Amdahl is making field modifications to some of its mainframes, after users complained they weren't delivering the promised performance.
The Fujitsu owned company announced this week that affected models of its GS800 S/390 mainframes are to be rebadged as GS2000 machines - a brand not due to be launched until the final quarter of this year. The capacity of the machines is to be restated as 914 Mips, instead of 1,075 Mips.
Last week Amdahl admitted some GS800 machines were failing to deliver the promised performance under core workloads. It said then that the performance gap was in single digits.
Because mainframe software licence fees are generally charged on the basis of machine capacity, this left some users overpaying for their software.
Affected users will have their machines reconfigured as GS2000A machines at no additional cost, said Carol Stone, director of server marketing for Amdahl.
However, she added that Amdahl has no plans to reimburse customers who have been overcharged for their software.
Stone said the models would feature improvements both in the hardware and software, including a feature allowing users to increase capacity by incremental steps.
Instead of having to upgrade by a full processor, users can add on an additional processor with a lower performance rating, meaning they don't have to pay the full upgrade cost on their software licensing.
Barry Graham, independent analyst for Xephon, said Amdahl was taking positive action to fix the problems.
"As I understand it they've made significant changes in the microcode for the new models," he said.
GS2000C models will have a capacity of up to 1600 Mips, and the GS2000E, shipping early next year, will have a capacity of up to 2,000 Mips.
For more stories see this week's issue of Computing
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