Top Document: PDP-8 Summary of Models and Options (posted every other month) Previous Document: What is a LINC-8? Next Document: What is a PDP-8/I? See reader questions & answers on this topic! - Help others by sharing your knowledge Date of introduction: 1966 (Unveiled, Aug 23, WESCON, Los Angeles). Date of withdrawal: 1970. Total production run: 1024, or over 1500 The first figure is from Computers and Automation, based on figures released by the manufacturer. The second figure is based on memory of the first-year production run. We need to look at the serial numbers on surviving machines to pin this down! Price: $10,000 Technology: DEC Flip Chip modules and core memory, as in the PDP-8. Unlike the PDP-8, the PDP-8/S memory module was mounted between a pair of quad-height single-width boards that plugged into the standard flip-chip sockets (this was sold separately as the H201 core memory unit, at $2000 for 4K by 13 bits). It is noteworthy that the prototype machine was built using Digital Logic Laboratory H901 plugboards and patchcords, based entirely on off-the-shelf modules. Another new feature of the PDP-8 was its use of a single internal bus within the machine for all register transfers. This was, of course, bit serial, but the idea formed the basis for the DEC UNIBUS and OMNIBUS and essentially all later bus-oriented CPU designs. Reason for introduction: This machine was developed as a successful exercise in minimizing the cost of the machine, in response to a complaint by Ken Olson that the company hadn't gotten the price of the PDP-8 down any further, and the vision that someday, people ought to be able to buy a desktop PDP-8 for under $10,000. The result was the least expensive general purpose computer ever made with second generation (discrete transistor) technology, and it was one of the smallest such machines to be mass produced (a number of smaller machines were made for aerospace applications). It was also incredibly slow, with a 36 microsecond add time, and some instructions taking as much as 78 microseconds, even though the internal clock ran faster than that of the original PDP-8! By 1967, DEC took the then unusual step of offering this machine for off the shelf delivery, with one machine stocked in each field office available for retail sale. Reason for withdrawal: The PDP-8/L vastly outperformed the PDP-8/S, and and it did so at a lower price. Compatability: The core of the PDP-8 instruction set is present, but there are a sufficient number of incompatabilities that, as with the PDP-5, many otherwise portable "family of 8" programs will not run on the PDP-8/S. Perhaps the worst incompatability is that the Group 1 OPR instruction CMA cannot be combined with any of the rotate instructions; as with the PDP-8, IAC also cannot be combined with rotate. Standard configuration: CPU with 4K of memory, plus PT08 110 baud current loop teletype interface and teletype. Both a rack-mount and table-top versions were sold (both 9" high by 19" wide by 20"? deep). The rack mount version included slides so it could be pulled out for maintenance. Expandability: The CPU supported the standard PDP-8 negibus, but I/O bandwidth was 1/5 that of the PDP-8. Thus, most, but not all PDP-8 peripherals could be used. A few DEC peripherals such as the DF32 came with special options such as interleaving to slow them down for compatability with the PDP-8/S. The speed problems were such that there was never any way to attach DECtape to this machine. Survival: Because they were so slow, PDP-8/S systems were quickly discarded as newer machines became available for comparable prices; thus, they are less common today than the Classic PDP-8, even though comparable numbers were made. A few survive in working condition. User Contributions:Top Document: PDP-8 Summary of Models and Options (posted every other month) Previous Document: What is a LINC-8? Next Document: What is a PDP-8/I? Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jones@cs.uiowa.edu (Douglas W. Jones)
Last Update March 27 2014 @ 02:11 PM
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