20 2d 20 69 66 20 69 74 20 68 61 64 20 6d 61 |r - if it had ma| 00000e50 73 6b 65 64 20 61 6c 6c 20 74 68 65 20 49 52 51 |sked all the IRQ| 00000e60 73 20 69 74 20 64 69 64 6e 27 74 0d 20 20 20 20 |s it didn't. | 00000e70 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000e80 20 20 20 75 73 65 20 28 62 79 20 72 65 74 75 72 | use (by retur| 00000e90 6e 69 6e 67 20 77 69 74 68 20 52 54 49 20 69 6e |ning with RTI in| 00000ea0 73 74 65 61 64 20 6f 66 20 65 78 69 74 69 6e 67 |stead of exiting| 00000eb0 20 76 69 61 0d 20 20 20 20 20 20 20 20 20 20 20 | via. | 00000ec0 20 20 20 20 20 20 20 20 20 20 20 20 74 68 65 20 | the | 00000ed0 6f 6c 64 20 63 6f 6e 74 65 6e 74 73 20 6f 66 20 |old contents of | 00000ee0 74 68 65 20 76 65 63 74 6f 72 29 2c 20 74 68 65 |the vector), the| 00000ef0 6e 20 69 74 20 6d 69 67 68 74 20 6e 6f 74 0d 20 |n it might not. | 00000f00 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000f10 20 20 20 20 20 20 68 61 76 65 20 70 65 72 6d 69 | have permi| 00000f20 74 74 65 64 20 74 68 65 20 4d 4f 53 20 74 6f 20 |tted the MOS to | 00000f30 70 61 73 73 20 74 68 65 20 31 4d 48 7a 20 62 75 |pass the 1MHz bu| 00000f40 73 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |s. | 00000f50 20 20 20 20 20 20 20 20 20 69 6e 74 65 72 72 75 | interru| 00000f60 70 74 20 72 6f 75 6e 64 20 74 68 65 20 70 61 67 |pt round the pag| 00000f70 65 64 20 52 4f 4d 73 20 66 6f 72 20 74 68 65 20 |ed ROMs for the | 00000f80 54 48 48 41 43 4b 20 52 4f 4d 0d 20 20 20 20 20 |THHACK ROM. | 00000f90 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000fa0 20 20 74 6f 20 69 6e 74 65 72 63 65 70 74 20 69 | to intercept i| 00000fb0 74 2e 0d 0d 3c 43 54 52 4c 2d 42 52 45 41 4b 3e |t...<CTRL-BREAK>| 00000fc0 20 20 20 20 20 20 20 20 20 20 20 54 68 69 73 20 | This | 00000fd0 69 73 20 73 61 66 65 2c 20 61 73 20 74 68 65 20 |is safe, as the | 00000fe0 52 4f 4d 20 63 6f 64 65 20 68 61 73 20 64 69 73 |ROM code has dis| 00000ff0 61 62 6c 65 64 20 74 68 65 0d 20 20 20 20 20 20 |abled the. | 00001000 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00001010 20 77 69 70 65 2d 6f 6e 2d 62 72 65 61 6b 20 77 | wipe-on-break w| 00001020 69 74 68 20 2a 46 58 32 30 30 2c 30 0d 0d 20 20 |ith *FX200,0.. | 00001030 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00001040 20 20 20 20 20 74 68 65 20 6d 61 63 68 69 6e 65 | the machine| 00001050 20 69 73 20 72 65 73 65 74 20 74 6f 20 6d 6f 64 | is reset to mod| 00001060 65 20 31 32 38 20 61 6e 64 20 42 41 53 49 43 2c |e 128 and BASIC,| 00001070 20 62 75 74 0d 20 20 20 20 20 20 20 20 20 20 20 | but. | 00001080 20 20 20 20 20 20 20 20 20 20 20 20 41 44 46 53 | ADFS| 00001090 20 69 73 20 6e 6f 77 68 65 72 65 20 74 6f 20 62 | is nowhere to b| 000010a0 65 20 66 6f 75 6e 64 21 0d 0d 3c 43 54 52 4c 2d |e found!..<CTRL-| 000010b0 44 2d 42 52 45 41 4b 3e 20 20 20 20 20 20 20 20 |D-BREAK> | 000010c0 20 54 72 79 20 44 46 53 20 69 6e 73 74 65 61 64 | Try DFS instead| 000010d0 2e 0d 0d 67 72 61 62 20 61 20 44 46 53 20 64 69 |...grab a DFS di| 000010e0 73 6b 0d 0d 2a 53 41 56 45 20 4d 45 4d 20 30 20 |sk..