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Overview
Comment:Moved the "TC08 vs TD8E" and "V3D vs V3F" text from the ChangeLog.md file to the wiki, and referenced it from the ChangeLog.
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SHA3-256: 01e0bc0d695bf20faba94d030fd6be27d8f205f8da85a70594f497b4625a0048
User & Date: tangent 2019-02-12 05:53:49
Context
2019-02-12
06:13
Updated ChangeLog.md to cover new CC8 work check-in: 1992d9b147 user: tangent tags: trunk
05:53
Moved the "TC08 vs TD8E" and "V3D vs V3F" text from the ChangeLog.md file to the wiki, and referenced it from the ChangeLog. check-in: 01e0bc0d69 user: tangent tags: trunk
05:15
Clarified the tail end of the concrete memory map example in the CC8 user manual. check-in: 3f8a6d035d user: tangent tags: trunk
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Changes to ChangeLog.md.

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    *   Replaced the hand-maintained `media/os8/os8.tu56` OS/8 V3D TU56
        tape image used by boot option IF=3 with an `os8-run` script
        that's run at build time to generate a series of four similar
        tape images from pristine, curated source media, just like
        we did for the RK05 media in the prior release.

        These four tapes are the result of a 2×2 matrix of choices
	between which virtual DECtape hardware (TC08 or TD8E) and
	which OS/8 version (v3d or v3f).

	__TD8E versus TC08__

	The previous os8.tu56 was a an image created from a DECtape
	found running on someone's PDP-8 system.  That system had
	a TD8E "Simple DECtape" controller that required the CPU
	to monitor the tape as it sped past the heads, and transferred
	data through the AC, not by using Direct Memory Access.

	Most surviving PDP-8e hardware has that single-card DECtape
	controller.  However there is another controller available
	for the PDP-8, the TC08 which offloads to hardware more of
	the tape motion, and uses DMA to transfer data.  Before the
	advent of the PDP-8 OMNIBUS, TC08 was the only controller
	option available.  But it was expensive.

	Here's where the interesting tradeoff comes from:  Emulating
	a DMA device in SIMH is quick and easy.  Your driver gets
	the pointer to the blocks and copies them.  The TCO8 emulator
	for SIMH is simple and runs as fast as a byte copy.

	Emulating the TD8E is harder.  You listen for the commands
	to start the tape moving, and then for the desired block
	number.  Then you wait for each 12 bit word to go into that
	block to come to you through the emulation of a programmed
	I/O instruction that put that word in the PDP-8 AC.

	If all you ever want to do is play with DECtape under SIMH,
	choose the TC08 device. It's a LOT faster. However if you
	are using SIMH and the PiDP-8/i to create TU56 images for
	use on real hardware, you may want to choose TD8E, because
	it's the more commonly found DECtape controller.

	__OS/8 V3D versus V3f__

	OS/8 version 3D is the release most commonly found in the wild.
	There was additional development of OS/8 to support such things as:
	*   a bigger memory address space on the PDP8a hardware
	    (the successor to the PDP8e).
	*   new devices such as the double density RX02 floppy and
	    the RL02 cartridge disk drive.
	*   Additional bug fixes, and enhanced functionality.
	*   Ports to new hardware such as the VT78 word processing system.

	The device drivers were made available as the "OS/8
	Device Extensions Kit."

	Eventually the separately sold FORTRAN IV, MACREL, and BASIC
	language packs, the Device Extensions and all known bug fix
	patches were integrated into one product sold as the "OS/8
	Combined Kit."  But by that time, very few customers were
	interested in paying for such an incremental update, and there
	were very few new OS/8 customers buying new hardware and spending
	the big bucks for a source license.

	Although images of pristine OS/8 v3d distribution media kits
	for both source and binary have long been available if you knew
	where to look, the "Combined Kit" was thought to have been lost.

	A snapshot of most of the sources of the V3D Device Extensions
	Kit was available in the internet as a self-extracting archive
	os8v3f.exe.  When fear of executables with malware took hold,
	this archive was nearly lost as it was purged from various
	PDP-8 software archive sites.

