When ICL Ltd launched its two latest SX (Essex) mainframes - the SX 580-20 and the 550-20 - back in May (CI No 1,419), the company denied that this was an attack on IBM's Summit machines, claiming rather that the latest members of ICL's VME-based Series 39 systems had been introduced simply to provide increased levels of per-formance for users of the existing family of the ICL VME operating system. And, compared with its predecessor - the Series 39 Level 80 machine - SX uses three times as much logic, has a clock beat of less than half, and has increased the performance by a factor of four. The Series 39 range of machines, announced in 1985, and initially comprising two processor designs code-named Estriel and DM1, was developed as a compatible evolution from the previous 2900 series, with improved multi-processors made by incorporating nodal architecture where nodes are interconnected via Macrolan fibre optic cable networks.
Got there first
This proprietary ICL serial connection system - developed in conjunction with STC Plc - enables processing nodes and the input-output controllers within a system to operate with separations of over one mile, which facilitates remote operation and dispersed systems for disaster proofing and so on. Besides the high speed that can be achieved, and the disaster proofing, says ICL, another advantage of using fibre optics is that there is no electromagnetic radiation to be picked up - an important issue for security. And it is cheaper to install. In September, IBM introduced the ES/9000 with Escon fibre optic connections but until then ICL had produced the only mainframes with fibre optic technology. Andy Irvine, marketing manager for SX systems, says he likes to think that ICL got there first because of its investment in research and development, added to the fibre optics technology brought in by STC Telecommunications. As the next compatible evolution in the Series 39 range, the SX system features higher bandwidth fibre optic technology - the SX uses the 200Mbits-per-second Macrolan variant as opposed to the 50Mbps used by the previous Series 39 machines - and has been made to multi-node and input-output connections. The input-output system on SX provides up to 16 Macrolan channels, which are used for peripheral access to both fast and slow devices. The input-output hardware is made up of a single Macrolan channel concentrator and up to 16 Macrolan daughter boards. High speed input-output is driven using the same VME interface as was used on previous Series 39 machines, which has removed the need to change VME for all disk and tape driving. For low speed devices, the Oslan (Ethernet) protocol is handled over the Macrolan and a new sub-system has been introduced to VME - Remote Coupler Handling - to support this. This packages up the Oslan data and passes it over the Macrolan-to-Oslan Gateway, which then drives the Oslan. In this arrangement, there are no slow connections directly to the node. -
By Susan Norris
The SX node consists of four units - the order code processor, the input-output processor, the inter-node processor and the store, with much of the functionality of the inter-node and input-output processors being provided by the heavily pipelined order code processor. At the highest level, this consists of four asynchronous units: the scheduler, the upper pipe, the data slave and the lower pipe - the last three units considered as a single unit - the engine. The scheduler fetches 2900 order code and decodes it to give a sequence of Picode which the engine then obeys. Picode is the implementation order code of the SX order code processor - it takes the place of microcode on previous machines but is at a higher level, much closer to the 2900 order code. Picode is executed by the engine. Basically, SX is seeing a return to the old way of hardwiring target level code into the machine, obviating the need to convert microcode into different instructions - the previous Series 39 machines weren't hardwired and, although more adaptable, were slower. The motivation for this step ba
ckwards came from an analysis of the Series 39 L80 - in particular its processor - whereby trace data relating to instruction sequences and data addresses were gathered, and performance, for example in teleprocessing, was monitored using different workloads. With the power of the individual nodes in an SX multi-node system, a high-performance inter-node service - capable of supporting a multi-node system with up to eight nodes - has been developed to cope with the increase in the amount of multi-node traffic. This uses four optical cables as data links, and one for chronology. For resilience and system partitioning purposes there is a second Token Ring. Store images can be replicated on different nodes and to maintain a coherent store image across these nodes, a chronology is applied to all writes to this store by means of a Token Ring Serial Number which is carried by the single token on the token serial ring. At the heart of the SX CPU is the Sub-System Carrier which comprises a 21.3 by 19.2 42-layer printed circuit board on which are mounted up to 336 of Fujitsu's Hawk Emitter Coupled Logic arrays which are made to ICL's design. Extending Fujitsu's Single Board CPU concept, the input-output and memory control system logic are incorporated on this same board.
This reduces transfer time delays on the associated interfaces. SX logic chips are 1.6 times faster than those in Estriel and have much higher density - 3,000 gates versus 400 gates. With more gates per chip, the SX requires fewer chips, thus improving reliability. The main store unit offers up to 512Mb capacity per node in units of 128Mb, and over 100 FDS disk drives can be attached, enabling access to up to 6Tb of storage. ICL measures the success of its new development by comparing it with Amdahl's two-year-old 5990 mainframe - which, like the new SX machines, is built using Fujitsu's Hawk Emitter Coupled Logic gate-arrays. Says T A Hinchcliffe, director of ICL Computer Products, the SX 580-20 is less than a sixth of the weight of the 5990-1100, uses less than a quarter of the floor space, takes up less than half the power, and puts out less than half the heat - while giving 50% more power per processing node. The SX 580-20 and the SX 550-20 are dual processors, and ICL is planning to go up to six processors, with uniprocessor models scheduled for next year. ICL rates a two-node SX 580-20 at 90 IBM MIPS - the six-node configuration is expected to reach 300 MIPS, and the low-end two-node 550-20 rated at 60 IBM MIPS. Customers of the SX systems so far include Racal Vodafone (CI No 1,491), the Inland Revenue which now has two of the new mainframes, and Yorkshire Electricity and West Midlands Gas. And Walsall Metropolitan Borough Council has ordered a two-node SX 550-20 system, which is scheduled for delivery next year and will replace a two-node Series 39 Level 80, under ICL's exchange-hire scheme.
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