> Also, AFAIK on ARM the parts where CPUs integrate with the rest of the hardware are custom. The important thing for servers, disk and network I/O differs across ARM chips of the same ISA. Linux kernel abstracts it away i.e. stuff is likely to work, but I’m not so sure about performance portability.
Indeed. But Intel Xeon + Intel Ethernet integrates tightly and drops the Ethernet data directly into L3 cache (bypassing DRAM entirely).
As such, I/O performance portability between x86 servers (in particular: Intel Xeon vs AMD EPYC) suffers from similar I/O issues. Even if you have AMD EPYC + Intel Ethernet, you lose the direct-to-L3 DMA, and will have slightly weaker performance characteristics compared to Intel Xeon + Intel Ethernet.
Or Intel Xeon + Optane optimizations, which also do not exist on AMD EPYC + Optane. So these I/O performance differences between platforms are already on the status-quo, and should be expected if you're migrating between platforms. A degree of testing and tuning is always needed when changing platforms.
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>Still, are there many public clouds built of these Ampere Altra-s? Maybe we gonna have them widespread soon, but until then I wouldn’t want to build stuff that only runs on Amazon or my own servers with only a few on the market and not yet globally available on retail.
A fair point. Still, since Neoverse N1 is a premade core available to purchase from ARM, many different companies have the ability to buy it for themselves.
Current rumors look like Microsoft/Oracle are just planning to use Ampere Altra. But like all other standard ARM cores, any company can buy the N1 design and make their own chip.