You are probably reading this on some kind of portable computer. But let's go back to late 1987 where Amstrad turned their highly successful PC 1512 and 1640 into portable PC's. Yes, for as little as £399 + VAT you could be typing in Wordstar on a train running from battery. But was the PPC 640 a white elephant or was it actually any good? ChinnyVision finds out.