History of ep128emu releases

Changes in version 1.6.1

ep128emu home page has been moved to http://sourceforge.net/projects/ep128emu/.
Video and sound driver can be selected with the 'video_driver' and 'sound_driver' configuration options. The available video drivers are 'null' (no video and keyboard - not very useful), 'sdl', and 'opengl'. Sound drivers are 'null' (disable sound), 'sdl', 'alsa' (Linux only), and 'winmm' (Win32 only, does not work very well yet).
New, OpenGL based video driver that can be enabled with the 'video_driver=opengl' option. Allows scaling the emulator window by any ratio (e.g. from 720x540 to 1024x768), optionally with linear filtering, and is faster than the old SDL driver if a high resolution is used. Double buffering and 'blit_on_change_only' are supported, however, there is no implementation for interlaced display and half refresh rate. 'video_hw' is ignored in GL mode, as it always uses hardware acceleration. See the file '.ep128rc.gl' for more details.
If the OpenGL video module is used, a transparent console overlay may be enabled (with the 'gl_console=1' option). This is most useful in fullscreen mode where the console messages could not be seen otherwise. Messages are shown when the keyboard is in program control mode (F12), and are hidden in normal emulation mode.
The disadvantage of enabling the console is increased CPU usage, and it also automatically turns on double buffering and disables 'blit_on_change_only'. So, the GL console is best used on fast computers.
Improved color correction: gamma, contrast, and brightness can be specified for each color channel (R, G, B), in addition to the overall values that affect all channels. For example, the 'gamma_b' option sets the gamma correction for the blue channel, 'min_intensity_g' controls the minimum intensity (brightness) of the green channel etc.
Emulator messages can be logged to a file with the 'logfile=filename' option, and it is possible to disable printing to stderr with 'msg_stderr=0'.
Direct floppy access under Windows 2000/XP; set the image name to '\\.\A:@80,2,9' or '\\.\B:@80,2,9' for a 3.5" 720k disk (note: the disk geometry must be specified, as the emulator cannot detect it). 5.25" disks were not tested.
Bug in disk emulation after snapshot loading may be fixed now.

Some functions of the emulator can be accessed with multiple keys, for improved compatibility with systems where the original keys could not be used for some reason.
The new keys are:

Reset CPU frequency to 4 MHz	Keypad Enter, Keypad *
HOLD / Quit emulator	Pause, PageUp
STOP	Print Screen, End

New sound driver for Win32 that uses the waveOut interface, and is enabled with 'sound_driver=winmm'. This is experimental, and currently not really usable.
Added more example configuration files.

Changes in version 1.6.0

Implemented floppy emulation, based on code from 'ep32' emulator (copyright by Kevin Thacker and Vincze Bela Gyorgy, under the GNU General Public License). Up to 4 drives can be emulated, floppy images with 40 to about 224 tracks, 2 sides, and 9 sectors per track are supported (this means a capacity range of 360K to 2016K).
Under Linux it may be possible to use the floppy device (/dev/fd0*) directly, although was not tested extensively (note: 1.44 MB PC floppies with 80 cylinders/2 heads/18 sectors are not supported, however, by copying images/disk1440 to an empty 1.44 MB disk (e.g. dd if=images/disk1440 of=/dev/fd0u1440) it is possible to create a floppy that can be read both by EXDOS and the Linux kernel).
Disk images used by the emulator can also be mounted as loopback devices (only do this when ep128emu is not running).
It is also possible to make the emulated floppies 'write-protected', with the 'chmod' command under Unix-like systems or 'attrib' under Win32.
Currently, there are some limitations: single sided disks are not supported (this means 180K disks cannot be used), the number of sectors per track must be 9 (although it is not sure if EXDOS 1.3 can read disks in other formats), and reading/writing whole tracks is not possible. As a result of the latter limitation, floppies cannot be formatted from the emulated system, you should use images copied from existing disks, or the empty pre-formatted disk images included with the emulator.
For more details about floppy emulation, see .ep128rc.
Significantly improved the buffering algorithm of the SDL sound driver, to allow smooth display update even with large 'sndbuf_hw' settings that are needed on Win32 systems, as long as 'sndbuf_sw' is sufficiently low. Experiment with these options for best performance.
The 'Keypad Del' key can be used to set an alternate Z80 clock frequency that is specified with the 'cpu_altfrq' option.
This is useful to temporarily switch to a high frequency (e.g. 25 MHz, or even 100 MHz on sufficiently fast systems) to speed up some operations e.g. copying large files between disks, and then revert to the standard 4 MHz (using 'Keypad Enter') once the high speed is no longer needed.
Note that tape transfers will become slower with a faster Z80 setting, so it is not recommended to use this while copying files from/to tapes.
Removed 'VRAM_TIMING' Makefile option, as the more advanced video memory timing algorithm is always used now; it has been optimized though, so is not as slow as in the previous version.
Added 'vram_latency' configuration option, in addition to the existing 'vram_clock', for better control of video memory timing.
The 'nowait_freq' option can be used to set a Z80 clock frequency above which all memory timing emulation is disabled (if the CPU is running at a very high frequency, the speed of the emulated system differs from the original machine anyway, with or without memory wait states, so having them would only slow down the emulator).
Automatic switching of half refresh rate is now disabled when double buffered video is in use, as it caused display problems.
Pre-formatted disk images, and empty tapes of various sizes are included with the emulator (360/720/1440/2016K disks, and 5/10/30/60 min. tapes), for use on systems (e.g. Win32) where utilities to create them (dd, mformat etc.) are not available.
Minor coding improvements.

