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THE GRAFIX MENU COLORS For a complete description of the COLORS option see the COLOR SCREEN section. BORDERS KEY SEQUENCE: None The BORDERS menu option allows you to toggle the C64's borders on and off. Because the Amiga does not support a true border around its screen, a border around the entire C64 screen can not be emulated efficiently. To support programs that need borders, for such things as changing the border color to signify some status within the program, A64 supports a border on the top and bottom of the screen. Changing the status of the borders will have no effect on the operation of A64, but may make some programs look better. The BORDERS menu option has two settings: ON and OFF. You can select one or the other of these settings and selecting one automatically unselects the other. The current selected setting is shown by displaying a checkmark next to it. When ON is selected A64 will display a border at the top and bottom of the C64 screen. When OFF is selected there will be no visible border on the C64 screen. NOTE: The borders will not be visible until you exit A64 Prefs to C64 mode. SCRN REFRESH KEY SEQUENCE: None The SCRN REFRESH menu option allows to change the way and speed in which A64 draws the C64 screen. When selecting SCRN REFRESH you will be prompted with a requester containing several gadgets. The function of each gadget is as follows: 3-18 SCREEN REFRESH TYPE GADGET A64 is capable of drawing the screen in two distinct ways and the SCREEN REFRESH TYPE GADGET allows you to switch between these two methods. This gadget has two settings: DIRECT and SAMPLE. Selecting DIRECT will force A64 to use DIRECT MODE and selecting SAMPLE will force A64 to use SAMPLE MODE. The meaning of each setting is as follows: DIRECT MODE When A64 is in DIRECT MODE it writes to the Amiga's screen directly. This means, when the C64 is performing an operation that changes some part of the C64's screen A64 make the same change immediately to the Amiga's screen. This way of drawing directly to the Amiga's screen has the advantage of showing changes of the C64's screen immediately resulting in smoother screen updates, but has the disadvantage of having the tendency to slow down A64 when alot of changes are happening to the C64's screen seemingly at one time. For example, scrolling in games. DIRECT MODE is the default setting for the way A64 draws the screen and it is suggested that you try using this setting before trying SAMPLE mode for most C64 programs. SAMPLE MODE When A64 is in SAMPLE MODE it draws the changes in the C64 screen at a set SAMPLE rate. This means that A64 will sample the C64 graphics at a certain rate to see what has changed and then draw the changes. This way of drawing the screen has the advantage of being faster when alot of changes are happening to the C64's screen seemingly at one time. For example, scrolling in games, but has the disadvantage of making the screen updates appear jerky and at times out of sequence. NOTE: Out of the two ways of drawing the screen, SAMPLE MODE is the most compatible with the C64. It has the ability to handle up to 25 raster IRQs per screen, spaced as little as 1 scan line apart, while DIRECT MODE can handle up to 25 raster IRQs per screen, spaced as little as 8 scan lines apart. Although DIRECT MODE has this limitation, it will handle most C64 programs with no problems, but if you do encounter a C64 program where the screen does not look like it should try switching to SAMPLE MODE to correct it. 3-19 SCREEN REFRESH RATE GADGET The SCREEN REFRESH RATE GADGET allows you to change the rate in which A64 checks if it should redraw the C64 screen. This gadget is a string gadget and it allows you to enter a five digit number that corresponds to A64's screen refresh rate. This number can range from 1-65535 and the way A64 interprets it is as follows: A64 uses the SCREEN REFRESH RATE value as a countdown to check if it should redraw the screen. A64 subtracts 1 from this value 60 times per second and when the value counts down to 0 A64 resets the counter and checks if it should redraw the screen. Depending on whether SAMPLE MODE or DIRECT MODE is selected and on what changes the C64 has made to its screen A64 will decide whether or not to redraw the screen. For example if you set this setting to 1 then A64 would subtract 1 from it 60 times per second (1-1=0) and would result in A64 checking if it should redraw the screen 60 times per second. See: REFRESH RATE TABLE in the GRAFIX section. OK AND CANCEL GADGETS Selecting OK will preserve all changes to the SCRN REFRESH settings and selecting CANCEL will ignore any changes and abort the operation. NOTE: Both the SCREEN REFRESH TYPE and SCREEN REFRESH RATE settings can have major effects on A64's speed. We suggest you play around with these settings while using different C64 programs to see their effects. RASTERS KEY SEQUENCE: None The RASTERS menu option allows you to change some settings related to the video scan line. When selecting RASTERS you will prompted with a requester containing several gadgets. The function of each gadget is as follows: SCAN LINE READ GADGET Before explaining this setting we need to explain some basic principals of video circuitry and how the C64 uses them. Inside your computer's monitor (or TV) is an electron beam that sweeps 3-20 across the inside of your monitor's picture tube, refreshing the picture as it goes. This electron beam sweeps across the screen from left to right and refreshes the screen one horizontal line at a time. This horizontal line is called a scan line. The standard NTSC screen is made up of 262 of these scan lines. This process of refreshing the screen, one scan line at time, happens very rapidly. It takes your monitor 1/60th of a second to refresh one entire screen. This