2018年3月7日 · The PDP-8/S, which arrived shortly after the original PDP-8, was in this category; however, because it used a serial arithmetic unit, it was slow and of limited popularity. The PDP-8/L, a computer using the same technology as the PDP-8/I, but with fewer available options, also had its logic behind the front panel.

2014年5月31日 · PDP-8 programs that emit predefined messages almost always use the upper-case only 64 char TTY set, and store them as two 6-bit chars per word. The DEC PDP-8 assembler (PAL) (except the earliest editions) includes directives to pack literal strings.

2018年3月2日 · The PDP-8 designers wanted memory reference instructions (MRI) like TAD to be able to address zero-page, indirect, current-page, and zero-page-indirect memory references, which requires 2 bits in the instruction word: 00, 10, 01, and 11, respectively. That leaves 7 bits for MRI instructions, which gives the PDP-8 page size of 2⁷ = 128 words.

2024年1月12日 · This answer is written from information sourced from PDP-8/E & PDP-8/M & PDP-8/F Maintenance Volume 1 (PDF warning). Here is a description of the datapath allowing the program counter to be incremented on the PDP-8/E, this is figure 3-2 in the book):

2025年2月2日 · All the PDP-8 I know have magnetic core, and you can see in the OS/8 manual that the manual authors also made the assumption "it's magnetic core, and keeps the value". If you have any information about existing installations with semiconductor memory, then the next question would be what other periphery they were using, and if they were using ...

2016年10月20日 · The static load is an irreducable 5 instructions per additional word of precision. The dynamic load is 8 to 11 cycles per word of precision, depending on indirection. The PDP-8 programmers I worked with at DEC felt this arrangement of operations was the most easily proved correct. Some DECUS contributors may have had other opinions.

2024年1月10日 · I'm trying to find a single clear statement of the limits to the numbers represented in the PDP-8's three-word format. I found the original documents on this, but they are, ahem, not exactly forthright with this information. Page 3.10 shows the format with the exponent in the first word and the mantissa in the next two, but the exact format of ...

2024年2月4日 · Furthermore, the PDP-8 and PDP-11 are very different architectures, and their assembler is quite different. An example of a machine which is similar to the PDP-8 is the HP-2100, even though it is 16 bits, the instructions are much more similar and the architecture is more similar to the PDP-8.

2024年1月12日 · The PDP-8 was a remarkable exercise in minimalist computer design; some of the aspects of its design are discussed in detail at PDP-8 transistor count One feature it did not have was a stack. Instead, ...

2023年4月5日 · While the PDP-8 indeed frequently used 6-bit characters packed into a word, the way FOCAL handled "alphanumeric numbers" seemes to be different. You can easily run a PDP8 FOCAL in simh, and you can use the TYPE command with exponential formatting to see what happens on conversion: