CPCEC Amstrad CPC emulator
and its ZX Spectrum sibling ZXSEC
20194 hits

Foreword

CPCEC is an emulator of the family of home microcomputers Amstrad CPC (models 464, 664, 6128 and Plus) whose goal is to be loyal to the original hardware and efficient in standard modern systems. Thus it brings a faithful emulation of the Z80 microprocessor and it replicates the behavior of the CRTC 6845 and Gate Array video chips, the PSG AY-3-8912 sound chip, the remaining circuits found in the original hardware, and the tape deck and floppy disc drive that made possible loading and running software.

ZXSEC is an emulator of the Sinclair Spectrum family (48k, 128k, +2/Plus2 and +3/Plus3) based on the components it shared with the Amstrad CPC family: the Z80 microprocessor, the PSG AY-3-8192 sound chip, the tape system and the NEC765 disc drive controller.

The default build of CPCEC requires a Microsoft Windows 2000 operating system or later, while the SDL2 build requires any operating system supported by the SDL2 library. The minimal hardware requirements are those fitting the operating system, and it's advised that the main microprocessor runs at 400 MHz at least. Screen resolution in pixels must be 800x600 at least. A sound card is optional. Using a joystick is optional, too.

The source code of CPCEC and its binaries follow the GNU General Public License v3, described in the file GPL.TXT within the package.

Gallery

Arkanoid 2 (1988 Imagine) CPC 464 Skweek (1989 Loriciels) CPC 6128 Cobra (1986 Ocean) Spectrum 48k Zub (1987 Mastertronic) Spectrum 128k

Mega Phoenix (1991 Dinamic) CPC 464 Beast Preview (1992 Overflow) CPC 6128 Dark Star (1984 Design Design) Spectrum 48k Deliverance (1990 Hewson) Spectrum 128k

Mission Genocide (1987 Firebird) CPC 464 Logon's Run (2017 Logon System) CPC 6128 Starion (1985 Melbourne House) Spectrum 48k Mot (1989 Opera Soft) Spectrum Plus3

Samurai Trilogy (1987 Gremlin) CPC 464 PhX (2018 Condense) CPC 6128 Vectron (1988 Firebird) Spectrum 48k Cray 5 (2011 Retroworks) Spectrum Plus3

Acknowledgements

This emulator owes its existence to a series of people and societies that are listed as follows:

• The firmware files included in the package are Amstrad's properties, who allows the emulation of their old computer systems and supports the distribution of their firmwares as long as their authorship and contents are respected, and whom I wholeheartedly thank the creation of those magnificent computers and the good will towards their emulation.
• This emulator was my final project for the Computer Engineering postdegree at the Distance-Learning National University (Universidad Nacional de Enseñanza a Distancia, UNED), a project directed by professor José Manuel Díaz Martínez and ultimately awarded a 100% and the right to a honorable mention.
• The documentation about the system comes from cpcwiki.eu, cpc-power.com, cpcrulez.fr and quasar.cpcscene.net.
• The alpha tests were handled by Denis Lechevalier.

