Technically, within the language, yes. C itself simply delegates a lot of logic to the "physical machine"[1] by leaving it unspecified or implementation-defined. In contrast, Haskell actually tries to model these differences within the type system and standard libraries, with IORefs, STMs, and whathaveyou.
(In fact, I just checked the IORef documentation and it actually references the x86/64 architecture manual to explain some of the behaviour that can be expected. I would be surprised if any part of the C standard did that.)
[1]: I mean, if we're using an x86 derivative we're still talking about a very fancy PDP-11 emulator.
I see. The language spec explicitly talks about the machine. That's not nothing.
In practice, though, when I have some piece of memory-mapped hardware attached, and I want to talk to it, in C I can say:
*(uint32_t*)0xF00BA4 = 0x0102ABCD;
or whatever I need to flip the bits. C lets me actually control the whole machine. Whereas Haskell... I don't know, but I suspect it lets me actually use the physical machine a lot less.
(In fact, I just checked the IORef documentation and it actually references the x86/64 architecture manual to explain some of the behaviour that can be expected. I would be surprised if any part of the C standard did that.)
[1]: I mean, if we're using an x86 derivative we're still talking about a very fancy PDP-11 emulator.