The offers, made on IBM's low-end model 270-2433 and high-end model 820-2436 iSeries Servers, would cut the cost of the machines from $47,000 (£30,101) to $23,000 (£14,731) and $110,000 (£70,750) to $55,000 (£35,225) respectively. The iSeries machines replaced the AS/400 line in October 2000.
David Bruce, IBM's worldwide iSeries product marketing manager, said the programme would let users upgrade their machines to gain better performance with their existing Unix applications.
The machines run IBM's OS/400 operating system on Power III processors. They also provide dynamic logical partitioning, allowing users to run native iSeries applications, Linux, Windows 2000, Windows NT and Unix applications simultaneously in their own partitions.
IBM has also offered discounts of up to 38% on additional software or software subscription packages, Bruce said.
The programme, which is being called "Green Streak" inside IBM because of the push to replace old green-screen AS/400 systems, covers purchases installed by 31 December.
IBM has conducted similar upgrade programmes in the past, Bruce said, but this is the largest effort to date for the iSeries line. IBM has sold about 750,000 AS/400 and iSeries machines. About 475,000 are still in use by about 210,000 active customers, he said.
Brad Day, an analyst at Giga Information Group, said the programme could help IBM minimise its support costs for older, out-of-production AS/400 machines if it can get users to migrate to the newest servers. Day said the new servers would benefits users who wanted to reduce their IT infrastructure and costs.
Charles King, an analyst at Sageza Group said: "It's a good way for IBM to perk up interest", while offering existing AS/400 customers an economical way to stay with the proprietary platform over cheaper Intel and Windows-based machines.