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Not exactly. While that may have been the case way back in the past when AMD APUs were designed as a homonegnous CPU-GPU unit from the start, I can tell you th
by ChuckNorris89 3y ago
Not exactly. While that may have been the case way back in the past when AMD APUs were designed as a homonegnous CPU-GPU unit from the start, I can tell you that's not the case with the relatively modern 5000 series.
I need to go in the Bios and specify explicitly how much of the system RAM I want allocated exclusively of the integrated GPU and the rest stays available for system RAM.
The reason is because Ryzen 5000 APUs seem to be a job rushed out the door so they're just a Zen 3 CPU with a separate Vega GPU glued together on the same die, but they're not a homogenous design, designed to work as one unit, like the APU of the PS5, so memory wise they're unaware of each other, even though AMD calls them APUs, they're not really, but more like separate CPU and GPU on the same die.
I wish I knew about this limitation at the time, as Intel chips with integrated graphics have unified memory.
- yjftsjthsd-h 3y agoI wonder if a clever enough driver+firmware could make that hot-adjustable (or truly unified, rather) with nothing but a software patch. It sounds like the pieces are all there.
- sgtnoodle 3y agoMy understanding is that the Steam Deck, which uses a Zen 2 APU, dynamically allocates system RAM to VRAM. It only works in SteamOS (Arch Linux) though. Folk that run Windows on their Steam Decks need to go into the BIOS and bump the static mapping to 4GB in order to get good performance in many games.
- AnthonyMouse 3y ago"Unified" doesn't mean the CPU and GPU can store different data in the same memory at the same time. The BIOS setting is just assigning how much are visible for each to use in the absence of OS support for doing it dynamically. Clearly if you can change the amount it isn't a hardware limitation, and I'm not even sure if it needs some special support. The iGPU surely supports DMA, so if it does a load from memory "assigned" to the CPU does it perform any differently than from memory "assigned" to the GPU?
- fulafel 3y agoSorry but this sounds like jumping to conclusions, going off only the fact that you can fence off some memory in the BIOS. See eg this windows gaming site review where they couldn't find a difference in the performance between allocating 64MB or 2GB save for satisfying some games that need to detect a certain amount of GPU memory to start: https://www.techspot.com/article/1578-amd-raven-ridge-reserved-memory-explainer/ https://www.techspot.com/article/1578-amd-raven-ridge-reserv... But I don't doubt there still exist software (Firmware, OS, driver, graphics API) problems where unified memory ends up being used badly. There doesn't seem to be evidence that much if any of it are because of hw limitations.