Top Document: PDP-8 Summary of Models and Options (posted every other month) Previous Document: What is a DECmate I? Next Document: What is a DECmate III? See reader questions & answers on this topic! - Help others by sharing your knowledge Date of introduction: 1982 Date of withdrawal: 1986 Also known as: PC27X series. Price: $1,435 Technology: Based on the 6120 microprocessor, this shared the same packaging as DEC's other competitors in the PC market, the Rainbow (8088 based) and the PRO-325 (PDP-11 based). Reason for introduction: This machine was introduced in order to allow more flexibility than the DECmate I and to allow more sharing of parts with the VT220 and DEC's other personal computers. Compatability: Same as the DECmate I, except it could continue from a halt. There was better hardware for device emulation support, allowing for somewhat better real-time performance. The data communications port was an incompatable improvement on the incompatable DECmate I communications port. No built-in terminal emulation was provided, and the data communications port supported only one line, but aside from this, the data communications port is essentially as powerful as the DP-278B on the DECmate I. Standard Configuration: The DECmate II was sold with 32K of program memory, plus a second full bank for dedicated control panel function emulation. Code running in the second bank is sometimes referred to as slushware; it looks like hardware to the PDP-8 user, but it is actually device emulation software that is loaded from the boot diskette. An integral RX50 dual 5 1/4 inch diskette drive with an 8051 controller chip was included, along with a printer port, a 100Hz real-time clock, single data communications port, and interfaces to the monitor and keyboard. The diskette drive can read single-sided 48 track-per-inch diskettes, so it might be possible to read (but not write) IBM PC diskettes on it. Expandability: This was the most open of the DECmate systems, with a number of disk options: An additional pair of RX50 drives could be added, and with the RX78 board, it could support a pair of dual 8 inch drives, either RX01 or RX02. As an alternative to the RX78, there was a controller for an MFM hard drive. The interface to the RX78 board wasn't fully compatable with earlier interfaces to RX01 and RX02, and there was no way to have both an RX78 and an MFM drive. The MFM drive could be up to 64 MB, with 16 sectors per track, 512 bytes each and at most 8 heads and 1024 (or possibly 4096) cylinders. A power supply upgrade was needed to support the MFM drive. DEC sold this machine with 5, 10 and 20 meg hard drives, Seagate ST-506, 412, and 225 respectively. A graphics board supporting a color monitor could be added in addition to the monochrome console display; two variants of this board were produced during the production run, all slightly incompatable. A coprocessor board could be added, with communication to and from the coprocessor through device 14. DEC sold three boards, an APU board (Z80 and 64K), and two XPU boards (Z80, 8086 and either 256K or 512K). If these added processors are used, the 6120 processor is usually used as an I/O server for whatever ran on the coprocessor. The XPU boards used a Z80 for I/O support, so 8086 I/O was very indirect, particularly if it involved I/O to a PDP-8 device that was emulated from control memory. Despite this, the DECmate version of MS/DOS is generally faster than MS/DOS on more recent 80286 and 80386 based IBM PCs because of effective use of the coprocessors (but they couldn't run MS/DOS code that bypasses MS/DOS for I/O). Survival: As with the DECmate I. User Contributions:Top Document: PDP-8 Summary of Models and Options (posted every other month) Previous Document: What is a DECmate I? Next Document: What is a DECmate III? 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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