HN Distilled

Essential insights from Hacker News discussions

486Tang – 486 on a credit-card-sized FPGA board

Original Article

Hacker News Discussion

Here's a summary of the themes expressed in the Hacker News discussion, along with supporting quotations:

DDR vs. SDRAM in Retro Projects

A significant point of discussion revolves around the choice of memory technology (DDR vs. SDRAM) for retro computing projects, particularly when interfacing with FPGAs. DDR3, while modern, presents challenges for low-speed retro implementations due to its minimum speed requirements. SDRAM, on the other hand, is seen as more flexible for these applications.

  • "Doesn’t DDR just stand for Double-Data-Rate? So you implemented basic DDR on top is sdram. Not a bad approach, just wanted to point it out." - TehCorwiz
  • "It does, yes. But the DDR RAM available on the target board is DDR3 which is actually quite inconvenient for retro projects for a number of reasons. Quite apart from the increased complexity, the most important difference is that there's a minimum speed as well as a maximum speed for modern DDR RAM, which means there's usually quite a narrow window of achievable clock rates when getting an FPGA to talk to DDR3." - robinsonb5
  • "I suspect that's why the author chose to use the DDR for video: It's usually easy to keep plain old SDRAM in lockstep with a soft-CPU, since you can run it at anything between 133MHz (sometimes even more) and walking pace, so there's no need to deal with messy-and-latency-inducing clock domain crossing. Streaming video data in bursts into a dual-clock FIFO and consuming it on the pixel clock is a much more natural fit." - robinsonb5
  • "Yes, for exactly the reason. SDRAM is much easier to work with in retro computing than DDR." - nand2mario
  • "Obviously, at the time of the 80486, DDR didn’t exist, so SDRAM is a natural fit. Neither are a fit, SDRAM was a Pentium/K-6 standard (PC66); the DIMMs ran faster than a non-OC'ed 486 bus, which ran at half the clock of the CPU. 486 "natural fit" would be FPM or EDO, if you wanted to be era-correct." - p_ing
  • "You’re right—EDO or FPM would be correct for the era. But as others have noted, DDR3 is fundamentally different from early 1990s memory, and it simply won’t run at the very low clock speeds of a 486. SDRAM, on the other hand, behaves in a way that’s much more comparable to the memory used back then." - nand2mario (Author)

Nostalgia for Older CPUs and Architectures (486, Pentium, Quark)

There's a strong sense of nostalgia for older processor architectures, particularly the Intel 486 and early Pentium chips. Users recall specific experiences and appreciate the simplicity and character of these chips. The discussion also touches on the distinct feel of systems from different eras.

  • "My first DDR system, an Athlon XP, feels like a very different beast than my 440BX with SDRAM despite being only a couple years newer. :)" - accrual
  • "486? If it has VLB, it can play DOOM well!" - fabiensanglard
  • "Indeed! I have a 486 DX4-100 that is my favorite DOOM system. It has an S3 805 VLB card currently, fast enough. Do you have a favorite VLB card for the 486 or DOOM?" - accrual
  • "I miss Intel's Quark chips. Tiny, cheap, and Pentium enough." - rbanffy
  • "Didn't they have the F00F bug? (Thanks, I keep misremembering) How much more Pentium do you want?" - toast0
  • "No, the Quarks did not have the f00f bug, that would have been funny though." - oakwhiz
  • "I believe the F00F bug was patched out pretty quickly in the Pentium's B2 stepping. Nevertheless, some OSs still have mitigations if they detect an affected CPU (e.g. OpenBSD)." - accrual
  • "It wasn’t even discovered until 1997, so no that wasn’t exactly early in the Pentium lifecycle at all." - epcoa

Alternatives to FPGAs for 486 Emulation

The discussion explores whether dedicated, smaller CPUs or SoCs could be used instead of FPGAs for projects aiming to emulate or replicate 486-era computing. While modern CPUs can often run 486 code, issues with timing accuracy for older software are highlighted.

  • "Silly question. Are there any 486-compatible small CPUs that could be embedded into a project instead of using an FPGA? Given that AMD, Intel and others have the ability to make 486-compatible processors currently, I would have thought you could just buy a CPU or SoC to run 486 code." - SomeHacker44
  • "Define "486-compatible." As far as I know even intel's newest cpus can run 486 era 16-bit stuff in hardware. But, a plain answer: Via Eden boards. still use north/southbridge architecture, and are from the mid 2000's. It's just modern Windows/Linux that have discontinued the ability. Or, perhaps you have 16/32 and 32/64 and are unable to do 16bit on 64bit machines- which still boils down to "operating system." By far the biggest issue though is that even the Via Eden processor is significantly faster than a 486- and lots of software (especially games) from that era used no-op instruction loops for timing and timers. This results in games like The Incredible Machine's level timer running out in half a second or less." - privatelypublic
  • "Intel did have a product like that but it's been discontinued: https://en.wikipedia.org/wiki/Intel_Quark" - ThrowawayR2
  • "Vortex86 is probably the closest thing to what you are looking for." - zokier

Project Affordability and Availability

The cost and accessibility of specialized retro computing hardware, such as the "ITX-Llama" system mentioned, are discussed. The general sentiment is that affordable FPGAs are a welcome development for hobbyists.

  • "I'm guessing the ITX-Llama is far less affordable next to reusing a "generic" FPGA retrogaming board." - Frenchgeek
  • "Any idea when Pixel86 is going to be available again or how/where to get an ITX-Llama system?" - vascocosta
  • "I hadn't heard of this board before, here's a link to a page on the manufacturer's site: https://classic.sipeed.com/tangconsole" - hedgehog
  • "Ah that’s nice. Affordable FPGAs are always welcome." - aspenmayer

Modern Fabrication of Ancient Tech

A user expresses interest in the idea of fabricating ancient technological designs using modern manufacturing processes, considering aspects like power consumption, speed, and potential for massively parallel architectures.

  • "I would love to see ancient tech fabbed out on modern processes. What's the smallest SOC you could design to run DOOM? What power envelope would that consume (exclusing display/speakers/etc.) At that size and (optimized) transistor count, what speeds could we realistically achieve? What would a massively-multicore (gpu-style with multi-hundreds or more of cores) one of these run like? Every time I see a project like this, these thoughts run through my head." - lightedman

The Evolution of x86 Architecture

The discussion briefly touches upon the conceptual divergence of the x86 architecture after the 486 when it shifted to superscalar designs like the Pentium.

  • "That is a cool idea for sure. It's fun to imagine where the original x86 platform ({80,2,3,4}86) would have gone if it hadn't been remade with the Pentium (superscaler)." - accrual