On 28 Apr 2021 at 23:24, tom ehlert wrote: > > > ...the board format does not matter much. > > It's the CPU model/generation that matters. > > NOT. AT. ALL. > > each Intel/AMD CPU produced the last 20 years is able > to execute the same way that the previous versions did. > ...okay, apologies, it is not my intention to start a flame war :-)
I agree that in terms of instruction set and memory/addressing modes supported, even the most recent x86 CPU's can still run 16bit DOS-era code. What I meant by "CPU" in this case was the broader platform that goes with it. The chipset, the "evolutionary generation" of the "firmware". Speaking of the chipset, I'm referring to legacy peripheral hardware, at least the presence of a decent "legacy SuperIO" chip in moderately dusty history, vs. the gallop towards newer and speedier USB and PCI-e standards. Yes I'm aware that modern "firmware" still tends to facilitate DOS operation by providing keyboard and mouse services (or even PS/2 controller emulation through SMM) on top of physical USB hardware... Think about software that's written for slow x86 CPU's, and fails miserably on anything faster than a couple hundred MHz - and no, it's not just the Borland Pascal CRT library, there are others of this class. There are games that kind of relied on CPU speed in some ballpark, otherwise the animations are too fast to even notice etc. Older BIOSes used to allow you to mess with ISA MMIO windows available for use with your peripheral devices - with the demise of ISA, BIOS config options related to memory space between 640 kB and 1 MB have quickly vanished, and the "firmware" takes liberty at using this range for whatever option ROM's it sees fit, thus making any "conventional memory volume tuning" pretty problematic. In all those respects, the CPU generation is a pretty good predictor of what kind of a "platform" you get around it. Speaking of tiny x86 platforms, I'm wondering what happened to the Intel Quark. Initially this looked like a contender against the DMP Vortex, but only until you looked at the peripherals present on the reference motherboards with Quark. In terms of peripherals, it's like comparing a traditional large Legoes kit of late eighties (Vortex) to a slick and glittery Tamagotchi (Quark). I do feel guilty of promoting a particular vendor / product line, but let me repeat this link that I sent yesterday: https://www.icop.com.tw/product_list/44 Notice that the particular board format is a proprietary 100x66 mm, called "tiny module" by ICOP. This is not a PC104 format - which means lower price. Anything that has a PC104 connector on it is automatically +50%. The "tiny module" form factor is not significantly larger than an RPI, and while it does not have the perfomance of an RPi, in terms of tinker-friendly interfaces, it probably gives the RPi a run - especially if you're fond of the 486-era legacy x86 style. Some models have an SD slot, some have an onboard SPI flash disk to boot from. The SoC has got an on-chip USB EHCI and an on-chip 100Mb LAN. I personally prefer the Vortex86*DX* era hardware by ICOP, exactly for its 486-ish features and peripherals. The nominal clock tends to be 600 to 800 MHz, but can be underclocked down to 1/8th of that, in the BIOS (or programmatically). The VDX boards have a discrete SIS/XGI Z9s PCI graphics with a dedicated 32MB VRAM and a pretty good VESA BIOS ROM (a rich selection of classic SVGA video modes). I don't like the Vortex86*SX* as much (for obvious reasons) and I don't like the newer developments from DMP as much either, because of the "modern direction" these have taken. The VDX hardware doesn't have nearly the sort of problem with heat that an RPi tends to have, without additional heatsink upgrades. That said, even the cheapest Vortex motherboards are still more expensive than an RPi. The larger Vortex board formats, i.e. PC104 or 3.5" biscuit, have IDE (or SATA) or CompactFlash coupled to an IDE channel, and other goodies - those board models obviously cost more. But, at least you have a choice, and it's still classic 486 era busses and interfaces. I'm wondering why ICOP never produced say an ITX form-factor motherboard with an ISA slot, or a full-length ISA+PCI PICMG board. It probably wouldn't pay off (pay for the R&D) because retrofits/refurbs of full-scale computers in production use are really few and far between, and just nostalgia probably wouldn't generate enough sales. A side note on CPU clock rate: in the golden era of EIST, before TurboBoost, it was fairly easy to poke some EIST-related MSR to underclock the CPU core on the fly. So we're speaking say Pentium 4 or Pentium M up to Core 2 45nm. Even that way, you typically wouldn't get lower than say 600 MHz to 1 GHz on a particular CPU, where the IPC was already a multiple of what the old Pentium MMX would provide... so the EIST underclocking is not enough to dodge the "Borland Pascal CRT limit", but it's a neat trick nonetheless, able to save some watts of consumption and heat on those older CPU's, and even viable for some less severe cases of "software depending on the CPU not being way too fast". I believe I used to play with this using Rayer's CPUID command-line utility: http://rayer.g6.cz/programm/cpuid.zip ... though if memory serves, this meant manual poking of some MSR's (no user-friendly cooked functions for that) Frank _______________________________________________ Freedos-user mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freedos-user
