9 ms·
486Tang – 486 on a credit-card-sized FPGA board
- spankibalt 1y agoNow put it, together with some other useful boards, into a good non-plastic Amiga 600-sized wedge/keyboard case.
- kristianp 1y agoFrom the reflections section: > x86 vs. ARM. Working with ao486 deepened my respect for x86’s complexity. John Crawford’s 1990 paper “The i486 CPU: Executing Instructions in One Clock Cycle” is a great read; it argues convincingly against scrapping x86 for a new RISC ISA given the software base (10K+ apps then). Compatibility was the right bet, but the baggage is real. By contrast, last year’s ARM7‑based GBATang felt refreshingly simple: fixed‑length 32‑bit instructions, saner addressing, and competitive performance. You can’t have your cake and eat it.
- TehCorwiz 1y agoDoesn’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.
- robinsonb5 1y agoIt 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. 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.
- nand2mario 1y agoYes, for exactly the reason. SDRAM is much easier to work with in retro computing than DDR.
- accrual 1y agoMy first DDR system, an Athlon XP, feels like a very different beast than my 440BX with SDRAM despite being only a couple years newer. :)
- anthk 1y agoI had that with a Geforce2. Or was Athlon 2000. Wait, Athlon 2000 at 1666 MHZ, really fast until the capacitors on a Gigayte motherboard blew up.
- 38 1y ago[dead]
- fabiensanglard 1y ago486? If it has VLB, it can play DOOM well!
- accrual 1y agoIndeed! 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?
- fabiensanglard 1y agoThis is my favorite build to run DOOM: https://fabiensanglard.net/2168/epilogue/ https://fabiensanglard.net/2168/epilogue/
- anthk 1y agoAlso there's FastDoom at Github: https://github.com/viti95/FastDoom https://github.com/viti95/FastDoom
- rbanffy 1y agoI miss Intel's Quark chips. Tiny, cheap, and Pentium enough.
- toast0 1y agoDidn't they have the F00F bug? (Thanks, I keep misremembering) How much more Pentium do you want?
- oakwhiz 1y agoNo, the Quarks did not have the f00f bug, that would have been funny though.
- numpad0 1y agoDidn't they have issues with `LOCK CMPXCHG`(not the 8B)? This is out of my depth and I am not sure, but it sounds similar to the f00f bug. 1: https://en.wikipedia.org/wiki/Intel_Quark#Segfault_bug https://en.wikipedia.org/wiki/Intel_Quark#Segfault_bug
- neerajsi 1y agoYes, they did have the bug with the lock prefix. IOT people at Microsoft got NT booting on the Quark and we ran into that problem. I wound up writing a small tool to patch out all the lock prefixes.
- accrual 1y agoI 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).
- epcoa 1y agoIt wasn’t even discovered until 1997, so no that wasn’t exactly early in the Pentium lifecycle at all. There were multiple models and millions of devices affected.
- SomeHacker44 1y agoSilly 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.
- bobmcnamara 1y agoThere used to be single-chip x86 systems, but I don't know if they went all the way up to 486. You'd see them in early low power portables.
- Frenchgeek 1y agoI'm guessing the ITX-Llama is far less affordable next to reusing a "generic" FPGA retrogaming board.
- privatelypublic 1y agoDefine "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.
- p_ing 1y agoIn Windows, once you're in long mode, there's no 16-bit available to you. You can instead take the DOSBox or other VM route. Linux isn't really relevant given the time frame.
- privatelypublic 1y agoI left it open as to if it was a hardware or OS level item that prevents 16bit. Because I don't know, and don't care to dig that rabbit hole. Also- DOSBox is an emulator vs VMs are hardware, no? I suspect A VM won't fix the "no-op loop for timing" issue- with modern processors' lowest clock being 600-800Mhz before it gets C6/C7'd, 30 years of IPC improvement, and the possibility of the CPU itself optimizing such loops (I'm unsure for various reasons): I expect the UX of "just limit how many scheduler slices it gets" to be nasty.
