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What are the most expandable, backwards compatible, modern computers?

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David Hess:

--- Quote from: m k on May 17, 2022, 05:29:38 pm ---
--- Quote from: David Hess on May 17, 2022, 04:20:44 am ---
--- Quote from: themadhippy on May 15, 2022, 03:38:36 pm ---only backward compatibility i look for is a proper serial port,yea theirs multiple usb to serial  adapters available,but ive yet to find one that just works regardless of whats hanging off the end.
--- End quote ---

That is my experience with USB to serial converters; they only work properly in the least demanding applications, and often not even then.

My 2011 system was suppose to have a built in serial port, but the level translators were missing. :(

I have gotten by with a PCI serial card, and if I need one now, I will get a PCIe serial card, although I think my 2021 system does have a working serial port.
--- End quote ---

Are these new ports including original I/O instructions?

Windows environment had user programs commanding hardware directly.
Linux has been different from the beginning.
--- End quote ---

The ports I mention here are or simulate 8250/16450/16550 equivalent UARTS with register access through the I/O address space.  Whether accessed directly or through the operating system should not matter.

cdev:

--- Quote from: David Hess on May 17, 2022, 09:39:19 am ---
--- Quote from: Bicurico on May 16, 2022, 01:29:09 pm ---I understand that the x16 mean the bandwidth. So one PCIe lane can have an x16 PCIe card or two x8 cards?
--- End quote ---

Many motherboards with multiple x16 slots use a PCIe bridge to split x16 into dual x8, so that if one slot is used it is configured as x16, but if the other slot or both slots are used, then they are x8.



--- Quote from: Bicurico on May 16, 2022, 06:59:30 am ---But the real struggle is that modern motherboards have only 1-2 free PCIe slots, apart from the one dedicated to the graphics cards.
--- End quote ---

But you can still find new boards at a reasonable price with a split pair of x16/x8 PCIe slots as I described above, plus another x4 slot, and 2 or 3 x1 slots.

--- End quote ---

I always max out on mine, fairly quickly. My current computer is also struggling in the USB area, I just have too much USB stuff. Some of the ports are supposed to have extra power, but this has not helped, it seems. I wish there were better ways to debug this. I have a feeling that some of my post annoying and persistent computer problems are rooted in the USB mess.

Nominal Animal:

--- Quote from: cdev on May 19, 2022, 02:31:45 pm ---My current computer is also struggling in the USB area, I just have too much USB stuff.
--- End quote ---
If you're like me, you have "too many" USB 2 devices, and no USB-2-to-3 "converting" hubs.  (Essentially, when using USB 2 devices, each root port is limited to 480 Mbit/s throughput, even though the root port is an USB 3 one.  This is because USB 2 and USB 3 use physically different transceivers on each port.)

I've also found that for the USB 1.1 (Full speed, 12 Mbit/s max) stuff, using an USB isolator followed by an isolated wall wart (non-grounded, fully isolated USB supplies) powered USB hub, can make a lot of things more stable.  Especially so for stuff I designed myself and am working on :-[.

I'm very eagerly awaiting cheap high speed isolators, now that both TI (ISOUSB211) and Analog Devices (ADUM4165) have released high-speed capable isolator chips.  A simplified version of the Olimex USB-ISO (for USB low or full speed only, no high speed support), with a downstream USB power input port (so that one can use a known good isolated USB power supply (no ground pin!), ubiquitous here in Europe, as long as one does not fall for the crappiest-of-the-bunch ones) to power the device.

In fact, I've already taken a look at the ADUM4165 and ISOUSB211 data sheets, with the intent of making my own heavy-duty isolators with Mean Well medical power supply (say, RPS-30-5 or RPS-45-5) for the isolated downstream.  I'd love to have multiple separately isolated USB 2 ports (with a ganged cable to my computer), but I don't know enough about (isolated) DC-DC power conversion to work out how to do that with just one (possibly not so well isolated) power supply, without risking all sorts of EMI issues.  All of my designs thus far are based on datasheet application recommendations and TI Webench schematics.  (With a microcontroller on the host side of one of the ports, for both monitoring the voltage and power use, but also for disconnecting both the power and the isolated port as needed.  I'm especially interested in how "spiky" the current draw of a specific USB device is, at the sub-millisecond scale.  It would be a very useful SBC test bench, especially if it had isolated, controlled and monitored 5V/9V/12V available for powering the target SBC.)

David Hess:

--- Quote from: cdev on May 19, 2022, 02:31:45 pm ---I always max out on mine, fairly quickly. My current computer is also struggling in the USB area, I just have too much USB stuff. Some of the ports are supposed to have extra power, but this has not helped, it seems. I wish there were better ways to debug this. I have a feeling that some of my post annoying and persistent computer problems are rooted in the USB mess.
--- End quote ---

I have two monitors which each have 4 x USB 3.0 ports, and a USB 3.0 hub which allows me to turn on/off each port.  My keyboard and mouse plug directly into the computer.

Doctorandus_P:
Most MoBo's still have a serial port (or maybe two?) even though it's probably not on the back side. It's often just a 0.1" header tugged away in some corner, and maybe the signals are only TTL without line drivers. But it's not a selling point for a long time so shops don't advertise it. You have to check the booklet of the MoBo you're interested in for this.

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