kens

61 ms·

931.
by kens 4y ago
No, that's off by three orders of magnitude. 10 kbar is 145,000 psi. (Google gives you the wrong answer because it treats "10 bar in psi" and "10 kbar in psi" identically which is bad.)
932.
by kens 4y ago
My source is "The Architecture of Microprocessors", which has a very detailed chapter on the internals of the 68000. Each micro-instruction consists of a 17-bit sequencing field and a 68-bit action field (85 bits in total). These
933.
by kens 4y ago
There's more pipelining in the 8086 than you might expect, with a micro-instruction pipelined across three clock cycles. I explain this in more detail here: https://www.righto.com/2023/01/the-8086-processors-m
934.
by kens 4y ago
As Vonada said†, "Digital circuits are made from analog parts." On the one hand, you can simulate just about everything in the 8086 as digital.†† On the other hand, the transistors in the 8086 (and other processors) are carefully
935.
by kens 4y ago
I think it was the book "102 Minutes: The Untold Story of the Fight to Survive Inside the Twin Towers". I'm not 100% sure since I read the book many years ago.
936.
by kens 4y ago
The ceiling hatch of an elevator is normally locked from the outside. You may be able to pry the doors open. However, in this case, the elevator was an express elevator and the door opened onto a cinder block wall. In the 1993 World Trade C
937.
by kens 4y ago
For more, see this long New Yorker article that includes a lot of elevator history: https://www.newyorker.com/magazine/2008/04/21/up-and-then-do... The quick summary is that Mr. White recovered from the
938.
by kens 4y ago
This article is somewhat pointless. It cites two studies, one which found correlations between ultra-processed food and cognitive decline, and one which found that it does not. It concludes that more research is needed.
939.
by kens 4y ago
At least on the early Soviet space missions, the cosmonauts had almost no control by default and most of the control was by onboard sequencing. The controls were actually locked with a combination lock. The Globus was more of a backup. The
940.
by kens 4y ago
Thanks! I primarily post on Twitter as @kenshirriff but also post on Mastodon.
941.
by kens 4y ago
An interesting thing about these transistors is they look like standard power transistors in a metal TO-3 package. However, the transistor itself is in a round metal package, and the metal flange is separate, and holds down the transistor.
942.
by kens 4y ago
The clever thing about the globe is that it doesn't do arbitrary rotations, so the mechanical connections are simplified. Instead, it has two degrees of freedom through two fixed, co-axial shafts. Specifically, the globe rotates at an
943.
by kens 4y ago
I think the Soyuz-TMA spacecraft (2002) upgraded to the Neptun-ME system, which has digital displays rather than the Globus.
944.
by kens 4y ago
I agree with you 100% there. The Datapoint 2200 (which the 8008 cloned) used octal for its instructions and the instruction decoding is almost trivial to understand. Unfortunately, Intel used hexadecimal for the documentation. In hex, you c
945.
by kens 4y ago
A change from my 8086 posts. Any questions about the Globus?
946.
by kens 4y ago
What pushed computing toward eight bit bytes is the IBM System/360 (1964) which dominated the computing industry at the time. It used 8-bit EBCDIC (with ASCII as an afterthought). If ASCII didn't exist, we'd still be using by
947.
by kens 4y ago
One problem with this theory that ASCII killed off octal is that ASCII was introduced in 1963, while octal was popular into the mid-1970s. The real reason that hex beat octal is 16-bit words. It's trivial to break a 16-bit word into tw
948.
by kens 4y ago
I haven't studied the 8088 super-closely. There are a moderate number of changes. For instance, the prefetch registers in the 8088 needs to be updated a byte at a time, so they need separate write control lines for the low and high byt
949.
by kens 4y ago
A bit surprisingly, I don't miss it at all. (Except for the Google meals.) I'm enjoying working on a bunch of projects.
950.
by kens 4y ago
I haven't tried glitching an 8086, but I have chatted with Steve Morse, creator of the 8086 architecture.
951.
by kens 4y ago
The instruction bytes were in a queue, not a stack, so it's not really like Forth. It's the same as reading the bytes in order from memory except the queue improved performance by reading instructions when the bus was otherwise fr
952.
by kens 4y ago
It's kind of amazing how many hard computer problems from the olden days were solved by having more memory. When I got started in computer graphics, there was a lot of research work on how to render images a scanline at a time, since t
953.
by kens 4y ago
Reset happens immediately, so at least that would let you escape.
954.
by kens 4y ago
No, I don't get paid for this. The time-management secret is to retire :-)
955.
by kens 4y ago
I haven't tested a physical chip to verify, but based on my simulations I think you are correct. For your second example, a side effect is that NMI is blocked until the end of the instruction, so you could block the NMI interrupt for a
956.
by kens 4y ago
Yes, more 8086 microcode. I'm here for any questions...
957.
by kens 4y ago
Well, there are opcodes that aren't documented instructions. The 8086 doesn't trap on bad opcodes, so it will execute them and do something. I'm not sure if that's what you mean by "an undefined state". I think
958.
by kens 4y ago
I took a closer look. As you suggested, LEA reg1,reg2 will simply run the micro-instruction "IND→N RNI" without doing any effective address calculation first. Whatever address is in the IND (Indirect) register will be written to t
959.
by kens 4y ago
I was thinking the the READY line might cause problems. If nothing pulls it high, the memory access will be blocked forever. But I haven't looked much at how systems physically implement the bus, so maybe it defaults high.
960.
by kens 4y ago
The 8086 doesn't have virtual memory, so there is no such thing as a pagefault or invalid address. For a memory access, the microcode blocks until the bus interface circuitry completes the memory access. If there's physically noth

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