| 9 Jul 2025 |
 zimward | also: has anyone used the advertised TPUs of those chips? basically any new one advertises them (supposedly to make investors happy ig) but i never saw any real use of them | 10:05:47 |
 dramforever | most would do, SG2042 is ... weird | 10:07:13 |
| dramforever | but it is the most powerful one we have now | 10:07:59 |
| dramforever | so my main point is that i think we should skip sg2042 | 10:08:14 |
| dramforever | eic7700x should be pretty good apart from only having 4 cores | 10:08:34 |
| zimward | its the first real server grade riscv chip we have so far (atleast spec-wise), if you can share any experiences whats wrong with it i would appreciate it as i never got the opportunity to play with one. that being said im not opposed to throwing 20 4-core SoMs in a cluster | 10:10:33 |
| dramforever | i don't know how much i can share but it is a really scuffed chip | 10:15:08 |
| dramforever | ghostwrite is just the most well known of all problems | 10:18:41 |
| dramforever | and i'll just say turning the non-compliant vector extension off is almost a trivial workaround | 10:19:50 |
| zimward | its a bug in silicon. there is just no other workaround lol | 10:20:43 |
 Alex | Yikes. Did they not do enough test simulations while designing the core? | 10:21:50 |
| zimward | no differential fuzzing atleast | 10:22:06 |
| dramforever | what do you simulate? | 10:22:11 |
| dramforever | but also there's two teams involved, the now-called xuantie that made the c920v1 cores, and the sophgo team the made the whole processor by slapping together 16 of 4 core clusters | 10:24:09 |
| dramforever | this ... did not go particularly well | 10:25:38 |
| dramforever | oh, i remembered something i can share: LLVM-compiled multi threaded programs may run very slowly because fence(acq_rel) is compiled to fence.tso | 10:26:41 |
| dramforever | which the cores raise an illegal instruction exception due to a misunderstanding in the specs | 10:27:02 |
| Alex | So the system has to context switch on most fences?
Pure pain. | 10:27:55 |
 Steven Keuchel | I have both the pioneer (sg2042) and the megrez (eic7700x). the c920 cores in the sg2042 are kinda slow. too slow to use as a desktop. and a lot of processes swamp the memory subsystem. the p550 are already much faster. I would estimate that 4x eic7700x might outperform the sg2042, and would probably also be cheaper. | 10:28:36 |
| dramforever | not most fences, just this specific one | 10:28:38 |
| dramforever | just randomly fences taking hundreds of cycles | 10:28:53 |
| dramforever | but it is every time it executes | 10:29:04 |
| Alex | Ah, I'm not very familiar with LLVM's multithreading primitives... | 10:29:12 |
| dramforever | so gcc can do -mno-fence-tso | 10:30:02 |
| dramforever | but i don't think llvm is getting that any time soon, or ever | 10:30:11 |
| zimward | fun stuff. but sounds like it should be an issue in all C920v1 cores | 10:50:04 |
| dramforever | yes | 10:52:34 |
 Tristan Ross | In reply to @skeuchel:matrix.org
I have both the pioneer (sg2042) and the megrez (eic7700x). the c920 cores in the sg2042 are kinda slow. too slow to use as a desktop. and a lot of processes swamp the memory subsystem. the p550 are already much faster. I would estimate that 4x eic7700x might outperform the sg2042, and would probably also be cheaper. Matthew Croughan has a P550 and I've tried compiling things on it. We've seen a lot of things fail on it which makes me think there's something wrong. How does it perform for you? | 13:52:33 |
| dramforever | In reply to @rosscomputerguy:matrix.org
Matthew Croughan has a P550 and I've tried compiling things on it. We've seen a lot of things fail on it which makes me think there's something wrong. How does it perform for you? fail as in...? | 13:59:50 |
| dramforever | random userspace crash? | 13:59:55 |
