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"Today’s System z, itself an evolution of the original System/360 and 370, can still run many of the original programs, unmodified, from 50 years ago. This is

"Today’s System z, itself an evolution of the original System/360 and 370, can still run many of the original programs, unmodified, from 50 years ago. This is a testament to 2 things, the wide adoption of the IBM systems, and the forward thinking of IBM." Or rather the crazy levels backwards compatibility and effort to build what is basically a hardware emulator for a 50 year old machine. Put another way, IBM isn't making native ficon disks, they build a fancy controller that uses SAS/etc disks and presents them as ficon, which runs on the same physical transport as fiber channel, rather replacing much of the protocol stack. The resulting MOD3 or MOD9/etc disks appear like 3390 model 9 disks circa the late 80's early 90's. AKA instead of a room sized disk they are basically virtual with all the overhead that implies. The CPU's are of course native, but like all the other ISA's reflect a more modern design style of basically cracking the CISC instructions into an out of order superscalar CPU and only using "micro code" for the really complex instructions.

Shivetya 10y ago
while the iSeries (think AS/400) has a shorter history many programs compiled to earlier versions run on later versions due to the separation of hardware layer from operating system layer. The system can recompile existing programs without human usable/retrievable source due to the method use to encode them. there is code from the eighties running in slightly updated form on our z and even the i series systems have twenty year old code. both systems have web facing extensions that directly map to older code (as in, green screen 3270/5250 that has no change to its code) pretty much seamlessly. new code is often employed as necessary but the idea that stuff that worked well that is a decade or more old still works today is what amazes me about the various IBM platforms
- bluedino 10y ago
  So much of our iSeries code has (c) 1979 in the header. Nearly 40 years.
bogomipz 10y ago
>""Today’s System z, itself an evolution of the original System/360 and 370, can still run many of the original programs, unmodified, from 50 years ago" Wasn't this the value proposition of System 360, that IBM guaranteed that software for it would be supported in perpetuity basically? This is why there are still so many IBM main frames around in government running COBOL. Here's an interesting top 10 list of the oldest system in the US Federal government. Look how many of them are IBM Mainframe/COBOL: http://www.nextgov.com/cio-briefing/2016/05/10-oldest-it-systems-federal-government/128599/ http://www.nextgov.com/cio-briefing/2016/05/10-oldest-it-sys...

Shivetya 10y ago

while the iSeries (think AS/400) has a shorter history many programs compiled to earlier versions run on later versions due to the separation of hardware layer from operating system layer. The system can recompile existing programs without human usable/retrievable source due to the method use to encode them. there is code from the eighties running in slightly updated form on our z and even the i series systems have twenty year old code. both systems have web facing extensions that directly map to older code (as in, green screen 3270/5250 that has no change to its code) pretty much seamlessly. new code is often employed as necessary but the idea that stuff that worked well that is a decade or more old still works today is what amazes me about the various IBM platforms

bluedino 10y ago
So much of our iSeries code has (c) 1979 in the header. Nearly 40 years.

bogomipz 10y ago

>""Today’s System z, itself an evolution of the original System/360 and 370, can still run many of the original programs, unmodified, from 50 years ago" Wasn't this the value proposition of System 360, that IBM guaranteed that software for it would be supported in perpetuity basically? This is why there are still so many IBM main frames around in government running COBOL. Here's an interesting top 10 list of the oldest system in the US Federal government. Look how many of them are IBM Mainframe/COBOL: http://www.nextgov.com/cio-briefing/2016/05/10-oldest-it-systems-federal-government/128599/ http://www.nextgov.com/cio-briefing/2016/05/10-oldest-it-sys...