The IBM System/370 Model 155 (and the Model 165)[2] were jointly announced Jun 30, 1970[3] as "designed for ... the Seventies." That same day IBM announced the 370/195.[NB 1] They were the first three models of the IBM System/370 line of computers.
 | |
.jpg) IBM System/370 Model 155 | |
| Manufacturer | International Business Machines Corporation (IBM) |
|---|---|
| Product family | System/370 |
| Release date | June 30, 1970 |
| Discontinued | December 23, 1977 |
| Website | Official website IBM Archives |
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the 370/155 (and 165)
came the Model 145.[1]
Unlike the 155 (or 165),
the 145's lack of virtual memory could be rectified with a simple microcode update from a floppy disk, vs the others needing a hardware upgrade.
Direct Access Storage Facility,
code-named Merlin, was introduced in June 1970 for use with the IBM System/370. Its removable disk packs could hold 100 MB
Three months later a fourth IBM System/370, the Model 145, was announced. Since none of them came with virtual memory, "which was to be a hallmark of the 370 line"[4] some said about these early members of the IBM System/370 family, especially about the 165 and 155, that they were not "the real 370 line."[NB 2]
Limitations edit
Some said about these early members of the IBM System/370 family, looking back, that they were not "the real 370 line" because "neither offered virtual storage capability, which was to be a hallmark of the 370 line."[4]
The 370/155 was described as able to "run under DOS." Both the 155 and the larger 370/165 could "run under OS/360." Being members of the System/370 family, the Model 155 and Model 165 were compatible with each other. Neither machine, as announced, could run a virtual memory operating system.
Growth path edit
The initially announced systems were in many ways merely improved IBM 360 systems. Both were announced as running 360 Operating Systems.[NB 3] No mention was made of virtual memory or new operating systems.
The IBM System/370's basic architecture was described as having been "extended, but not redesigned" from that of IBM System/360.[2]
Upgrade option edit
In 1972 an upgrade option was announced "to provide the hardware necessary to operate in a virtual memory mode."[5]
Unlike the IBM System/370 Model 145, which as early as June 1971 could have virtual memory capability added to it with a simple microcode update from a floppy disk, the Model 155 and Model 165 needed expensive hardware additions—$200,000 for the 155 and $400,000 for the 165—to add virtual memory capability, and even this had to wait until 1972, at which time their upgraded 155 was known as an IBM System/370 Model 155-II.[6]
Physical memory edit
Although the joint 155/165 announcement[2] did not have the word virtual, there were multiple references to (physical) memory, storage (both main memory and disk storage), and cache memory under the name "buffer".
The 155 had seven main memory choices, ranging from 256 KB to 2 MB; the 165: five possibilities, from 512 KB to 3 MB. Both models were described as having "a very high-performance buffer storage backed by a large" main memory.
Another signs of not being "the real 370 line" is that the main storage in 3155 was not monolithic, it was using the older type of ferrite core storage. The 3360 storage unit could have 256 or 512 KB of storage, each 3155 could have one to four 3360 units attached. Also, the microcode in 3155 was "hardwired" while later 370 systems loaded the microcode from a floppy disk, enabling easy upgrades. The 3155 also had very limited error logging capability and used an IBM 3215 typewriter console.
Channels edit
Channel 0 was a byte multiplexor channel, channel 1 to 5 were block multiplexor channels. Channel 0 and 1 were standard, channel 2 to 5 were optional upgrades.
See also edit
Notes edit
- ^ coming about 14 months after the announcement of the 360/195. Both 195 machines were withdrawn Feb. 9, 1977. see https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2195.html and https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3195.html
- ^ The 195 was noted as "at the time of its introduction, ... IBM's most powerful computing system" and the 145's microcode could be upgraded from a floppy disk. By contrast, the 155 and 165 needed a hardware addition priced at $200,000 and $400,000 respectively
- ^ DOS on the 155, MFT or MVT on either machine
References edit
- ^ "System/370 Model 145". IBM Archives. IBM. 23 January 2003.
- ^ a b c "System/370 Model 165". IBM Archives. IBM. 23 January 2003.
- ^ "System/370 Model 155". IBM Archives. IBM. 23 January 2003.
- ^ a b "What Course for the 3081?". Computerworld. November 24, 1980. p. 34.
- ^ "First IBM DAT Box Installed". Computerworld. August 15, 1973. p. 17.
- ^ A. Padegs (September 1981). "System/360 and Beyond". IBM Journal of Research & Development. 25 (5). IBM: 377–390. doi:10.1147/rd.255.0377. – tables include model characteristics (Table 1) and announcement/shipment dates (Table 2). The S/370-155-II and -165-II are listed under the former but not the latter, because the upgraded systems were not formally announced as separate models. The "System/370 Advanced Function" announcement, including the -158 and -168, was the main public event.