- p_ing 1y ago> 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. There were probably some off the wall 486 motherboards back then that supported SDR (post-1993...), but those would have been towards the very end of the 486 consumer life cycle. These did exist in the 486 era, where they had the option to run (or had an embedded) 386 using FPM while there was an open 486 socket and the option, but not requirement to run EDO. Anyway, this is someone's project, so they can do whatever the heck they want.
- nand2mario 1y agoAuthor here. 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.
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- hedgehog 1y agoI hadn't heard of this board before, here's a link to a page on the manufacturer's site: https://classic.sipeed.com/tangconsole https://classic.sipeed.com/tangconsole
- aspenmayer 1y agoAh that’s nice. Affordable FPGAs are always welcome. https://archive.is/UD0vH https://archive.is/UD0vH
- p_ing 1y agoA review of sorts - https://youtu.be/ScwZwfS53dE https://youtu.be/ScwZwfS53dE
- devinbernosky 1y agoso this will run half life 2 if I'm not mistaken?
- accrual 1y agoHalf-Life 2 was but a twinkle in Valve's eye when the 486 arch was introduced in 1989. ;)
- ant6n 1y agoCould maybe run HL1. Maybe.
- Philpax 1y agoFor those not aware, this is a reference to an audience comment at the HL2 E3 2003 presentation: https://www.youtube.com/watch?v=4ddJ1OKV63Q&t=200s https://www.youtube.com/watch?v=4ddJ1OKV63Q&t=200s
- system2 1y agoWhen you say "credit-card-sized," I expect the thickness to be as thin as a credit card, too. Isn't the Raspberry Pi credit card sized too?
- sitzkrieg 1y agorpi are, and always have been a little bigger (and much taller) than credit cards. more like altoids tin
- lightedman 1y agoI 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.
- accrual 1y agoThat 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).
- cpgxiii 1y ago> I would love to see ancient tech fabbed out on modern processes. > What's the smallest SOC you could design to run DOOM? Depending on your definition of "modern", more than you think has been done. Intel's Quark were basically 486/Pentium hybrids but fabbed on a fairly modern (at the time) process. While Quark is no longer available as a standalone product, a derivative is part of every modern Intel processor in the form of the Intel ME system co-processor, and it's likely that a number of other Intel products (network cards, QAT accelerators, the ARC GPUs, etc) use them as system controllers as well (Quark essentially came into existence as a "formalization" of the multiple "micro-x86" implementations inside Intel being used as embedded controllers for various non-CPU products). > What would a massively-multicore (gpu-style with multi-hundreds or more of cores) one of these run like? This is close to what the original Xeon Phi was. Essentially 60-ish Pentium cores, with modern SMT and 512-bit vector units added. It worked ... OK? If the software development story had been better (e.g. actual first-class support in GCC) I think they could have been a much bigger success, but the need for ICC back in the ICC-costs-real-money days and initially very expensive hardware certainly held them back. At times I do miss some of their behavior. Arguably a number of the RISC-V-based "AI accelerators" on the market are basically new spins on the same idea: a bunch of small cores, plus large vector/tensor units.
- halyconWays 1y agoI'd pay a decent price for a non-emulated 486 on a credit card sized board, or in a cute little case, with useful peripherals. Something like those Aliexpress mini pocket 386 computers, but 486 is significantly more useful for gaming.
- ColonelPhantom 1y agoOut of curiosity, how much of the 138K LUTs (as well as other resources like BRAM) are in use here? I wonder if there's much room to add fancy peripherals, or perhaps "growing" the CPU to achieve better IPC.
- nand2mario 1y agoIt currently uses 44% of the LUTs and 59% of the BRAMs (out of 340 × 2 KB blocks). The chip itself is fairly large and inexpensive, though performance leans toward the lower side.