Changes in version 1.5.2

Significantly improved CPU timing (most - though still not all - opcodes now take the correct amount of cycles to execute).
Improved the emulation of memory wait states, now all the three modes (no wait, wait on reading first byte of an opcode, wait on all access) are supported. Unfortunately this makes the CPU emulation slower.
Experimental video memory timing; one of two possible implementations can be selected at compile time (see Makefile): the simple version waits two CPU cycles on any video memory access (this is the default), and the more advanced code synchronizes to a clock frequency that can be adjusted with the 'vram_clock' option (enabling this one results in a major slowdown of CPU emulation). The 0xBF I/O port has no effect on video memory timing (this is the correct behavior, according to documentation), unlike in previous versions of the emulator.
Optimizations in NICK emulation for improved performance.
Changes to buffering in SDL sound driver; latency is now slightly worse, but the risk of getting buffer underruns is reduced, even with smaller buffer sizes.
It is now possible to update the display at 25 Hz instead of 50 Hz (this only affects copying to the screen, the NICK emulation always runs at 50 frames per second), for improved performance with slow video drivers. Enabled by 'half_refresh' option.
SDL sound driver can automatically switch between half and full refresh rate depending on current state of the sound buffer. More details about this can be found in .ep128rc.
INT1 and INT2 states had inverted polarity in previous versions, due to incorrect documentation; this is now fixed (several programs run better).
Fixed bug that caused a crash with certain LPT margin settings (this often occured after reset).
Lower byte of interrupt vector used in interrupt mode 2 is now assumed to be 0xFF, allowing some games using this mode to run.
Fixes to Z80 overflow and half-carry flags in some arithmetic operations.
Reset now only turns off the tape motor, and does not behave as if F10 has been pressed.

Changes in version 1.5.1

The emulator is now released under the terms of the GNU General Public License.
Further improved DAVE emulation, now all the polynomial counters generate the same bit sequence as a real DAVE chip. Also fixed the polarity and levels of the sound generators and DAC output, and the emulator now generates unipolar signals like the original machine (this fixes some demos where sound was almost inaudible). The new sound code is slightly slower, though.
Highpass filters with controllable frequency (0 to 100 Hz) can be applied to the sound output, to remove DC offset (configuration options 'dcblock_1' and 'dcblock_2').
Sound volume can be controlled with the 'volume' option (also allows inverting the output signal).
Writing to tape at 2400 bits/second may work now.
Fixed bug in ALSA code that sometimes failed the initialization.
Minor code changes in some source files.

