virtualbox.org

Wasn't sure where to post this. Hopefully the right place(if no please move).
I want to build a small server to run many VB's of old OS's (DOS/Early Windows(NT/2000/3.11/etc) Minix/etc/etc).
It will be used by one to three users for demo's basically I will login and set running demos.
Needs to be :
smallish (got to carry it!)
LOW POWER (need to be able to run from (via invertor if needed) batteries)
Cost is a big factor as i am retired and broke! lol
The idea is that the VM's are either up and running or to be started via script/SSH.
The loading on each VM will be low (demo of a typical windows 200 system etc) but for example NT system would have a few VM's running (PDC/DHCP/DNS/client/email/Database) all headerless.
Another use would be to(for demo) provide under SIMH or HERC mainframes (IBM 360 etc) with a rterminal or two attached.
No monitor or keyboard would normally be plugged in. I want to demo what a business system in days gone by would be like.
The idea is for a very portable setup to demo old OS's at events where there might be little or no mains power. Network would be via a small switch to some laptops/Raspberry PI's' (looking at the 400 with a low power monitor).
I started to think about it but not really sure.
So suggestions please?
Remember CHEAP, low power (nice if I can run it all day off a 110AH caravan battery).
Dos systems will run s some games/lotus 123/dbaseIII/wordstar style things but no graphics heavy modes)
I use linux as hosts and generally and suspect that would be the lightest host OS.
Alan

First I'd look for a computer that can run from a regular car. Laptops have add-on power supplies that can plug the laptop into a car's cigarette lighter / 12Vdc power plug. Avoiding inverters will increase efficiency. You can then plug the car supply into the battery instead.

A regular laptop will also have a keyboard and monitor built-in, which will make setup a whole lot easier, and you can simply close the laptop (with laptop OS power controls set to ignore the lid) then you have a keyboardless/monitorless server.

Get a refurbished laptop with a year warranty on it, then you're likely to get cheaper & still reliable hardware. (I have gone refurbished several times on computers ad have had no trouble: when the seller warrants for a year, it means they think the hardware is good.)

Get a laptop with an Ethernet port, and if you really want to look retro, put it in a cardboard box that is decorated to look like an old IMB mainframe. Couple of holes on the back, top and bottom, for air flow. Also get a reasonable SSD to replace the laptop's hard drive, if you can't find a refurbished laptop with an SSD already. SSD will save on power.

As for your other devices, nominal "12Vdc" from a battery is really 13.something when charged and down to 11 or 10 when fully depleted (full depletion will kill the battery, research how to protect the battery, too.) Most devices, even the ones that run from a 12Vdc wall wart, require steady power. You'll need a power supply that can take car power in and give steady 12V out for your switch, and another power supply that can drive your Raspberry Pi's at 5V, and something to run your monitors. An inverter for the monitors, switch, and Pi supplies might be OK, though it should be true sine wave not modified, or it might kill the devices' power supplies. See if car-power supplies for these devices are available, then run them from the battery too. Inverters will draw more power than necessary to go to 120Vac which then gets changed down to low-voltage DC again, meaning loss of efficiency and shorter battery life.