Version log

• 20190314 -- first public release.
• 20190317 -- second public release. Fixed Win32 joystick bugs: JoyGetPos returns ZERO on OK, not on ERROR.
• 20190318 -- third public release. By default the window shows a menu; new option -+ hides it.
• 20190325 -- fourth public release. Onscreen indicators (hide them with -O); fixed bugs in ZXSEC that slowed emulation down when the frameskip wasn't zero, and another bug in audio recording on WAV files.
• 20190331 -- fifth public release. Tapes can be browsed, either by file position (WAV and CSW) or by block (CDT, TZX and TAP).
• 20190404 -- sixth public release. Fixed a Z80 emulation bug in IRQ logic. Configuration (computer model and file paths) is kept across sessions in a INI file.
• 20190408 -- seventh public release. Fixed a bug in the YM3 file recording, another one in the ZXSEC internal timings, and one more in the debugger commands with optional parameters.
• 20190419 -- eighth public release. Added options for image and sound interpolation; tape automatically rewinds itself when it reaches the end (à la FUSE); fixed a bug in TZX files that store 0 instead of 8 in the "used bits" field, another bug in CUSTOM INFO blocks in TZX files, and another one when ZXSEC loads a 48K SNA file in Plus3 mode (users should manually switch to a safe model beforehand anyway). INI files now remember the names of the last used files.
• 20190430 -- ninth public release. Softer B/W Spectrum palette; fixed bug in FDC sector size calculation if GAP datas are stored (Loriciels' discs); added simple memory contention to ZXSEC ("Amaurote", "Black Lamp", "Puzznic", "Sly Spy", "Zub"...).
• 20190524 -- tenth public release. Added support for CDT/TZX file blocks 0x24 and 0x25 (loop start and ending) (cfr. BATMAN.TZX), fixed bugs in the handling of weak sectors in DSK files (cfr. "Titus Classiques"), YM file recording is reentrant, fixed a bug in INI files with empty fields and added the option `autorewind <0|1>` to rewind (or remove) a tape when playback reaches the end.
• 20190526 -- minor patch fixing a bug in autorun mode: opening menus and switching windows cancelled the automatic keyboard.
• 20190731 -- eleventh public release. Added a new UI-based debugger (typing commands is no longer needed) and support for ZIP archive reading based on PUFF.C from the ZLIB project, upgraded GCC to 5.1.0 and removed all `inline` tags (they did more harm than good), and generally reworked all internals to make them OS-independent. Several details improved as well: the file selector fixes a bug in Win10 (and in some cases in Win7), "browse tape" dialog shows the file name, Spectrum Plus3 automatically becomes Plus2A to load tapes, `auto rewind` shows up in Edit menu and fixes bugs in CSW files, and sound emulation has improved, for example "Terminus" on CPC plays sound and "Agent X II" on Spectrum is no longer noisy.
• 20190809 -- minor patch restoring the "silent" discarding (i.e. without error codes) of write operations in read-only discs and allowing the automatic booting of IBM-formatted discs.
• 20190817 -- minor patch fixing a crash when booting tapes right when the automatic frameskip kicks in.
• 20190831 -- minor patch fixing several bugs (booting two-sided discs with FLIP SIDE option on, recording snapshots or tapes after loading a snapshot or tape from a ZIP archive), improving several details (loading snapshots with memory compression, emulating up to 576 kB RAM) and redefining the menus (Edit is divided into Edit and Settings, Image and Sound become Video and Audio, new video filter functions...) and the command line: "-+" now limits the zoom to integer values; "-!" inherits the option of hiding the menu.
• 20191003 -- twelfth public release. Precise (albeit not perfect yet) memory contention and ULA noise ("snow") on Spectrum: "48K Timing Tests" passes all tests but 36 and 37, and "128K Timing Tests" fails on just six tests. "Mask 3: Venom Strikes Back" draws the attribute and border effects on their precise locations on all platforms (48K, 128K/Plus2, Plus3) and Software Creations' "Black Lamp", "LED Storm" and "Sly Spy" behave well on 128K machines. Improvements in the debugger: fixed disassembly panel invalid cursor locations, added optional tall characters, avoided debug+pause clashing, new key M toggles memory dump ROM+RAM and RAM-only modes. Improved ZIP handling (ZIP archives are no longer locked, files within archives are filtered by extension), user interface fixes.
• 20191004 -- minor patch making the debugger options set with V and M stick between sessions.
