[j_seigh]

The comments about HFT needing tightly synchronized clocks got me thinking.

Back in the day, way back in the 80's, IBM replaced the VM with VMXA. VM could trap and emulate all the important instructions since they were privileged instructions except one, the STCK (store clock) instruction. So virtual machines couldn't set their virtual clocks so they were always in sync. VMXA used new hw features that let you set the virtual clock. You could specify an offset to the system clock. But some of IBM's biggest customers depended on all the virtual machines clocks always being in sync. So VMXA had to add an option to disallow setting the clock for specified virtual machines.

Except all of development knew how trivial it was to trap or modify the STCK's to produce a timestamp of you choosing. This was before it was common knowledge the client code should never be trusted. But nobody enlightened IBM corporate management. It was a serious career limiting move at IBM. It didn't matter if you were right. So I'm pretty sure some serious fortunes were made as a result.

So the question for HFT is; are they using and trusting client timestamps, or are the timestamps being generated on the market maker's servers? If the latter, how would the customer know?