Sunday, August 30
Dream A Twelve-Bit Dream Edition
- Went out to the shops this evening. I self-isolated for a couple of weeks because I caught a cold - somehow - then for another week because I was feeling lazy, so it was time to emerge from my burrow.
Things were pretty normal. No shortages, except for the stuff that was half price, and no purchase limits. About a third of the people were wearing masks, though about a third of those were only sort-of wearing masks.
- I've nearly completed the programming model for the 10 bit Imagine and 12 bit Dream systems. The 10 bit model is positioned mid-way between the Z80 and the Z8000, with a dash of 6309 because the 6309 is really nice.
The 10 bit mode is a proper subset of the 20 bit mode, so there's no switching between the two; 10 bit code runs unaltered in 20 bit mode, and if you need to add a couple of 20 bit instructions here and there it just works.
The 12 bit system is a design I dreamed up a long time ago, half-way between the 6809 and the 68000. It has registers from A to Z, just because I could.
They're deliberately similar so I can easily target both with the same compiler. I haven't yet looked into 9, 11, or 13 bit designs. The 13 bit system will be as weird as logically possible, perhaps a cut-down iAPX 432 or Linn Rekursiv.
But that will be later.
I also need to figure out the rest of the hardware. I have a handle on the video controller, thanks to the existence of the Atari ANTIC chip and the NEC 7220. But I haven't yet figured out what exactly to do for sound. I want wavetable synthesis, because that's a real thing (the Apple IIgs had it) and purely digital, so I'm not faking an FM synth like the Commodore SID.
The first couple of commercially available DSPs in the early 80s (the NEC 7720 - just to confuse you - and the Intel 2920) didn't have hardware multiply and ran like snails. But a snail might be good enough here. Let's see: 10 voices, stereo, times a sample rate of whatever my imaginary HSYNC is... 18.75kHz, that's fine. 375,000 samples per second. So I would need to sustain one 10x10 multiply every eight cycles at 3MHz. That's not possible with software shift-and-add, but is probably feasible in hardware, if the hardware is feasible.
Oh, right, the 8086 had hardware multiply. How fast did that... Oh. A minimum of 70 cycles for an 8x8 multiply. Might need to rethink this part.
Update: The Z8000 was about twice as fast as the 8086, completing a 16x16 multiply (rather than 8x8) in 70 cycles.
The TMS32010 came out in 1983 and included a hardware multiplier that could complete a 16x16 multiply in 200ns - one cycle at 5MHz. Only problem is that it cost $500 at a time when an entire C64 cost $300.
By 1987 it was being used in toys, but in 1983 TI shipped a total of just 1000 units.
- When I was looking into doing this in hardware last year I considered using real components - 6809, Z80, and/or 6502. When looking up component availability for these 40-year-old chips, one name kept popping up: Rochester Electronics.
I'd never heard of them and wondered if they really had all this old stock. Turns out yeah, they kind of do. (Wikipedia)
They have over 27 billion components in stock, counting both complete devices and unpackaged dies. They also have a license to manufacture some old chips from the original designs, including the 6809.
- The Radeon RX 5300 sounds like it should be terrible but probably is just fine. (Tom's Hardware)
The 5700 is their mid-range gaming card - AMD don't really have a high-end gaming card in their current lineup, with Big Navi yet to make an appearance - with the 5600 in the low-mid range and the 5500 for entry-level gaming.
So two notches below entry-level means bad, right?
Maybe not. Seems to be a cost-reduced 5500, with 3GB GDDR6 RAM vs. 4GB, but the same 22 CUs. The current Ryzen 4000 APUs by comparison have 8 CUs, and they're just fine for light gaming, so this won't be bad at all.
Looks like it missed one mark, with a 100W TDP. At 75W it could run on PCIe slot power alone; instead it will need an additional 6-pin power lead.
- Samsung have officially announced their 980 Pro SSDs. (WCCFTech)
These are PCIe 4.0 models that really use the PCIe 4.0 bandwidth: Up to 7GB/s reads. up to 5GB/s writes, up to 1M IOPS.
Maximum capacity is only 1TB, which is kind of dumb. Are these MLC? Is that wh... Nope, TLC. Or as Samsung calls it, "3-bit MLC".
- Hacker News has fallen over. So no quirky little items for you today. (A lot of it makes its way to Reddit as well, but it's harder to find there.)
- Google wants to break the web. (Brave)
I mean, so do I most days, in the sense of throwing a virtual brick in its direction, but Google could actually screw things up in a major way.
This is about the big G's proposal of Web Bundles which are bundles of... Stuff.
The benefit of this is that one pre-compiled bundle can be downloaded faster than a hundred or two hundred pissy little files. The front page of Reddit, for example, makes 158 requests even with ads and trackers blocked.
The downside of this is that we already had this and it was called Flash.
Ratchet and Clank Extended Gameplay Trailer of the Day
This looks amazing. But also kind of dull. But then I'm not the target audience.
It does effectively show off the PS5 hardware. And the Xbox Series X is even more powerful, as far as graphics rendering goes.
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