Hardware of each VM:
Memory: 521MB
Processors: 1
Hard Disk (SCSI): 30 GB
Network Adapter: NAT
USB Controller: Present
Display: 1 monitor
This is the default config I believe. I downloaded this one:
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But now, I am not sure which one I downloaded... I think it was the "Aimed for compatibility (10 GB)", but anyway... try this one, and if it still doesn't work, you should try the other one.
You also need a good comp... I mean, you can't be running a lot of VM without a good computer... I guess my specs are so good...
The most important thing is RAM, but also the Processor...
I have i7-6700 @ 3,40Ghz, 16GB RAM, and well my graphic card is a NVidia GeForce GTX 960, which is not bad and it will help a bit too.
Oh btw I forgot the MOST IMPORTANT THING EVER, the Hard Drive. It MUST be SSD. And the virtual machines should be on the SSD (Logic).
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You just need to add 1 VM, then you create-clone them by right-clicking your VM, Manage --> Clone --> Next --> Create Linked Clone. So this way you have 1 "original" VM and then 5-6 "Linked Clones"
Oh and btw, Not sure if it matters but I am using VMware Workstation 12 Pro. Version 12.1.0 build-3272444