EclaireXL

Have a dual 8250 working, though it doesn't fit in the smaller boards. Investigating why, memory or logic...

Logic utilization (in ALMs) 9,808 / 9,430 ( 104 % )

600 alms each, will use mono sid I guess. Or make it a generic and enable on the larger boards?

Also got this potential USB sharing, that'd save 750 ALMS. Each request/reply is host initiated, so no reason can't share one. Keepalives would need to go to both ports. Not sure how complex that'd be! Perhaps I plumb the output to both, with a mux for when I send explicit in/out requests?

Actually the issue with fitting in v2 is block ram, not ALMs. Though its always good to save ALMs!

The sid tables take 14KB each. So for stereo sid its 28KB. Anyway I do not even have 14KB to spare on v2...

I loaded the tables in to octave to take a look.

• Not a simple curve
• Lots of zeros, >80% in some cases
• Quite a lot of dupes

dupes:

log2(numel(unique(ps)))

ans = 6.5699

log2(numel(unique(st)))

ans = 4.7549

log2(numel(unique(p_t)))

ans = 5.8074

log2(numel(unique(pst)))

ans = 4.5850

zeros:

sum(ps==0)/numel(ps)

ans = 0.63379

sum(st==0)/numel(st)

ans = 0.86743

sum(p_t==0)/numel(p_t)

ans = 0.58545

sum(pst==0)/numel(pst)

ans = 0.89331

Wondering about some kind of bit map of unpopulated locations (reducing locations) or a 2nd lookup layer (reducing bits)

Also wondering if the clk frequency is important (not enable), I see some state table increment on every clock, which is reset on enable

It sounds good to me, but not sure what it is meant to sound like!!

Did some research over the weekend. Generating these isn't a terribly trivial problem!

I tried for some time to generate in matlab. I came up with a pretty good solution for wave 3: triangle + sawtooth. Actually its sawtooth + 2 sawtooth since the triangle is inverted. Anyway this worked pretty well:
tmp = zeros(size(a));
for k=1:12
pre =k-4;
post = k;
if pre<1
pre = 1;
end
if post>12
post = 12;
end
idx = pre:post;
if a(idx) == b(idx);
tmp(k) = b(k);
end
end
i.e. and and if in conflict, ground the 4 adjacent bits.

Was struggling with the pulse + triangle one, now come up with an easy answer for that one yet!

Anyway found some description of what is going on in the libsidplayfp + some functions to generate:
libsidplayfp-2.0.1/src/builders/residfp-builder/residfp/WaveformCalculator.cpp

Also the wave files are here:
https://bel.fi/alankila/c64-sw/combined-waveforms/sidwaves/

I have implemented my own better sid core now which I will back-port to Eclaire.