I don't see why 700mhz wouldn't be enough. I've run vista on an amd k6-2 500mhz wif 256MB ram and it ran fine but slowly.
AMD Phenom II x6 1045T @ 2.7 Ghz
8GB Corsair Vengeance Ram
Crucial M500 240GB SSD (boot drive)
500GB WD 5000AAKX-001CA0
1.5 TB Seagate ST1500DM003
Zotac Geforce GTX 950 2GB GDDR5
Windows 10 Pro 64 bit