The successor IBM Mainframes are still alive... for the time being.
replies(2):
they also moved on three more CPU generations since that redbook, to z17.
I think it's Linux on Z that makes it sexy and keeps it young, in addition to a number of crazy features, like a hypervisor that can share CPUs between tenants, and a hardware that support live migration of running processes between sites (via fibre optic interconnect) and the option to hot swap any parts on a running machine.
It's doing a number of things in hardware and hypervisor that need lots of brain power to emulate on commodity hardware.
_and_ it's designed for throughput, from grounds up.
Depending on your workload there may be very good economical reasons to consider a mainframe instead of a number of rack-frames.
For legacy companies yes but it would be very hard for new YC companies or existing non-mainframe companies to create a spreadsheet showing how buying a new IBM Z mainframe would cost less than the latest commodity x86 or ARM servers in the cloud or on-premise.
The IBM pricing for mainframes makes sense for legacy companies like banks and airlines with a million lines of old COBOL code that want to keep it all running with the latest chip technology. (The mainframes from a few years ago are coming off the lease and they need to upgrade to whatever new mainframe IBM is offering and sign another lease & service contract.) So, IBM mainframe prices are very expensive -- but legacy companies will pay it because migrating the code away from mainframes can be even more expensive.
It's similar to expensive enterprise pricing of Oracle, Embarcadero Delphi, Broadcom etc that takes advantage of existing customers already locked into their products. Virtually no new tech startup with a greenfield project is going to pay Delphi $1599-per-seat for each of their developers. Only existing customers stuck with their investment in Delphi code are going to pay that. (https://www.embarcadero.com/app-development-tools-store/delp...)
But some companies do endure the costs of migration to get out from IBM lock-in. There are lots of case studies of companies shifting their workload from mainframes to AWS/GCP/Azure. I can't think of a notable company that did the reverse. Even a mainframe hardware vendor like Fujitsu quit making mainframes and shifted to x86 running an emulation of their mainframe os.
Yes, IBM mainframe can run other workloads besides COBOL like Java and C/C++ but no company that's not already using mainframes would buy & deploy to IBM's Z hardware for that purpose.
mainframe pricing usually is not by pound of iron but per cpu cycle. unless you say nah I'm buying the thing, not just cycles. soyou have a choice of cloud pricing or hardware pricing.
for significant pure Linux workloads that need an own on premise cloud the TCO pricing is surprisingly competitive with any home grown solution.
even if you don't _need_ an own on premise cloud, AWS and similar donate come for free and there may be a break even there, too.
that said, legacy host software, Delphi, cics, Oracle, DB/2, cobol etc, you named it, yes that's a different story, with all the extra software licensing.
but a pure Linux mainframe is surprisingly competitive not just in compute and throughput but also in pricing.
plus you get quite some high availability in silicon. think ECC on the ALU, hot stand by spare CPU, multipath everything, if your business depends on uptime your system architecture becomes much simpler on highly dependable hardware.
so that spreadsheet compares own people and software construction vs IBM tax in some columns.
lol I start sounding like an IBM sales person https://www.ibm.com/products/integrated-facility-for-linux
I just did Linux on Z for a while and I loved it, so please bear my enthusiasm :-D
It's not competitive when you consider what long-time IBM mainframe customers actually do. E.g. SABRE airline and travel reservation system was one of the first IBM mainframe customers in 1960 with the IBM 7090 and then upgraded to System 360 and then the newer Z mainframes. SABRE's multi-decade experience with IBM mainframes with mission-critical business applications means they are one of the world's foremost experts on its capabilities & costs that's not biased by any IBM marketing or sales pitches.
Even with all that in-house experience, SABRE still chose to gradually migrate off of IBM mainframes to less expensive tech stacks. Some have touted IBM's TPF (Transaction Processing Facility) on the mainframe as compelling technology but that still didn't dissuade SABRE in ~2001 when they migrated the airfare pricing application to Tandem (Compaq/HP) NonStop servers running UNIX. (https://www.computerworld.com/article/1339621/has-mainframe-...)
They then started a 10+ year effort to migrate more mainframe workloads to Google Cloud. E.g. from https://www.sabre.com/insights/a-journey-to-tackle-legacy-co... :
> We moved 93% of compute capacity from physical data centers to the public cloud, resulting in a 50% decrease in our compute costs.
> We migrated more than 120 million bookings from a mainframe-based system to one using Google Cloud’s Spanner database, without impacting customer operations.
JP Morgan Bank is another example of migrating from IBM mainframes to cloud. If anyone out there truly thinks that running a new greenfield Linux workload will be be cheaper or even cost-competitive on a new IBM Z mainframe, just pause and consider if you truly know something about IBM mainframes' OpEx that multi-decade IBM customers like SABRE and JP Morgan don't already know.
Why would any new customers in 2025 willingly buy into IBM Z mainframes if they see existing customers spending billions trying trying to move off of them?
Nearly every installation site and their internal support director agrees that the z/OS installations are far less expensive to support, simply because the minimum level of experience for a z/OS engineer is about a magnitude more than a cloud engineer.