• 20191117 -- thirteenth public release. More precise emulation of type 1 CRTC (by default instead of 0) in CPCEC ("From Scratch", "Pinball Dreams"...) and 48K memory contention in ZXSEC ("Starion", "Black Lamp"...). CPCEC also allows choosing the length of the V-hold signal (for example "Thunder Blade" needs a short signal) and whether horizontal sync must be flexible ("Batman Returns", "Pinball Dreams"...) or not ("CPC 30th Anniversary Megademo", "PhX"). Unfortunately, some demos that worked well in past versions now suffer problems that cannot be solved by selecting another CRTC. Removed third joystick button in CPCEC, no real joystick ever included it. The ZXSEC joystick is Sinclair 2 by default.
• 20191130 -- minor patch fixing a bug when running CPCEC and ZXSEC on a screen shorter than 600 px, another one when recording a WAV file, and another one in the port logic of CPCEC ("Knight Rider", OUT &0088,&88 must not reach the Gate Array, but "Hero Quest", OUT &00C0,&C0 must reach it). The CRTC types 0 and 2 have improved ("Face Hugger Ultimate Megademo: Tantrum", "5KB Megademo 3", "Power System Megademo: Glooms"...) but cannot handle "Pinball Dreams" yet, unlike CRTC types 3 and 4, that together with CRTC1 support this game now.
• 20191227 -- fourteenth public release. Visual improvements: the green screen palette is closer to the original, the vertical filters ("Y-Masking") are compatible with the interlaced modes, mixing X-Masking and Y-Masking together shows a checkered pattern. Internal improvements: the new traits of the CRTC registers 3 and 9 and the delays between the Gate Array, the Z80 and the CRTC finally can emulate "Pinball Dreams" as a whole for all the CRTC types and solve the problems in several demos ("Scroll Factory", "Still Rising", parts of "The Demo"...) and games ("Action Fighter", "Storm Warrior", "Usagi Yojimbo"), although some titles still need particular CRTCs ("PhX" CRTC0, "Onescreen Colonies" CRTC1, etc.) to work correctly.
• 20191231 -- minor patch fixing a bug in the FDC (bit 6 of SENSE DRIVE STATUS must react when the user changes discs: "Fugitif") and a regression in CRTC0 (detect REG6<REG4 rather than REG6<=REG4: "5KB Megademo 3: Nayad"). Happy new year 2020!
• 20200101 -- minor patch fixing a regression in CRTC0 caused by the previous patch ("Scroll Factory", intro of "Pinball Dreams", "Overflow Preview: Part 1") and improving its heuristics ("Overflow Preview: Part 3").
• 20200229 -- fifteenth public release. Added support for Amstrad Plus hardware: extended colours, soft scrolling, hardware sprites, programmable raster interruptions, DMA channels, ROM cartridges, etc. Added fifty more tape schemes to speed up the reading of bytes and even whole blocks. Improvements in the disc drive emulation: new discs (by default the DATA format shared by CPC and Spectrum Plus3) can be created on the fly, emulation of protected games from Design Design ("2112 AD"), The Edge ("Palitron"), Titus ("Prehistorik" and "Moktar/Titus the Fox"), bugfixes (READ ID: "5KB Demo 3", "Daley Thompson's Olympic Challenge" and "Turbo Copy III"; FORMAT TRACK converts old-style MV - CPC discs into new-style EXTENDED ones, and cleans up useless data at the end of the disc). CPCEC honours the RAM size (up to 576k) and CRTC type stated by a snapshot ("Postscript" demo) and so does ZXSEC, that can read Z80 snapshots now and allows 48K SNA files to be either strict (the original format) or relaxed: 128K headers on 48K data. Control-F2 avoids accidental recording of snapshots after a reset. Fixed a bug that happened when combining Y-Masking and Half Scanlines. Extended ZIP archive support to handle pipeline-generated (i.e. the final headers are the right ones) archives. Sources are distributed together with the binaries instead of being delivered upon demand.
• 20200307 -- minor patch avoiding a hang in globbing(), improving snapshot compatibility (WinAPE and ACE employ slightly different CPC+ blocks) and removing several useless details. The optional firmware packages now include the corresponding cartridges.
• 20200314 -- first anniversary! minor patch fixing issues in the Plus demos "CRTC3" and "Eerie Forest" for Amstrad Plus.
• 20200331 -- minor patch providing further fixes for Plus demos "CRTC3" and "Synergy 4" (top left sprites disappear after few seconds, though) and adding the command Shift+Space (skip scanline) to the debugger.
• 20200404 -- minor patch fixing the DMA handler (all commands but LOAD can be combined together) and removing several "kludges" for Plus but the one for "Black Sabbath": thanks to Norecess464 for locating the bug. Also, -C now becomes -C0..4.