Changes in version 1.5.0

Major improvements to DAVE emulation, most of the sound code has been rewritten. The new implementation is based on extensive testing of a real Enterprise 128 with various DAVE register settings, and analysis of recorded sound output.
Highpass and lowpass filters, ring modulation, and distortion using polynomial counters are now emulated accurately, and reproduce the sound output of the original machine fairly well, even in cases when multiple effects (e.g. polynomial counter distortion + highpass + ring modulation) are applied to the same channel.
The 4, 5, 7, 9, and 11 bit polynomial counters now reproduce the pseudo-random bit sequences of a real DAVE chip exactly, with identical output. The 15 and 17 bit counters do not generate the same bit sequence as the original machine (the length is correct, however), although the difference between long pseudo-random sequences is difficult to hear.
Sound oversample can be now up to 16 (previously it was limited to 8).
The 'enable_bf_bit_1' option has been removed, because this bit is now emulated correctly.
Bug in NICK emulation that caused flickering display with LPTs that have more than the standard 312 lines has been fixed (still need to correctly implement interlaced display and other unusual video settings).
Some configuration options are now checked, and if an invalid setting is found, it is limited to the valid range and a warning is printed.
An unsuccesful initialization of the sound card is now an error instead of a warning.
The snapshot file format has been changed because of the new DAVE emulation code. Snapshots of old versions are still supported, however, older releases (1.4.1 and before) of the emulator cannot read the new snapshot files.
Various (mostly minor) code changes in some source files.

Changes in version 1.4.1

New configuration option: 'blit_on_change_only'. If enabled, only those areas of the display are updated that have been changed since the last frame. Improves performance if the video driver is slow.
Faster tape loading and saving, enabled by setting 'fast_tape_mode' to a non-zero value. The emulator can switch to full speed during tape access (sound is turned off), and then return to the normal speed when the load/save is complete.
New keys for controlling the frequency of the emulated CPU: keypad - decreases CPU speed by 5 percent, keypad + increases by 5 percent, and keypad enter resets the frequency to 4 MHz.
Keyboard usage can be printed with keypad ins.
NICK registers now also appear at ports 84-87, 88-8B, and 8C-8F, in addition to the standard 80-83 range.
Reading from ports 10-1F now returns zero, so EXDOS does not hang at start-up. Emulation of the disk controller is not done yet, but it is possible to use a ram disk.
Tape motor is no longer turned off when switching tape files (play/record is still stopped, though), making it possible to select tapes while the emulated system is searching for a file.
Improved tape utilities: tape_enc can encode multiple files, and there is a new utility (decode1) that can extract data from the 1-bit 24 kHz tape images. decode2 has been renamed to decode8.

Changes in version 1.4

New sound drivers (snd_sdl.c and snd_null.c) have been added, and can be selected at compile time by uncommenting the appropriate lines in Makefile. ALSA is still supported, as it has better performance. With the SDL sound output, it may be possible to compile and run the emulator on systems other than Linux (not tested yet), although SDL has worse latency and timing than ALSA, and there is also higher CPU usage.
The dummy sound driver allows compiling the emulator without sound support, but it still does synchronization to real time (unless no_sound=1 is used).
Fixed (hopefully) the problems with new ALSA versions. If it still does not work (crashes during sound initialization), adding -DUSE_OLD_ALSA_API=1 to the compiler flags may help.
ALSA sound device can be selected with the new 'snd_device=devname' option (this is ignored if SDL is used for sound playback).
Experimental support for DAVE clock frequency switching (BF register bit 1). Due to lack of documentation, this may not always work as expected, but does fix sound in some programs where the pitch was too high. In case of problems, this feature can be disabled with the 'enable_bf_bit_1=0' option.
Fixed LPIXEL video modes (typo in nick.c).
Reset now clears all DAVE registers (fixes occasional hang of emulated machine after reset).

Changes in version 1.2

Fixed CPU frequency bug; now the correct value for cpu_freq is about 4000000 and not something like 1250000 as in the previous version. Also more accurate CPU timing.
Saving files to tape now works (but needs using the low transfer rate (1000 bits/second) for reliability).
Several changes and fixes to tape utilities.
Buffer sizes for sound output (sndbuf_hw and sndbuf_sw) can be changed.
Sound can be disabled (no_sound=1) for running the emulator at full speed.
Configuration options can also be set from the command line, overriding settings in ~/.ep128rc.

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