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In earlier years, it was common for DRAM chips to be one bit wide, so that an 8-bit machine would use eight of them to form one memory bank. Occasionally, 4-bit-wide chips would be used, e.g. the later models of the Commodore 64 used a pair of 64kbitx4 chips for 64Kbyte.

Looking at the mainboard of the PlayStation 1, which I believe was a 32-bit machine, it seems to have only something like four RAM chips. Were they 8 bits wide? Or even wider?

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    Does your question apply to all revisions ? I only ask as I (cannot check at moment, using mobile) have a -vague- thought the later slimmer smaller ps1 "PS-One" had a slightly updated and revised board layout. Not suggesting this meant differing chips but... The "real" one I mean that is, not that curious newish emulated box-o-tricks. – AndyF Jan 29 at 13:06
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    @AndyF I was thinking of the original version, but also curious if the answer changes in a later version! – rwallace Jan 29 at 13:14
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    Fair enough ;) As I say I cannot look at the moment sorry, but genuinely thought the extra "also about" was worth mentioning on a comment. :) – AndyF Jan 29 at 13:18
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    Completely askew: the Acorn Electron uses four 64x1 DRAMs, mapping each CPU access to two RAM accesses. And that's partly why its RAM access is, at its fastest, half the speed of that of a BBC Micro. – Tommy Jan 29 at 16:26
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    @Tommy That's a good pic, and probably the right one! I've added it, and some explanation of it, to my answer. According to the service manual, the DRAMs are KM48V514BJ-6-TEL. – cjs Jan 30 at 6:16
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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 IO0 through IO7; these are connected via bus lines CPH00-CPH31 to the DD0-DD31 pins 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.

PU-18 board photo

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 board.

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).

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