Viewing profile — jecel

The simplest processors use one clock per instruction with a Harvard architecture. This allows their control unit to be a combinational circuit instead of a Finite State Machine (a…

I think there were actually 68000 transistor positions. In the ROMs and PLAs not every potential transistor is populated but the missing ones were counted as well. But the number o…

One chip that could be used as a memory mapper for the 9900 (but wasn't in the TI99/4A) was the 74LS670, which was used in the IBM 5150 PC to allow the 8237 DMA chip to access more…

Note that RISC5 [1], a project created as a target for Wirth's Oberon compilers, is a different project from RISC-V [2], a project created at Berkeley which became what is currentl…

We were stuck with 33MHz PCBs for a long time as people kept trying and failing to get 50MHz PCBs to work. Then Intel came out with the 486DX2 which allowed you to run a 50MHz proc…

The naming of processor sizes is the subject of debate. I call a "pure 8 bit processor" one that has 8 bits for both data and addresses. Like the Kenbak-1. But these are so rare an…

Michael J. Flynn, best known in the computing world for his taxonomy of parallel computing (SISD, SIMD, MISD and MIMD), passed away on December 24, 2025

Two years after this booklet, the CRT memory it describes was replaced by core memory (becoming the first computer to use that technology).

Most people are not aware that after the failure of the PS/2 attempt to control the PC market, IBM tried a third time using 7 patents it had for the PC AT (they didn't have any on …

Here is a one hour talk Stewart gave at the 2016 VCF East (Vintage Computer Festival): https://www.youtube.com/watch?v=Ncnje4DdRxE He mentions that the first year it was a live pro…

QNX was my operating system from 1985 to 1988. I also studied it in 2000 for a project that ended up getting cancelled. Initially the actual implementation didn't match the concept…

One issue he mentioned is still true today in Brazil's universities: while in theory you can ask to transfer from one course to another, in practice you have to drop out of your cu…

Actually, the 68000 had one full (all operations) 16 bit ALU and two more simple (add/subtract, so AU might be a better name) 16 bit ALUs so in the best case it could crunch 48 bit…

The 68000 actually had both microcode and nanocode, so it was even further from hardwired control logic than the 8086. In terms of performance the 68000 was slightly faster than th…

They should say on this page that this project has ended. There are some spinoffs people interested in this can look into: https://tinytapeout.com/ https://wafer.space/ https://chi…

The Indy 500 was actually part of the official Formula 1 calendar from 1950 to 1960, though the two series diverged after that. Some Indy features (refueling, changing tires even i…

Though a problem, as you point out, it still happened. The 6800 based SWTPC was followed by 6809 machines what need to have all their software reassembled. On the other side of the…

Thank you for correcting me. I don't know where I heard the story I mentioned.

My own memory of the events (which might be very wrong) was that a new vice-president of IBM semiconductors decided to drop bulk CMOS and focus exclusively on SOI (Silicon On Insul…

The VM in Slang had been previously published as part of the "blue book" (now that is what I call open source!) some 14 years before, and as the paper you linked to mentioned, Mari…

If we label the combinations of the seen and scanned bits as: 00: white 10: gray 11: black then we cam describe it as a very cool variation of the tri-color gc algorithm. https://e…

> Finally, a programing job that AI won't be able to replace. Well, at the recent VCF (vintage computer festival) Midwest they showed a robot using the Altair's front panel to togg…

Exactly, but the text has the same instruction sequence twice and the parent correctly indicated that the first copy should have used "lui" to illustrate the problem you mentioned …

The problem with Self in the 1990s wasn't the lack of sources (I just checked the 1994 Self 4.0 sources and the license looks like the typical BSD one) but the fact that the binari…