Wednesday, September 02


Daily News Stuff 2 September 2020

Three Doors Down From The Beast Edition

Tech News

  • Gack.

    I'm not convinced this chart is entirely accurate.  I'm mostly convinced the algorithm producing it said this is fine at some point.

  • Intel has launched Tiger Lake.  (AnandTech)

    Laptop parts only so far, and with a maximum of four cores, when AMD has been shipping eight core parts at the same TDP for months.  But Intel has a small frequency advantage and a potentially larger IPC advantage and will likely run single-threaded tasks around 15% faster.

    I do like how Intel claims "more than a generational increase in performance" when they're comparing with an architecture from 2015.  Yes, well done, have a cookie.

    The chips also have integrated USB 4 / Thunderbolt 4, which should mean rapid adoption of both, and PCIe 4.0.  The chips feature Intel's new Xe graphics, which should be a big update, and support for LPDDR4X-4266.  I was expecting LPDDR5 for some reason, but it's not mentioned anywhere.

    One slight catch: This is purely an announcement.  Not even review samples have been delivered so far.

  • Asus has announced three new laptops based on Tiger Lake.  (Tom's Hardware)

    The most interesting one looks to be the Zenbook S, with a 13.9" 3300x2200 touchscreen.  The other models include a 13.3" 4k OLED display, and a cheaper option with a 14" 1080p panel.

    Screens aside they're all very similar; they use LPDDR4X memory so they're all limited to 16GB of RAM soldered to the motherboard.

    A nice touch is that on all three models the trackpad is a small touchscreen itself.  The Zenbook S, due to its narrower aspect ratio, lacks the Four Essential Keys, but they are present and accounted for on the other two models.


    Shipping in October and November.

  • Speaking of new hardware that looks great that you can't actually buy, Nvidia announced its RTX 3000 lineup.  (AnandTech)

    The RTX 3070 promises 50% more raw TFLOPS than the 2080 Ti at half the price.  Nvidia don't claim that 50% more TFLOPS translates to 50% more performance, and the architecture has changed enough that we can't easily predict how it will run.  But the half the price part certainly sounds good.

    At this point they look like awesome cards, and we'll just have to wait a couple more weeks to find out how awesome.

  • Ah shit, here we go again.  (WCCFTech)

    A stock Radeon 5700XT can earn about $5 per day mining whatevers with minimal effort.  Good thing I wasn't planning on buying a new system any time soon.

  • This is a demo of the Ys II opening credits running on the FM-77 AV.  It looks more like a 16-bit game here than an 8-bit one.

    Not sure exactly which model this ran on.  All had similar CPUs (dual 1.6 MHz or 2 MHz 6809s) but they ranged from 64k to as much as 448k of RAM.  But this isn't showing off the AV's signature 4096 colour mode, and the Ys wiki lists the platform as just the FM-7 which had 64k.

    There are some compilation videos of FM-7 gameplay on YouTube, which show what the system really did - which in turn shows what is possible with something like the Imagine. 

    A couple of things stood out: First, the graphics used a limited number of colours, with dithering to smooth things out.  I'm not sure if the original FM-7 could display more than 8 colours at once, though AV models increased that first to 4096 and later to 262,144.

    Second, three voice FM-synthesis sound is not really that great.  I'm planning at least five voices using wavetable synthesis, with something between 10 and 20 source LFOs. 

    By chaining the LFOs you can get all sorts of combinations of AM, FM, and PWM effects; it's kind of like the way the ANTIC chip could display impossible graphics modes by reprogramming the hardware on the fly.

    Simple examples: Each voice has a sample table and a volume register.  By updating the volume register on the fly, you can build an ADSR envelope in any shape you want - AM synthesis.  A step register controls how fast the voice plays back the sample; by updating that register on the fly you can apply FM synthesis.

    The computationally intensive part is applying the volume calculation, which is the only function that requires multiplication.  Hence the realistic limit of perhaps five voices at full sample rate, with a bunch of other oscillators at lower sample rates providing modifiers.

    Just need to figure out a simple and efficient way to handle stereo.  A sensible approach of having one volume register and one balance register requires four multiplies per sample, which requires four times more hardware than mono.  I'd like to figure out the trick an 80s audio engineer would use to handle that.   Although very likely they'd just do it with an analog circuit, which would be cheating.

    I think for the Imagine emulator I'm going to target an emulated system with 128k each of ROM, RAM, and VRAM, and a single 400k 3.5" floppy (with an emulator option to attach one or two external drives).  That's a lot for 1983 (the year 3.5" drives first appeared), but not entirely unreasonable given that the FM-8 came out in 1981.  64k each of RAM and VRAM and some weird storage like Sinclair's Microdrive might be more period accurate, but I want this thing to be fun to program for, and at some point period accuracy turns into period pain.

    The CPU will be the 10 bit design, emulated running at 3 MHz, with a free-run switch to go as fast as your real hardware can push it (which judging by my current code should be well over 100 MHz).

    480x270 graphics in up to 32 colours from 512, 10 sprites, 5 sound voices as mentioned above.  And a Microsoft Extended Colour Basic compatible compiler built into ROM.

    The FM-7 and my Tandy Colour Computer both ran versions of Extended Colour Basic, since it was Microsoft's standard offering for the 6809.  But I want to make it a compiler to make it easier to get good results.

    I'm thinking of making the core engines of the video, audio, and I/O processors cut-down versions of the Imagine's 10-bit CPU, so they all have a common core set of assembler instructions, plus their own special extensions.  The FM-7 could have three CPUs in 1982, so that's not as insane as it sounds, and would mean less weird stuff for programmers to learn.

    Update: And map the chip registers into the quick page.  That would mean the audio processor could have as many LFOs as would fit in 1k of virtual* registers - still only 5 output voices due to the multiplication bottleneck, but free reign on the modulators.  That would be a lot of fun to tinker with.  The TMS9900 took this approach to its registers back in '79, but didn't have enough fast static RAM for them, and as a result ran like a salted slug.

    Update Two: I have a devious way to do this on a 6809-like chip as long as it has a moderately fast multiply instruction - say 10 to 15 cycles for a 10x10 multiply.  The only problem is it would perform a lot of memory accesses; the sound chip would need its own RAM.  Not a lot of it, but separate from the CPU.

    * Virtual virtual registers, in fact.

  • Oh, and I mentioned bubble memory yesterday.  The FM-8 supported 128k bubble memory cartridges, which are something I could throw into this emulator.  But a bit of poking the archives has largely dissuaded me.  While the access time was good (40ms for the Intel 7110 chip) the data rate was just 100 kbps, slower than a double-density floppy's 200 kbps or so.  And I found an ad for a 128k Apple bubble memory card from 1982 - it cost $895.

    So floppies it is, I think.  Imaginary ones.  The best kind.

Disclaimer: Now I just need to write a self-hosting Basic compiler that targets an imaginary CPU with at least five variant implementations.  What could possibly go wrong?

Posted by: Pixy Misa at 11:47 AM | Comments (3) | Add Comment | Trackbacks (Suck)
Post contains 1365 words, total size 10 kb.

1 Cleanup needed ^^^
Also on which sadly appears abandoned.

Posted by: Mauser at Thursday, September 03 2020 12:44 PM (Ix1l6)

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Apple pies are delicious. But never mind apple pies. What colour is a green orange?

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