means that in one second the screen will have been refreshed 60 times. Inside the C64 is a pair of registers (memory locations) that contain the current scan line number that is being refreshed by the monitor. These registers are used by MANY C64 programs for a variety of purposes. Seeing how these registers change at a regular rate many C64 programs use them for timing. Another popular use for these registers is for a program to wait for a specific scan line before continuing. A64 is capable of handling reads of the scan line registers in two ways and the SCAN LINE READ GADGET allows you to switch between these two methods. This gadget has two settings: REAL and FAKE. The meaning of each setting is as follows: REAL When the SCAN LINE READ GADGET is set to REAL, A64 will use the Amiga's hardware to get the current scan line. This method is the more compatible of the two and should be used whenever possible. There is one problem with using this method. Because of internal timing in the Amiga some scan lines can not be read. Because of this, if a C64 program is waiting for one of these scan lines it will lock up waiting for something that will never happen (You can either select FAKE, described below, or reset A64 to unlock the program). Because of this problem A64 supports another way of reading the scan line registers, explained below. NOTE: It has been reported that with certain video devices connected to your Amiga, like GenLocks, A64 will fail to run with the SCAN LINE READ gadget set to REAL. Because of this problem the default setting is FAKE, but if you do not have one of these devices connected to your Amiga you should switch this setting to REAL. FAKE When the SCAN LINE READ GADGET is set to FAKE, A64 will simulate the function of the scan line registers. This method will allow some C64 programs to run that wouldn't ordinarily with the above mentioned REAL method. This method will allow all scan lines to be read, but because of the fact that it is a "fake" reading it will not be in sync with the true scan line. This will not cause 3-21 major problems with most C64 programs, but it will throw off the timing of any program that uses the scan line registers for that purpose. ROUND SCAN LNS GADGET The C64 has the ability to change its graphics modes many times during one screen. Because of a minor incompatibility with a small number of C64 programs A64 may not change graphics modes at the exact scan line that the C64 intended causing garbage graphics data to appear in a couple of scan lines on the screen. The ROUND SCAN LNS GADGET will allow you to correct this problem with some programs. This gadget has two settings ON and OFF. When ON is selected A64 will force the changes in the screen to drawn at the nearest 8 scan lines and when OFF is selected this feature will be disabled. It is really difficult to explain the ROUND SCAN LNS GADGET without getting overly technical. Simply, if you are running a C64 program and parts of the screen do not look correct try turning ON the ROUND SCAN LNS setting to try and correct it. The ROUND SCAN LNS GADGET can also cause some program's screens to appear totally wrong. In this case the this option should be turned OFF. OK AND CANCEL GADGETS Selecting OK will preserve all changes to the RASTERS settings and selecting CANCEL will ignore any changes and abort the operation. SPRITES KEY SEQUENCE: None This section describes sprites. Sprites are independent graphic images that are not part of the screen in the normal sense. If you are unfamiliar with sprites we recommend reading one of the many books available on C64 graphics. The C64's sprites and the Amiga's sprites are about as compatible as fire and water. Trying to get Amiga sprites to behave like C64 sprites is not an easy feat. One of the biggest problems that you will notice almost immediately is that the sprites will flicker. Because of size differences between Amiga and C64 sprites there are not enough Amiga sprites to emulate all of the C64's sprites at one time. Because of this Amiga sprites need to be re-used, causing the flicker. The more C64 sprites that are used and if they are expanded horizontally the worse the flickering gets. There are also other problems created because 3-22 of incompatibilities between Amiga sprites and C64 sprites. Sprite collisions and sprite priorities are not 100% compatible. Most of the problems with emulating C64 sprites are caused by restrictions in the Amiga's hardware. It's hard to believe, but there are some things a C64 can do that an Amiga can't. compatibility with C64 sprites has been greatly improved since earlier versions of A64, but there are still problems that are not easily corrected. Many people have suggested using "BOBs" to emulate the C64 sprites, but unfortunately doing this would slow A64 down to a crawl. We will continue to work on sprites, but unfortunately there will always be incompatibilities. The SPRITES menu option allows you to change how A64 handles C64 sprites. When selecting SPRITES you will be prompted with a requester containing several gadgets. The function of each gadget is as follows: MONO SPRITES GADGET The C64 has two types of sprites: multi-colored sprites that use 4 colors and standard sprites that use 2 colors. The emulation of multicolored sprites can decrease the speed in which A64 runs some programs. The MONO SPRITES GADGET allows you to force A64 to use standard sprites in place of multi-colored sprites. This will allow A64 to run some programs faster. This gadget has two settings: ON and OFF. Selecting ON will enable the replacement of multi-colored sprites with standard sprites and selecting OFF will disable this feature. SPRITE COL GADGET The C64 is capable of generating interrupts when two sprites collide with each other. Because of incompatibilities between the Amiga hardware and