• 20200406 -- minor patch adding partially multiplexed Plus sprite rendering: "Synergy 4" recovers its top left sprites.
• 20200418 -- minor patch with improvements in the interrupt counter (it starts with the first HSYNC fall after the VSYNC rise -"Onescreen Colonies"- unless on Plus where it can start when the VSYNC rise happens together with the HSYNC fall: "Black Sabbath"), the hardware ports (PIO port A returns zero when reading it in write mode unless on Plus where it returns 255 -"Tire au Flan"-, PIO port B must set VSYNC in the middle of the screen when the CRTC requests it -"Chany Dream End Megademo"- and the Gate Array's 0-191 byte range requires a more rigid port logic -"Overflow Preview 3"-) and the debugger: disassembly parameters are vertically aligned and the hardware information panel is aligned to the ASCII memory dump. Fixed a bug in the ZIP archive header seeker, too.
• 20200420 -- minor patch fixing the HSYNC signals' black stripes from "Chany Dream End Megademo" on CRTC1, "Onescreen Colonies" on CRTC0, etc., as well as the value of MEMPTR in JR cc,$RR and DJNZ $RR and the logic of BIT n,r,(IX+$XX): the error rates of ZXSEC in the 2012 RAXOFT tests are Z80FULL 10/152, Z80CCF 70/152 and Z80MEMPTR 4/152.
• 20200430 -- sixteenth public release. Now you can compile CPCEC and ZXSEC with SDL2 (featuring its own graphical user interface) for multiple operating systems thru the option -DSDL_MAIN_HANDLED; the precompiled files CPCEC.ELF and ZXSEC.ELF for 32bit GNU/Linux are included, too. New support for extended ROM profiles through INI files enumerating up to 257 16K ROM blocks. Further Z80 tweaks: the new error rates of ZXSEC in the 2012 RAXOFT tests are 8/152 Z80FULL, 5/152 Z80CCF and 0/152 Z80MEMPTR.
• 20200503 -- minor patch improving the behavior of the Z80 operations INI, IND, INIR, INDR, OUTI, OUTD, OTIR and OTIR: the 2012 RAXOFT tests (Z80CCF, Z80FULL and Z80MEMPTR) score zero errors. Slightly more precise automatic frameskip.
• 20200505 -- minor patch focused on the SDL2 toolkit: fixed a bug when confirming overwriting files, and improved file browsing across directories by pointing by default to the previous directory.
• 20200509 -- minor patch improving the synchronisation between Z80 and video on ZXSEC: the ULA48 test already worked before, but ULA128 had problems; now both work well. Added the option -W (use the full screen rather than a window) and improved the SDL2 handling of bigger windows.
• 20200603 -- seventeenth public release. Added stereo sound. Fixed a bug in the CPC PIO (the read-only mode of port A allowed writing), another bug in the tape analysis (CPCEC: the algorithm for TITUS caused trouble in "The Blues Brothers"; ZXSEC: Speedlock5 didn't recognize the heading noise; both systems add patches to shorten the initial delays), another one in the loading of CPC snapshots (a snapshot saved on Plus hardware without the "CPC+" block showed a completely black palette), another one in the Z80 debugger (the command 'P0 could generate an infinite disassembly), another one on tape handling (reading a WAV file must use >128 as reference instead of >=128) and some problems in Win32 (the screen stopped updating after pausing, switching windows in and out) and SDL2 (boot message errors weren't shown; the filename sorting algorithm was slow).
• 20200606 -- minor patch with surround sound: the user can set the channel separation to 0% (mono), 50% (surround) or 100% (stereo).
• 20200616 -- minor patch adding several tape analyses and removing the patch that shortened the initial delays (it caused problems). Several changes in SDL2 (fewer warnings, disc drive cache in Win32) and in the Z80 debugger (more content: 256 bytes of memory dump and 32 bytes of stack).
• 20200622 -- minor patch reducing memory footprint (extra ROM memory is only allocated if the user loads a "profile"), rendering SYNC signals as black rather than as the current border, and fixing the 3D cylinders part of "PhX" on CRTC1; the "ball worms" and the final scroller stay bad on CRTC3 and CRTC4, though.
