[Simh] Way out idea for simh

[Ken Cornetet]

That “some kind of transfer utility” is exactly what I’m trying to implement.

In order to transfer files between a guest and host you need some sort of shared medium.

In the realm of simh hosted OSes, there are basically 3 forms of bidirectional io devices: paper tape, mag tape, and disk. Paper tape isn’t seekable, so it isn’t really suitable.

That leaves mag tape and disk as the only shared medium that is supported by the guest OS.

So the next question is, how do you implement a file transfer utility using shared tape or disk, and that’s exactly what I’ve proposed.

There is another option which can be used: modify the guest machine virtual architecture to implement a new data mechanism, and to the modify guest OS to support it. This has the advantage that it is more flexible and more powerful, but has the disadvantage of requiring not so trivial modifications of the guest emulation and modification to the guest OS. Additionally, since emulated machines have vastly different architectures, this would be difficult to generalize and integrate into simh as a whole.

I eventually plan to do exactly this on the hp2100 emulator by writing custom microcode (creating new instructions essentially) and writing an RTE driver so that userland applications can access it . However, the mods I make for the 2100 emulator will not be anywhere close to being usable on other architectures.

That’s the beauty of using the disk file as the shared medium – you modify simh once, and you get the ability to use that mechanism on every simh OS that knows how to handle raw disks or seekable tapes. You do have to write a small LIF interchange utility, but that shouldn’t be too bad.





From: Sampsa Laine [mailto:sampsa at mac.com]
Sent: Wednesday, April 20, 2016 2:01 PM
To: Ken Cornetet <Ken.Cornetet at kimballelectronics.com>
Cc: simh at trailing-edge.com
Subject: Re: [Simh] Way out idea for simh


On 20 Apr 2016, at 20:45, Ken Cornetet <Ken.Cornetet at kimballelectronics.com<mailto:Ken.Cornetet at kimballelectronics.com>> wrote:

Other than the OS on the old Atari 800 family of computers, I don’t know of any OS that supports a device to which you can supply a file name and then read or write data.

Most OSes view disk devices as a collection of blocks.


You’re missing my point - the guest OS would not be mounting this as a block device, but would have some kind of file transfer utility to talk to the host OS’s file system.

Sampsa



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