Development of a transputer ISA board
nanochess.org
Development of a transputer ISA board
1–10 of 15 posts
Re: Development of a transputer ISA board
#2Oh my, transputers and Occam. SEQ and PAR, CHAN and whatever was there to split/assign arrays.
One of my favorite go-to places when seeking peace of mind.
Re: Development of a transputer ISA board
#3Always exciting to see a new Toledo post, but this one is especially inspiring, because it talks about the author's errors that you will probably make too if you don't read the post, and tells how to overcome them. And the activity described is the highly practical activity of designing a PCB this year with the best current free software and getting it built and debugged; the fact that it's an ISA board for a Transputer is fun but not central to the problem-solving process.
I wonder why he used the 74LS00 family instead of 74HCT00, even if he really needed the TTL thresholds? I forget if ISA even requires TTL levels. Is that a question of nostalgia, or is there a practical advantage of TTL over TTL-compatible CMOS in this context that I'm unaware of?
Re: Development of a transputer ISA board
#4we need to bring back the cpu address/data bus pinout on the back of PCs
i want all 64 bits with a write strobe and a 3ghz clock. let me blink leds by bitbanging /dev/mem
Re: Development of a transputer ISA board
#5we need to bring back the cpu address/data bus pinout on the back of PCs i want all 64 bits with a write strobe and a 3ghz clock. let me blink leds by bitbanging /dev/mem
That is less useful than you might expect due to issues of timing skew and signal reflections from transmission-line impedance mismatches.
SCSI was already contending with the termination problem in the early 90s; low-voltage differential SCSI was in the SCSI-3 standard from 01995, 30 years ago, in order to hit 80 megabytes per second over the kind of multidrop (bus) parallel interface you're talking about. That's twenty thousand times slower than the main system memory interface on the latest amd64 servers.
At the point where you already had to go to low-voltage differential signaling to get reliable communication, your bus is no longer a useful GPIO interface for blinking LEDs.
But if you have a 50¢ 16-line GPIO expander chip like https://www.digikey.com/en/products/detail/kinetic-technolog... somewhere on the SMBus the board is already using for things like temperature monitoring, maybe for some other minor interface function, all that's required is to run its GPIOs to test points and document them. Not as fast as the ISA bus but plenty of power for simple digital interfacing.
Re: Development of a transputer ISA board
#6Thanks for the pointers to the autoroute functionality in KiCAD! While wiring manually is quite satisfying, this feeling vanishes quickly when changes in the underlying schematics are required!
Re: Development of a transputer ISA board
#7we need to bring back the cpu address/data bus pinout on the back of PCs i want all 64 bits with a write strobe and a 3ghz clock. let me blink leds by bitbanging /dev/mem
Ironic that this comment is on an article about the Transputer where the entire point was to not use memory mapped I/O, instead only p2p message channels like today's PCIe.
Re: Development of a transputer ISA board
#8Always exciting to see a new Toledo post, but this one is especially inspiring, because it talks about the author's errors that you will probably make too if you don't read the post, and tells how to overcome them. And the activity described is the highly practical activity of designing a PCB this year with the best current free software and getting it built and debugged; the fact that it's an ISA board for a Transpu…
The practical advantage is that the 74LS chips are available in several corner stores at 25 or 35 cents each one, and I preferred the logic to be the same family.
You cannot choose the source, these come mixed from ST, TI, and other manufacturers. I preferred the laser-engraved ones instead of the white ink ones just to have an uniform look.
The crystal oscillator needs something faster so it requires 74F04, and the link communication buffer requires 74F244 or 74AS244. These are more expensive, the 74F are 2 dollars each chip, and the 74AS are 4 dollars each chip.
Re: Development of a transputer ISA board
#9we need to bring back the cpu address/data bus pinout on the back of PCs i want all 64 bits with a write strobe and a 3ghz clock. let me blink leds by bitbanging /dev/mem
I think Raspberry Pis basically give you that via GPIO?
Re: Development of a transputer ISA board
#10Always exciting to see a new Toledo post, but this one is especially inspiring, because it talks about the author's errors that you will probably make too if you don't read the post, and tells how to overcome them. And the activity described is the highly practical activity of designing a PCB this year with the best current free software and getting it built and debugged; the fact that it's an ISA board for a Transpu…
The practical advantage is that the 74LS chips are available in several corner stores at 25 or 35 cents each one, and I preferred the logic to be the same family. You cannot choose the source, these come mixed from ST, TI, and other manufacturers. I preferred the laser-engraved ones instead of the white ink ones just to have an uniform look. The crystal oscillator needs something faster so it requires 74F04, and the…
Oh! I usually think of availability as an advantage for 74HC (maybe not 74HCT) over 74LS, but maybe that's not the case where you are. Local availability is a real advantage.
The electronics parts stores in my town (Morón), which are several blocks from my house, have a fairly limited part selection, mostly for repair purposes. So part availability is a very significant concern. I was shocked to find last month that one of them didn't even have a TL431! But another one on the same block did.
I thought I'd check Digi-Key, but it seems like 74AS244 is even more than US$4 there in onesies: https://www.digikey.com/en/products/detail/texas-instruments.... However, a CMOS 74AHC244 (nominally something like 5.5ns to the AS244's 6.2ns) is only 27¢: https://www.digikey.com/en/products/detail/texas-instruments...
At Digi-Key, the CMOS parts have better availability in this case, but that says nothing about the availability at the corner store.
Thank you for explaining!