How many were aware of the two PS1 GPU versions?
While many these days see things like PS4 Pro, and PS5 Pro, not many are familiar with the PS1 and it's silent upgrade. On launch in Japan, and the most earliest of US units (I think for the first year and a half?), they ran on a GPU that had some limitations. For example, shaded polygons that are textured, lose the 8-bit shading and therefore get treated with 5-bit shading (visible banding). They also ran on dual ported VRAM (2x 16-bit chips), whereas the later versions could shade entirely in 8-bit precision and used a single 32-bit SGRAM video memory IC. The early GPU was also slower at alpha blending, but *faster* at blitting, making it a little better with the 2D games, but not so much with later PS1 releases with a lot of alpha blending such as FF8.
I'll attach a picture to show the differences. Monsters Inc. Scream Team, and Tomb Raider are good games to check the GPU revision as the banding is just so obvious in them.
Left is an original PS1 revision A GPU, whereas the right picture is from my SCPH-5501 (the later revised GPU).
Another slight fact, is that if you get a very early launch SCPH-1001 prior to Christmas of '95, don't be surprised if the picture is slightly darker. It's actually not a fault of the hardware, but a bug in the boot ROM (this would be version 2.0 for the US release), as it accidentally is using NTSC-J's 0 IRE, not the NTSC-M 7.5 IRE standard. This was rather quickly fixed by Christmas with a patched boot ROM.
MB Microvision Console [EU]
(I should mention, both pictures are not from the same TV/monitor. Left was from my TV, right was from my computers monitor using a RetroTink and apparently forgot what focussing was.)