One of them includes the old EE and GS chips, and the other contains the newer unified EE+GS chip, otherwise being identical.
Sony also advertised heavily as well and it had the advantage of being supported by Electronic Arts.
Not only did Sony roll out the PS2 online adapter in late 2002 to compete with Microsoft, several online launch games were first party titles such as SOCOM US Navy SEALS in order to show that Sony was supporting this feature actively.
It is widely believed that Sony has abandoned support for the hard drive.
During one week in November, sales in the entire country of Britain totalled 6,000 units - compared to 70,000 a few weeks prior.
These included a PCMCIA slot instead of the Expansion Bay (DEV9) port of newer models.
Hardware sales remained strong until 2004 saw the console apparently approaching saturation point.
A product named HD Connect can be soldered into the unit giving hard drive support though.
Although Sony placed little emphasis on online gaming during its first year, all that changed because of the launch of the online-capable Xbox.
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For some consumers this is in fact a limitation, especially for the fans of titles such as Final Fantasy XI, which requires the use of this peripheral, and prevents the use of the official PS2 Linux kit.
However the New Slim Silver Models have more issues with playing PlayStation games than the first PS2 revisions.
It also has a different lens and some compatibility issues documented by Sony for earlier PS2 games.
The PS2 launch seemed unimpressive and gaffe-prone, compared to the well-planned launch of the Sega Dreamcast, which was making a genuine attempt to woo developers and which had better launch titles.
This led to further shortages, and the issue was compounded in Britain when a Russian oil tanker became stuck in the Suez Canal, blocking a ship from China carrying PS2s bound for the UK.
When the PlayStation 2 launched in Japan in March 2000, Sony sold 980,000 units over the opening weekend.