Mentec M1 PDP-11 CPU

[gslick]

Does anyone know much about one of these Mentec M1 PDP-11 CPUs, or ever used one?

http://www.ebay.com/itm/141048412486

I'm curious about the seller's description that it doesn't have FPU support. That seems like a major issue for full compatibility with all PDP-11 OS.

For example, I have one of these QED-993 CPUs which also lacks FPU support and I was never able to get 2.11BSD to run on it since 2.11BSD assumes that a J11 processor has FPU support.

http://www.ebay.com/itm/200600166676

An old copy of the Mentec page on the M11 says that it supports the FPU with microcode revisions 2.0 or later. I wonder if that is also the case with the follow on M1 ASIC re-implementation of the M11 and if some versions of the M1 microcode do not include FPU support and some versions do.

http://web.archive.org/web/20060324070926/http://www.mentec-inc.com/m11specs.htm

 

[AK6DN]

Does anyone know much about one of these Mentec M1 PDP-11 CPUs, or ever used one?

I'm curious about the seller's description that it doesn't have FPU support. That seems like a major issue for full compatibility with all PDP-11 OS.

For example, I have one of these QED-993 CPUs which also lacks FPU support and I was never able to get 2.11BSD to run on it since 2.11BSD assumes that a J11 processor has FPU support.

2.11BSD for the PDP-11 has a patch (#445) that is supposed to fix the problem with the kernel resident s/w fpu emulator for systems without h/w fpu. I have no idea if this patch would remedy the issue of running 2.11BSD on your J11 without FPU, but at least from the description it should.

Don

Header from patch 445 file:

Subject: kernel floating point simulation crash, postscript printer Makefile update
Index:	sys/pdp/mch_fpsim.s,local/mp/Makefile 2.11BSD

Description:
	The in kernel floating point emulator, used when no hardware FP unit
	is present, would panic the system on the first FP instruction
	executed by a user program.

Repeat-By:
	Try to run a program using FP on a system w/o hardware FP
Fix:
	Apply the patch below and rebuild the kernel.

	Also included in the patch is an update to the 'mp' Makefile.  This
	had been completed several years ago but never posted.

 

[gslick]

It has been a while since I last gave 2.11BSD a try on the QED-993. I did see that patch and rebuilt the kernel with that patch applied but didn't really get any further in the boot process after that. Since the source is all available I could try to track down further what is going wrong. I wasn't sufficiently motivated to try to do so at the time and was disappointed with the OS compatibility of the QED-993.

I was wondering if the Mentec M1 would have better compatibility with various PDP-11 OS flavors. If it also has issues running 2.11BSD it wouldn't be very interesting to me.