• 20201010 -- eighteenth public release. Fully rewritten CRTC logic, with an internal event system that extends demo compatibility (for example "Chapelle Sixteen", "Madness Demo" and "S&KOH" for CRTC1) and a fully multiplexed Plus sprite renderer. More disc protections (ERE, UBI) are supported, WRITE DELETED DATA updates the corresponding flag in the sector table. New Dandanator support, read-only ("Sword of Ianna"). Preliminary Playcity support, limited to the two extra PSG and the NMI trigger. New video recording based on an intermediary format XRF, and including a tool allowing to convert it into AVI files. Improvements in the SDL2 interface, with a bigger font (12px rather than 8px) and vertical alignment in menu keyboard shortcuts. Added new debugging functions (looking at graphics in memory with key "W", trapping the opcode $EDFF as a breakpoint, etc.) and moved breakpoints from "T" to "." . Removed CPCEC.ELF and ZXSEC.ELF as they're bound to a single OS (Linux Mint 18 32bit) and the user must compile the binaries anyway. Moved the configuration files in non-Windows systems from CPCEC.INI and ZXSEC.INI to .cpcecrc and .zxsecrc as customary on Unix. Tweaks for CLANG compatibility.
• 20201012 -- minor patch adding mouse support to the user interface for SDL2.
• 20201020 -- minor patch fixing a bug in the Dandanator support (the "LD (IY+n),A/B/C" operations must work with any "n" value, instead of just 0: thanks to Spirax for the report) and another one in the CRTC (counter HCC is 8 bits long: "Camembert Meeting 4 Demo" stops showing a line of garbage between the top and the middle panels), adding SDL2_DOUBLE_QUEUE as an optional SDL2 compilation flag (some systems need an audio buffer longer than the default 8 frames) and using a different pixel pattern when both X-Masking and Y-Masking are enabled.
• 20201022 -- minor patch adding mouse wheel support to the SDL2 user interface and an option to set whether disc write conflicts in CPCEC and ZXSEC are strict (they raise errors) or relaxed (they do nothing).
• 20201024 -- minor patch solving a problem in the SDL_WINDOWEVENT_EXPOSED event, inverting the black/white bits in ZXSEC's graphics viewer and pointing CPCEC's viewer at RAM rather than ROM.
• 20201028 -- minor patch improving Issue-2 emulation on Spectrum 48K: "Abu Simbel Profanation" and "Rasputin 48K" work on 48K Issue 2 and fail on the other models, as expected.
• 20201111 -- minor patch adding mouse tracking to the SDL2 interface and making XRF file recording less memory-consuming.
• 20201122 -- minor patch fixing a crash when using the SDL2 interface to save a file in the root path, and enabling automatic SDL2 detection on compile time.
• 20201124 -- minor patch adding AMSDOS header detection to ROM profile loading, following an idea from Sid.
• 20201130 -- minor patch further extending ROM profile loading with four new fields: "type", "bank", "crtc" and "fddc".
• 20201212 -- nineteenth public release. The Windows version can use DirectDraw instead of GDI, and the SDL2 version uses Textures instead of Surfaces: performance rises when hardware acceleration is available. Just in case, however, command line parameter `-!` and the menu option "Video: Software render" can be used to disable the hardware acceleration in systems where it's missing or performs worse than pure software. CPC bugfix: PSG handles register 14 separately, as expected by "Gremlins (v1)". Spectrum bugfix: 128K ghost ports are properly emulated, the demo "Tiratok" plays music at last. New debug command "Y": fill memory with byte. XRF lists the available codecs on Windows when launched without parameters.
• 20201215 -- minor patch fixing snapshot loading on Spectrum Plus3 and extending the ULA's "snow" behavior ("Vectron") and scope ("Narco Police", "Robocop 3"). The SDL2 UI appends an ellipsis to filenames that are too long to fit within the dialogs.
• 20201220 -- minor patch removing the obsolete console-based debugger from the sources and making the Playcity option stick between sessions. "Software render" is now "Acceleration", as the former was counterintuitive.
• 20210105 -- minor patch fixing a bug in video recording (it turned 44KHz stereo into 88KHz mono) and tape playback (16 and 24 bit WAVE files were improperly supported), extending the joystick support to handle directional controls (thanks to Pelrun for the Win32 and SDL2 code) and letting the Dandanator emulation modify the cartridge (configuration, savestates...) if the user allows it.
• 20210107 -- minor patch fixing a bug in the ASIC's screen split trigger (SSSL must be checked when HSYNC rises, rather than when HDISP rises) and a glitch in the Win32 joystick support, and making the Playcity CTC more responsive.
• 20210114 -- minor patch improving Playcity stereo autodetection ("Alcon 2020" uses the left chip only), adding ROM simulation to Dandanator cartridges ("CPC Soccer") and fixing a bug in Z80 instruction CPI introduced in version 20210105 (RAXOFT tests) and another one in the CRTC1 VSYNC length ("Pheelone").
• 20210115 -- minor patch fixing a bug in the CPC PIO: "Inertie" sends a value to port A, then reads the same value back instead of receiving a PSG register or keyboard bits.
