SIMH - Revision history

Vaxorcist: /* SIMH Flavors */ Update current SimH Classic version

2026-09-08T15:46:51Z

SIMH Flavors: Update current SimH Classic version

← Older revision		Revision as of 15:46, 8 September 2026
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	It is relatively hard for a beginner to decide which way to go. I will not give any specific advice, but some short descriptions:		It is relatively hard for a beginner to decide which way to go. I will not give any specific advice, but some short descriptions:

	'''SimH Classic''' is the oldest one, whereof the others were forked later on. It is Bob Supnik work mostly, except for some HP simulators. Development apparently stopped (or at least slowed down) in December 2022. The current version is SIMH V3.12-3.		'''SimH Classic''' is the oldest one, whereof the others were forked later on. It is Bob Supnik work mostly, except for some HP simulators. Development apparently stopped (or at least slowed down) in December 2022. The current version is SIMH V3.12-5.

	'''"New" SIMH''' was the first bigger fork and added a lot more simulated computer systems.		'''"New" SIMH''' was the first bigger fork and added a lot more simulated computer systems.

Vaxorcist: Vaxorcist moved page SIMH/Draft to SIMH: Distinction between SimH variants

2026-09-08T15:44:16Z

Vaxorcist moved page SIMH/Draft to SIMH: Distinction between SimH variants

← Older revision		Revision as of 15:44, 8 September 2026
(No difference)

Vaxorcist: /* SIMH Flavors */ another "SimH Classic" in the text

2026-09-08T07:34:52Z

SIMH Flavors: another "SimH Classic" in the text

← Older revision		Revision as of 07:34, 8 September 2026
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	It is relatively hard for a beginner to decide which way to go. I will not give any specific advice, but some short descriptions:		It is relatively hard for a beginner to decide which way to go. I will not give any specific advice, but some short descriptions:

	'''"Classic~~" SIMH~~''' is the oldest one, whereof the others were forked later on. It is Bob Supnik work mostly, except for some HP simulators. Development apparently stopped (or at least slowed down) in December 2022. The current version is SIMH V3.12-3.		'''SimH Classic''' is the oldest one, whereof the others were forked later on. It is Bob Supnik work mostly, except for some HP simulators. Development apparently stopped (or at least slowed down) in December 2022. The current version is SIMH V3.12-3.

	'''"New" SIMH''' was the first bigger fork and added a lot more simulated computer systems.		'''"New" SIMH''' was the first bigger fork and added a lot more simulated computer systems.

Vaxorcist: /* SIMH Flavors */ "SimH Classic" now

2026-09-08T07:33:00Z

SIMH Flavors: "SimH Classic" now

← Older revision		Revision as of 07:33, 8 September 2026
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	For some time passed there are three flavors of SIMH now:		For some time passed there are three flavors of SIMH now:

	* [["Classic~~" SIMH~~]] ([http://simh.trailing-edge.com/ http://simh.trailing-edge.com/])		* [[SimH Classic]] ([http://simh.trailing-edge.com/ http://simh.trailing-edge.com/])
	* [["New" SIMH]] ([https://github.com/simh/simh https://github.com/simh/simh])		* [["New" SIMH]] ([https://github.com/simh/simh https://github.com/simh/simh])
	* [[OpenSIMH]] ([https://opensimh.org/ https://opensimh.org/])		* [[OpenSIMH]] ([https://opensimh.org/ https://opensimh.org/])

Vaxorcist: Warning about the minus character before the size of truncation

2023-04-07T10:16:50Z

Warning about the minus character before the size of truncation

← Older revision		Revision as of 10:16, 7 April 2023
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	Keep in mind that the <code>truncate</code> command truncates whatever file you specify, so look first if metadata is present.		Keep in mind that the <code>truncate</code> command truncates whatever file you specify, so look first if metadata is present.

			'''Another possible pitfall:''' <br>If you leave out the <code>-</code> (minus) before the <code>512</code>, you will end up with a corrupted image of 512 bytes only!

	'''Caution:''' <br>		'''Caution:''' <br>

Vaxorcist: Draft extended

2023-04-03T20:07:58Z

Draft extended

← Older revision		Revision as of 20:07, 3 April 2023
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	Networking is covered in the [[Networking with SIMH]] guide.		Networking is covered in the [[Networking with SIMH]] guide.