the C64 hardware these collisions are not emulated 100%. The SPRITE COL GADGET allows you to disable sprite to sprite collisions. This gadget has two settings: ON and OFF. Selecting ON will enable sprite to sprite collisions and selecting OFF will disable them. FRGRD COL GADGET The C64 is capable of generating interrupts when a sprite collides with part of the normal screen. Because of incompatibilities between the Amiga hardware and the C64 hardware these collisions are not emulated 100%. The FRGRD COL GADGET allows you to disable sprite to foreground collisions. This gadget has two settings: ON and OFF. Selecting ON will enable sprite to foreground collisions and selecting OFF will disable them. 3-23 NOTES: Sprite to foreground collisions are more compatible than sprite to background collisions and less problems can be expected with this type of collision. The SPRITE COL GADGET and FRGRD COL GADGET can be used to get endless lives in many C64 games by disabling collisions. PRIORITIES GADGET The C64 is capable of displaying sprites either in front of the rest of the screen or behind it. This capability is called sprite priorities. Because of incompatibilities between the Amiga hardware and the C64 hardware these priorities are not emulated 100%. The PRIORITIES GADGET allows you to select how A64 handles these priorities. This GADGET has three settings: NORM, FRONT and BACK. Selecting NORM will force A64 to do its best to emulate the C64's sprite priorities. Selecting FRONT will force A64 to display all sprites in front of the rest of the screen and selecting BACK will force A64 to display all sprites behind the rest of the screen. DATA RATE GADGET The DATA RATE GADGET allows you to change the rate in which A64 updates the C64 sprite images. This gadget is a string gadget and it allows you to enter a five digit number that corresponds to the rate in which A64 updates the C64 sprite images. This number can range from 1-65535 and the way A64 interprets it is as follows: A64 uses the DATA RATE value as a countdown to update the C64 sprite images. A64 subtracts 1 from this value 60 times per second and when the value counts down to 0 A64 resets the counter and updates the sprite images. For example if you set this setting to 1 then A64 would subtract 1 from it 60 times per second (1-1=0) and would result in A64 updating the sprite images 60 times per second. See: REFRESH RATE TABLE in the GRAFIX section. HARDWARE RATE GADGET The HARDWARE RATE GADGET allows you to change the rate in which A64 updates the Amiga sprite hardware used to emulate the C64 sprites. This includes such things as sprite colors, sprite positions and sprite re-use (what causes the flickering of sprites). This gadget is a string gadget and it allows you to enter a five digit number that corresponds to the rate in which A64 updates the Amiga sprite hardware. This number can range 3-24 from 1-65535 and the way A64 interprets it is as follows: A64 uses the HARDWARE RATE value as a countdown to update the Amiga sprite hardware. A64 subtracts 1 from this value 60 times per second and when the value counts down to 0 A64 resets the counter and updates the Amiga sprite hardware. For example if you set this setting to 1 then A64 would subtract 1 from it 60 times per second (1-1=0) and would result in A64 updating the Amiga sprite hardware 60 times per second. See: REFRESH RATE TABLE in the GRAFIX section. OK AND CANCEL GADGETS Selecting OK will preserve all changes to the SPRITES settings and selecting CANCEL will ignore any changes and abort the operation. NOTE: All the SPRITES settings can have dramatic effects on C64 programs utilizing sprites. By changing these settings you can dramatically change the speed, appearance and useability of many C64 programs, especially games. When you bring up A64 Prefs you may notice some images disappear from the C64 screen, this is normal. These images are C64 sprites. A64 Prefs does not support C64 sprites so they will disappear from the screen when it is entered. ALL GFX KEY SEQUENCE: None The most time consuming part of A64 is the emulation of C64 graphics. The ALL GFX menu option allows you to turn off all of A64's graphics allowing A64 to run at much greater speeds. This option can be useful to temporarily disable all graphics allowing a C64 program to perform some operation much faster than it normally would. For example if the program you're running does extensive calculations or if you want to listen to a program's sound at the fastest possible speed. The ALL GFX menu option has two settings: ON and OFF. You can select one or the other of these settings and selecting one automatically unselects the other. The current selected setting is shown by displaying a checkmark next to it. Selecting ON will enable all of A64's graphics. 3-25 Selecting OFF will stop A64 from updating any C64 graphics. NOTES: If you turn off all of A64's graphics don't forget that you did or it will appear that A64 has locked up because the screen will not change, even when you reset A64. This option is not saved as a configuration setting. REFRESH RATE TABLE Listed below is a table of refresh values and their corresponding rates that can be used to set the SCREEN REFRESH RATE, SPRITE DATA RATE and SPRITE HARDWARE RATE settings. Your are not limited to the values in this table, but they can be used for reference. REFRESH RATE VALUE REFRESH RATE ------------------ ---------------- 1 60 x per second 2 30 x per second 3 20 x per second 4 15 x per second 5 12 x per second 6 10 x per second 10 6 x per second 15 4 x per second 30 2 x per second 60 1 x per second 120 1 x per 2 seconds 600 1 x per 10 seconds 6000 1 x per 100 seconds (1.66 minutes) 65535 1 x per 1092.25 seconds (18.20 minutes) See: SCREEN REFRESH RATE GADGET, DATA RATE GADGET and HARDWARE RATE GADGET in the GRAFIX section. 3-26