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If IBM mainframes had amazing MIPS/$ IBM would make sure the world knows it.

rbanffy 2y ago
CPU MIPS is just a small part of the equation here. A mainframe has lots of specialized hardware dealing with IO that allow the CPU to be running application code close to 100% of the time. A pure CPU intensive benchmark would be misleading and the restriction on publishing benchmarks is not really aimed towards the users, but towards the competition - who'd be more than happy to compare machines with different designs and different performance characteristics to IBM's designs. MIPS per MIPS, IBM itself offers solutions that have higher processing power than mainframes in their POWER and IBMi series of machines. And you can surely assemble an x86 or ARM monster with a lot of cores, but it won't match the performance of the Z for the workloads it is designed for - on-line transaction processing.
- UltraSane 2y ago
  I'm sure the absolute performance of the Telus II CPU is very good since it runs at 5.5Ghz and has 36MB of L2 cache per core. But I'm talking about price per dollar and this is where IBM mainframes fail miserably because IBM charges through the nose for them. I would not be surprised if a IBM mainframe costs 10x of what a x86 or ARM server of equal performance does.
  - rbanffy 2y ago
    Performance is not a single number. Mainframes are terrible choices for HPC, AI training, data analytics, etc. Where they excel is that narrow niche of high-volume, real-time transaction processing. In order to get there, the whole design of the machine is carefully balanced - the right number of cores per socket, the cache sizes (and the dynamic allocation of L3 and L4 according to pressures, trying to minimize eviction) all the way to CICS, z/OS and the way they allocate memory and processing power.
    - UltraSane 2y ago
      The main selling points of z/OS and hardware is the amazing uptime and 60 years of backwards compatibility. There isn't a single computational workload that a IBM mainframe can do cheaper than a x86 server/cluster.

CPU MIPS is just a small part of the equation here. A mainframe has lots of specialized hardware dealing with IO that allow the CPU to be running application code close to 100% of the time. A pure CPU intensive benchmark would be misleading and the restriction on publishing benchmarks is not really aimed towards the users, but towards the competition - who'd be more than happy to compare machines with different designs and different performance characteristics to IBM's designs. MIPS per MIPS, IBM itself offers solutions that have higher processing power than mainframes in their POWER and IBMi series of machines. And you can surely assemble an x86 or ARM monster with a lot of cores, but it won't match the performance of the Z for the workloads it is designed for - on-line transaction processing.

UltraSane 2y ago
I'm sure the absolute performance of the Telus II CPU is very good since it runs at 5.5Ghz and has 36MB of L2 cache per core. But I'm talking about price per dollar and this is where IBM mainframes fail miserably because IBM charges through the nose for them. I would not be surprised if a IBM mainframe costs 10x of what a x86 or ARM server of equal performance does.
- rbanffy 2y ago
  Performance is not a single number. Mainframes are terrible choices for HPC, AI training, data analytics, etc. Where they excel is that narrow niche of high-volume, real-time transaction processing. In order to get there, the whole design of the machine is carefully balanced - the right number of cores per socket, the cache sizes (and the dynamic allocation of L3 and L4 according to pressures, trying to minimize eviction) all the way to CICS, z/OS and the way they allocate memory and processing power.
  - UltraSane 2y ago
    The main selling points of z/OS and hardware is the amazing uptime and 60 years of backwards compatibility. There isn't a single computational workload that a IBM mainframe can do cheaper than a x86 server/cluster.