			[[Category: Emulators]]

			== SIMH Media Handling ==

			SIMH handles computer storage media in the form of data files called "images" for:

			* [[Punched card]]s
			* [[Paper tape]]s
			* [[DECtape]]s
			* [[Magnetic tape]]s
			* [[Disk]]s

			All of these image files are said to be interchangeable between the three SIMH flavors with one exception: Image files used with "New" SIMH may be unreadable with the other two flavors because of 512 byte of meta data appended to the standard SIMH images.

			Sorry, Windows folks, the next two commands are for [[Linux]] only! -
			If someone knows how to do the same in [[Windows]], please add it here.

			You can visualize the appended metadata under Linux with (example image file trek7.rk7):

			$ tail -c 512 trek7.rk7 \| hexdump -C
			00000000 73 69 6d 68 56 41 58 20 31 31 2f 37 35 30 00 00 \|simhVAX 11/750..\|
			00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \|................\|
			*
			00000040 00 00 00 00 52 4b 30 37 00 00 00 00 00 00 00 00 \|....RK07........\|
			00000050 00 00 00 00 00 00 02 00 00 00 d2 1e 00 00 00 02 \|................\|
			00000060 4d 6f 6e 20 41 70 72 20 20 33 20 30 39 3a 31 39 \|Mon Apr 3 09:19\|
			00000070 3a 32 34 20 32 30 32 33 0a 00 00 00 00 02 00 00 \|:24 2023........\|
			00000080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \|................\|
			*
			000001f0 00 00 00 00 00 00 00 00 00 00 00 00 fa 1e 03 18 \|................\|
			00000200


			In the metadata you can see:
			* the simulated computer model: <code>simhVAX 11/750</code>
			* the disk model: <code>RK07</code>
			* the time stamp: <code>Mon Apr 3 09:19:24 2023</code>

			The problem can be cured under Linux using (example image file trek7.rk7):
			$ truncate -s -512 trek7.rk7
			This truncates 512 bytes (the metadata) at the end of the image file.

			Keep in mind that the <code>truncate</code> command truncates whatever file you specify, so look first if metadata is present.

			'''Caution:''' <br>
			'''Truncating does not work with SIMH disk images in [[VHD]] format!!!'''

	[[Category: Emulators]]		[[Category: Emulators]]

Vaxorcist: Draft of the new generic SIMH page

2023-04-03T06:28:55Z

Draft of the new generic SIMH page

New page

'''SIMH''' consists of simulators for a lot of different machines, and as such, is a very important emulator for anyone interested in computer history; in particular, that of [[Digital Equipment Corporation|DEC]] systems, as the PDPs and even some [[VAX]] models are well emulated by it.

It can even emulate network interfaces for some of the simulated computers, e.g. the [[PDP-10]], [[PDP-11]] and VAX, so the emulated systems can network directly onto the [[Internet]], if the emulated operating system supports it, like BSD or [[VMS]].

SIMH was primarily written by Bob Supnik of [[Zork]] porting fame, and is now widely contributed to by others as well.

== SIMH Flavors ==

For some time passed there are three flavors of SIMH now:

* [["Classic" SIMH]] ([http://simh.trailing-edge.com/ http://simh.trailing-edge.com/])
* [["New" SIMH]] ([https://github.com/simh/simh https://github.com/simh/simh])
* [[OpenSIMH]] ([https://opensimh.org/ https://opensimh.org/])

It is relatively hard for a beginner to decide which way to go. I will not give any specific advice, but some short descriptions:

'''"Classic" SIMH''' is the oldest one, whereof the others were forked later on. It is Bob Supnik work mostly, except for some HP simulators. Development apparently stopped (or at least slowed down) in December 2022. The current version is SIMH V3.12-3.

'''"New" SIMH''' was the first bigger fork and added a lot more simulated computer systems.

'''"OpenSIMH"''' forked from "New" SIMH because of insurmountable different opinions of both maintainers and contributors.

== Usage ==

SIMH can either take in configuration parameters interactively, or you can store them in a file. If the file is the name of the emulator+.ini it will load them automatically (eg vax.exe loads vax.ini automatically). Once running, the CONTROL+E key will break the emulation and bring you back to the SIMH console where you can alter the running state.

Networking is covered in the [[Networking with SIMH]] guide.

[[Category: Emulators]]