[Simh] SIMH and physical hardware

[Armistead, Jason BIS]

On 2/9/16 11:41 PM, Zachary Kline wrote:
> This is around 50% humorous, but it’s still a thing I’ve been thinking about lately. From a newbie’s perspective, all SIMH machines are very similar. The worst thing about emulation is that the “feel,” of the original hardware doesn’t seem to be there. Simh can emulate tons of hardware from different manufacturers, but none of that will tell me what it was like to actually use the devices in a physical sense.
> As a blind user, I’m doubly interested in this kind of physicality because I experience the world through touch and sound. I have little conception of the shape or size of many of these notional machines, and they are all reduced to various abstractions at a console prompt. It’s hard to imagine a thing I was far too young to experience.
> I was reminded of an Apple II emulator I saw once, sadly not accessible, which made the appropriate disk drive noises in use. Its kind of useless from a  practical standpoint, but a lot of my interest in these machines isn’t practical to begin with. I want to explore an earlier kind of computing, but don’t expect to get a job with it or have anything beyond some entertainment.
> I really don’t know what, if anything, can be done to bridge this weird disconnect. Actual hardware is probably gradually fading out, and in any case probably wouldn’t be accessible from my perspective anyway.
>
> Any thoughts? Apologies for the disjointed post, it’s rather late. ;) 

Others have mentioned the familiar sound of disk drives and other devices.  In the world of SIMH, if the emulated system is running at a higher speed than the original hardware, the access times of such devices is also reduced (possibly quite significantly).  So what might have once been the slow clack-clack sound of floppy drive heads being stepped into position or recalibrated back to track zero, now becomes a much faster, higher-pitched sound.  Unless the simulated I/O device response timing matches that of the original hardware it emulates, attempting to play back recordings from physical hardware based on when and how SIMH access that device would be impossible to achieve, or be completely unsynchronized, or would need to be sped up, resulting in a "Vintage Computing meets the Chipmunks" sound !

PS: I always remember the sounds of an RD54 disk buzzing to life during the boot sequence of our trusty MicroVAX 2000, and the TK50 tape leader being picked up by the drive mechanism when first loaded.

Just my $0.02 worth
Jason