User:Tom94022/ArealDensity

NOMINAL CASE
		Date	Areal Density
	RAMAC	1956	2.00E-06
	Toshiba MK2035GSS	2006	1.79E+02
		Gain	89,400,000
		CAGR	44.2%
WORST CASE
	RAMAC	1956.42	2.00E-06
	Toshiba MK2035GSS	2006.66	1.79E+02
		Gain	89,400,000
		CAGR	44.0%
BEYOND WORST CASE
	RAMAC	1956.01	2.00E-06
	Toshiba MK2035GSS	2006.99	1.79E+02
		Gain	89,400,000
		CAGR	43.2%

Actual AD data points (unlike those derived from Whyte) have known and small uncertainties. Generally the density itself is quoted by the vendor in three or four digits implying an uncertainty of +/- 0.5 digit. There can be uncertainty in the date associated with the availability of a specific AD in a production product. Generally this is counted at first customer shipment of a production HDD.

• With regard to the base point, the shipment of a production RAMAC there is no uncertainty in the AD, it is precisely 2.000 E-06 Gbit/in² to as many zeros as necessary. The first shipment of production model has a great deal of uncertainty; most accept the official IBM announcement on Sept 14, 1956 as the base date since there were already prototype units installed at Zellerbach and elsewhere. The earliest possible date would be the shipment to Zellerbach in June 1956. On the other hand production units were announced to be available in the middle of 1957 so latest possible date could be August 15, 1957.
• It is clear from multiple sources that the AD growth rate slowed in the middle of the first decade of this century. 2006 is also the 50^th anniversary of the RAMAC announcement. The state-of-the-art areal density is at least that of the Toshiba MK2035GSS at 178.8 Gbit/in² announced June 5, 2006 for delivery in August 2006. The uncertainty in areal density is at most +/- 0.03% and is negligible. The nominal shipment date is August 15, 2006 with an early date of August 1 and a late date of August 31.

To the right are three calculations of AD CAGR from RAMAC shipment until 2006, the nominal case, the worst case and a beyond the worst case. From the shipment of RAMAC to 2006 the ratio of areal density is highly certain at 89,400,000 and is the same in all three cases. The Nominal Case uses the nominal dates disclosed above while the Worst Case uses the early RAMAC date and the late Toshiba 2006. date. To test the limits a Beyond Worst Case was calculated assuming the RAMAC shipped very early in 1956, while the 2006 AD was not achieved until the end of 2006.