Discussion
Many people know that regular x86 AMD CPUs have a secondary CPU for management tasks called PSP, which is an ARM CPU.
Today I learned:
The System Management Unit (SMU), which is responsible for controlling the power delivery, current limits, temperature limits, etc. is ... Xtensa!
So that's yet another fun CPU core inside your "CPU" 😹 !
I wonder if there are any other cores in there...
@manawyrm i would be shocked if there are not more.
I mean, not too long ago i was looking at i think a chip at work that had 40-something cores in it, all doing different things
@azonenberg well, today was the first time I had to look into the SMU firmware to force an unstable mainboard into behaving properly.
Haven't had to abuse the PSP like that (yet).
Already quite interested to see what's next in this chain^^ :D
@manawyrm i mean on one of my boxes...
Everything in the main xeon and pch
Gpu management processor
Ssd controller
NIC
Those are the easy ones
But many of those probably have a lot of extra cores too.
And then the ast2500 has an arm11 main processor and there's probably some extra cores inside that too
@azonenberg the AST2500 is suuuch a fun chip with soo many absolutely cursed features. Have you read its datasheet?
Between the ability to receive/send arbitrary PCIe TLPs, their UART memory read/write 8051 and the internal JTAG controller that can be routed to the ARM11 itself and also externally, I really like these funky chips 😁 😁
(but OH GOD are they a security catastrophe!)
@manawyrm there's a reason i don't connect ipmi on any of my machines except if I'm specifically fixing a boot issue I can't deal with any other way
@azonenberg@ioc.exchange @manawyrm@chaos.social honestly not convinced you're any more secure by not plugging a network caple into them given all of their hooks into the system and NICs
@erincandescent @manawyrm i *think* it's fully offline but who knows.
I haven't been able to find xeon scalable boards without bmcs, if i could i would
@manawyrm@chaos.social Who provides AMD's DDR 4 & 5 controllers? Normally there's a core from the vendor of those hidden inside. Famously for Synopsys' DDR4/5 controllers this means an ARC