Yes, the PlayStation 1 CPU had a 32-bit data bus, and RAM was always
32 bits wide, spread over one or more chips.
However, there were at least three major revisions of the Playstation
1 hardware and more than half a dozen different mainboards spread
across a lot of different models.
Information on the earlier models is hard to find. The GameSX wiki
schematics:console_related_schematics page has service
manuals for the 5500, 7500, 9000 and 101 (PSOne) series, but nothing
for the earlier 1000 and 3000 series consoles.
The 5500 series uses 4 × 8-bit-wide DRAM chips, IC106 through IC109 in
the service manual (PDF), as can be seen on pages 23 and 24 of
the scan (PU-18 board 1/5); the chips are at grid references B2
through I2. (The RAM data pins are labeled
are connected via bus lines
CPH31 to the
of the CPU.)
This appears to be the board for which Tommy found a photo;
you can see "PU-18" written large in the centre and the four RAM chips
at the left, with adjacent matching IC numbers.
The data I/O for the RAM are on pins 2-5 and 24-27 of the 28 pin
package. They're second through fifth pins from the top on either side
of the package in this photo, and you can clearly see traces from pins
24-27 of each chip leading to the data bus pins on the left side of
the CPU, and in between those groups of four, groups of four vias
adjacent to the CPU for pins 2-5, routed on the other side of the
I am guessing that the board of the PlayStation you were examining
looks much like this.
The 7500 series (service manual PDF) changed to use a single
32-bit wide 16 Mbit DRAM (IC106).