*SAVE MEM 0 | 000010f0 38 30 30 30 20 20 20 20 20 20 20 53 61 76 65 20 |8000 Save | 00001100 6d 65 6d 6f 72 79 20 74 6f 20 64 69 73 6b 20 28 |memory to disk (| 00001110 6e 6f 20 70 6f 69 6e 74 20 73 61 76 69 6e 67 20 |no point saving | 00001120 6d 61 6d 6f 72 79 20 61 62 6f 76 65 0d 20 20 20 |mamory above. | 00001130 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00001140 20 20 20 20 26 38 30 30 30 20 61 73 20 69 74 20 | &8000 as it | 00001150 77 69 6c 6c 20 63 6f 6e 74 61 69 6e 20 74 68 65 |will contain the| 00001160 20 44 46 53 20 52 4f 4d 2c 20 77 6f 72 6b 73 70 | DFS ROM, worksp| 00001170 61 63 65 20 61 6e 64 0d 20 20 20 20 20 20 20 20 |ace and. | 00001180 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 74 | t| 00001190 68 65 20 4d 4f 53 29 0d 0d 2a 53 41 56 45 20 4d |he MOS)..*SAVE M| 000011a0 45 4d 32 20 45 30 30 20 38 30 30 30 20 20 20 20 |EM2 E00 8000 | 000011b0 53 61 76 65 20 61 20 62 6c 6f 63 6b 20 6f 66 20 |Save a block of | 000011c0 6d 65 6d 6f 72 79 20 77 68 69 63 68 20 63 61 6e |memory which can| 000011d0 20 62 65 20 72 65 6c 6f 61 64 65 64 0d 20 20 20 | be reloaded. | 000011e0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 000011f0 20 20 20 20 28 61 74 74 65 6d 70 74 69 6e 67 20 | (attempting | 00001200 74 6f 20 72 65 6c 6f 61 64 20 61 20 66 69 6c 65 |to reload a file| 00001210 20 6f 76 65 72 20 4d 4f 53 20 76 61 72 69 61 62 | over MOS variab| 00001220 6c 65 73 20 6f 72 0d 20 20 20 20 20 20 20 20 20 |les or. | 00001230 20 20 20 20 20 20 20 20 20 20 20 20 20 20 4e 4d | NM| 00001240 49 20 77 6f 72 6b 73 70 61 63 65 20 77 69 6c 6c |I workspace will| 00001250 20 63 61 75 73 65 20 61 20 63 72 61 73 68 29 0d | cause a crash).| 00001260 0d 2a 44 55 4d 50 20 4d 45 4d 20 3c 43 54 52 4c |.*DUMP MEM <CTRL| 00001270 2d 4e 3e 20 20 20 20 20 6c 6f 6f 6b 20 74 68 72 |-N> look thr| 00001280 6f 75 67 68 20 6d 65 6d 6f 72 79 20 64 75 6d 70 |ough memory dump| 00001290 20 66 6f 72 20 6d 65 73 73 61 67 65 73 20 73 75 | for messages su| 000012a0 63 68 20 61 73 0d 20 20 20 20 20 20 20 20 20 20 |ch as. | 000012b0 20 20 20 20 20 20 20 20 20 20 20 20 20 22 47 61 | "Ga| 000012c0 6d 65 20 6f 76 65 72 22 20 6f 72 20 22 50 72 65 |me over" or "Pre| 000012d0 73 73 20 73 70 61 63 65 20 74 6f 20 73 74 61 72 |ss space to star| 000012e0 74 22 2c 20 61 6e 64 0d 20 20 20 20 20 20 20 20 |t", and. | 000012f0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 6e | n| 00001300 6f 74 65 20 74 68 65 69 72 20 6c 6f 63 61 74 69 |ote their locati| 00001310 6f 6e 73 20 69 6e 20 6d 65 6d 6f 72 79 20 28 69 |ons in memory (i| 00001320 6e 20 73 6f 6d 65 20 67 61 6d 65 73 20 74 68 65 |n some games the| 00001330 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |. | 00001340 20 20 20 20 20 20 20 20 6d 65 73 73 61 67 65 73 | messages| 00001350 20 61 70 70 65 61 72 20 62 61 63 6b 77 61 72 64 | appear backward| 00001360 73 20 2d 20 6e 6f 74 65 20 74 68 65 20 6c 6f 63 |s - note the loc| 00001370 61 74 69 6f 6e 20 6f 66 0d 20 20 20 20 20 20 20 |ation of. | 00001380 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00001390 74 68 65 20 6c 61 73 74 20 6c 65 74 74 65 72 20 |the last letter | 000013a0 6f 72 20 74 72 61 69 6c 69 6e 67 20 6e 75 6c 6c |or trailing null| 000013b0 20 62 79 74 65 20 69 6e 20 74 68 69 73 0d 20 20 | byte in this. | 000013c0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 000013d0 20 20 20 20 20 63 61 73 65 29 2e 0d 0d 41 6e 64 | case)...And| 000013e0 20 73 6f 20 74 68 65 20 70 72 6f 63 65 73 73 20 | so the process | 000013f0 63 6f 6e 74 69 6e 75 65 73 2e 2e 2e 0d 0d |continues.....| 000013fe
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.