	Heres's the exciting bit:

	The os8v3f.exe archive was found, and is in the process of being
	assembled integrated and validated.  That work is documented in
	os8-v3d-device-extensions.md. The v3f choice you make gives you a
	bootable TU56 image with the OS/8 Device Extensions.  It is required
	if you care to work with rx02 floppy disk images.

	VERY recently, we've connected up with folks who have made
	significant progress recovering source and binary of the OS/8
	Combined Kit.  If all goes as planned, the next OS/8 packs
	after this release will contain that kit.

	The primary driver in the development of the os8-run scripting
	language was to make it easy to build OS/8 from source that would
	be managed ina modern source code enviornment but then to generate
	system images in arbitrary formats with arbitrary configurations
	and contents.

	The 4 tu56 images:

	V3D TC08
	V3D TD8E
	V3F TC08
	V3F TD8E

	are the result of this work.

        *   You can ask to have the IF=3 boot option use the OS/8 V3F
            tape instead of the OS/8 V3D default.  Both versions get
            built, always, but only one gets to be the boot tape for
            this option.  This may be the first time that V3F was
            ever easily available to SIMH users.  Previously, you
            had to assemble it from pieces found all over the Internet.

            TODO: Briefly list the differences between V3D and V3F.

            (Bootable V3F RK05 media are planned for a future release.)

        *   You can also select whether the IF=3 boot option uses
            the boot tape configured for a PDP-8 with the TD8E tape
            controller instead of the default, which assumes a TC08.
            The prior release was hard-coded for the TD8E.

................................................................................
    make the GPIO stuff work at all yet.  For now, it just lets this
    software be used on your FreeBSD desktop or server machine.  It may
    allow building on other BSDs, but that is untested.

*   A year of maintenance and polishing, much of it resulting in
    documentation and build system improvements.

[pv]:  https://tangentsoft.com/pidp8i/doc/trunk/README.md#systemd




<a id="20171222"></a>
## Version 2017.12.22 — The "Languages and Custom OS/8 Disk Packs" release

*   All prior versions of the PiDP-8/I software distribution included
    `os8.rk05`, a "Field Service Diagnostic" OS/8 disk pack image with







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    *   Replaced the hand-maintained `media/os8/os8.tu56` OS/8 V3D TU56
        tape image used by boot option IF=3 with an `os8-run` script
        that's run at build time to generate a series of four similar
        tape images from pristine, curated source media, just like
        we did for the RK05 media in the prior release.

        These four tapes are the result of a 2×2 matrix of choices
        between which virtual DECtape hardware ([TC08 or TD8E][tctd])
        and which OS/8 version ([V3D or V3F][v3df]):





























































































        *   You can ask to have the IF=3 boot option use the OS/8 V3F
            tape instead of the OS/8 V3D default.  Both versions get
            built, always, but only one gets to be the boot tape for
            this option.  This may be the first time that V3F was
            ever easily available to SIMH users.  Previously, you
            had to assemble it from pieces found all over the Internet.



            (Bootable V3F RK05 media are planned for a future release.)

        *   You can also select whether the IF=3 boot option uses
            the boot tape configured for a PDP-8 with the TD8E tape
            controller instead of the default, which assumes a TC08.
            The prior release was hard-coded for the TD8E.

................................................................................
    make the GPIO stuff work at all yet.  For now, it just lets this
    software be used on your FreeBSD desktop or server machine.  It may
    allow building on other BSDs, but that is untested.

*   A year of maintenance and polishing, much of it resulting in
    documentation and build system improvements.

[pv]:   https://tangentsoft.com/pidp8i/doc/trunk/README.md#systemd
[tctd]: https://tangentsoft.com/pidp8i/wiki?name=TD8E+vs+TC08
[v3df]: https://tangentsoft.com/pidp8i/wiki?name=OS/8+V3D+vs+V3F


<a id="20171222"></a>
## Version 2017.12.22 — The "Languages and Custom OS/8 Disk Packs" release

*   All prior versions of the PiDP-8/I software distribution included
    `os8.rk05`, a "Field Service Diagnostic" OS/8 disk pack image with