• 20210127 -- minor patch fixing bugs in the Spectrum timing ("LD (IX+n1),n2" and Z80_PRAE_SEND: thanks to Azesmbog for the FPGA test report) and the CPC tape analysis (conflict between Mikrogen and Hi-Tec).
• 20210129 -- minor patch fixing a bug in the CPC PIO ("Super Cars" had stopped working in version 20210115) and improving CRTC1 compatibility (first part of "Ecstasy Demo").
• 20210219 -- minor patch adding a new option, "Video: Blend scanlines" that handles Gigascreen effects (Spectrum demos "Mescaline Synesthesia" and "Tiratok", CPC demos "Batman Forever" and "Mad Leprechaun") and changing the sound synchronisation in SDL2. The AY chip noise generator is now a LFSR. SNA files saved from Spectrum Plus3 set bit 4 of byte 0x0C01E to state that the snapshot requires a Plus3 (Easter egg "Hello There I'm a +3"). The CPC debugger adds an information panel (key 'X') for Dandanator status, and its graphics viewer can show MODE 2 images.
• 20210418 -- twentieth public release. Pixel and scanline filters are now saturation-based (colour aberration, desaturation) rather than luminosity-based (horizontal blur, shading). Fixed bug in XRF-to-AVI recording: VFW32 operations always assumed 16-bit stereo. The film recording options "High resolution" and "High framerate" now stick between sessions, and the first one also applies to BMP screenshots. Added support for block types 0x19 and 0x4B in CDT/TZX tape files, as well as the new disc option "Read-only as default" so the user can choose whether discs are by default read-only or read-write, and this option stacks together with the already extant "Strict disc writes". Added new option "Flip joystick buttons" to CPCEC so users can swap the value of the two CPC joystick buttons, as suggested by SB1903. PSG emulation now catches overflows, regardless of whether they're programming errors (music distortion in "Thing on a Spring") or done on purpose (pipe sound effect in "Thing Bounces Back"). Fixed bug in ZXSEC's Plus3 memory contention ("Firefly" disc release) and improved the beeper (oversampling: Utz's "Quattropic"). ZXSEC snapshot handling is now more strict or flexible (changing models as often or as seldom as possible) depending on the option "Strict SNA files".
• 20210428 -- minor patch fixing bugs in several tape fastloaders and in the firmware INI handler (spaces must be trimmed on both sides of each string), and adding inverse video 8-bit characters to the debugger's memory dump.
• 20210522 -- minor patch fixing bugs in the ASIC (modifying the SSCR has an immediate impact; SSSL is checked when HCC==R1 rather than when HCC==R0; reported by NoRecess), the PSG (register 15 is valid, even if the hardware doesn't use it: the Plus demo "Phat" plays its music properly now), the Z80 (EI always delays the next IRQ, no matter the previous state of the interrupt enable flag, and OUTI sends the OUT signal during its last microsecond rather than during the second-to-last; "KKB First" demo needed both fixes to run correctly; reported by Hicks) and the FDC (errors imply delays that must be emulated: the original protected disc of "Bad Cat" accidentally relies on this; reported by Dlfrsilver). The debugger accepts very simple expressions (additions and substractions) when entering 16-bit values (address of "Go To", length of "Output"...) and the integer zoom allows 50% steps rather than 100% because the default size is technically 200% rather than 100%.
• 20210524 -- minor patch fixing bugs in film recording: field size errors on 64-bit machines, improper AVI header sound sample size on 8-bit output (both reported by Cpcitor), and accumulated dirt between multiple recordings within the same session. XRF also shows the length of the output file.
• 20210526 -- minor patch aligning the X-Masking video effect to the right instead of the left. The debugger expressions accept three new operators: & (AND), | (OR) and ^ (XOR). XRF shows the output file's accurate byte length rather than just the megabytes, and running it without a target parameter prints the source video parameters and the expected size.
• 20210609 -- minor patch adding lightgun emulation for CPC (Trojan, Gunstick and Westphaser on joystick port) and Spectrum (Gunstick on Sinclair 1 and Kempston ports), recreating a CRTC0 quirk (when R6==0 a single scanline is shown, rather than none as in other CRTC types) and improving the choice of the filler colour when half scanlines are on. The SDL2 version now handles mouse clicks when the button is up to improve consistency with other user interfaces. Tape acceleration options stick between sessions.