As of V4 everything was unified into one board, except the power supply.
However the New Slim Silver Models have more issues with playing PlayStation games than the first PS2 revisions.
Yet, the PS2 initially sold well solely on the basis of the strength of the PlayStation brand and its backwards compatibility, selling over 900,000 units in the first weekend in Japan.
The PS2 also supports PS1 memory cards (for PS1 game saves only) and controllers (the PS2's Dual Shock 2 controller is essentially a slightly upgraded PS1 Dual Shock).
It also has a different lens and some compatibility issues documented by Sony for earlier PS2 games.
PS2's opening day console sales eclipsed the previous record of 225,000 made by the Sega Dreamcast in 1999.
Later hardware revisions had better compatibility with PlayStation games (Metal Gear Solid: VR Missons works on most silver models).
Developers also complained that it was difficult to develop for the system, with little in the way of reference material from Sony for its exotic architecture.
However the New Slim Silver Models have more issues with playing PlayStation games than the first PS2 revisions.
In preparation for the launch of a new, slimmer PlayStation 2 model (SCPH-70000), Sony had stopped making the older PS2 model (SCPH-5000x) sometime during the summer of 2004 to let the distribution channel empty out stock of the units.
This allowed the PS2 to tap the large install base established by the PlayStation.
