ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
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<andlabs>
ok
<andlabs>
can VHDL program in timings?
<ej5>
sort of, it's quite complicated. the cards are not designed using synchronous logic. it's the old-school style that mixed asynch and synch
<ej5>
but more or less the FPGA must be done synchronously. so the designs i have come up with are a compromise. i'm trying to match the original card as closely as i can, but i have had to make changes.
<andlabs>
oh
ZirconiumX is now known as Lofty
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<andlabs>
ej5: wait you're also emulating the CRTC?
<andlabs>
I was imagining something where you provided a real CRTC and RAM and ROM
<ej5>
no, it's all emulated, including the CRTC
<ej5>
i'm curious to see how well it does with some of the weird composite color modes, where the character height is odd
<ej5>
it already works fine in graphics mode, and the CRTC is programmed with a character height of 2
<ej5>
the original CGA did this so that the a row address bit could serve as an additional memory address line
<ej5>
this is the reason why the even lines start at 0x0000 and the odd lines start at 0x2000
<andlabs>
oh
<andlabs>
I mean yeah
<andlabs>
that deisgn is fair enough =P
<andlabs>
and fully understandable
<andlabs>
I'm just thinking about the viability of an alternate approach
<ej5>
with a real 6845, RAM, and maybe a few buffers, and CPLDs to replace the logic?
<andlabs>
yeah
<andlabs>
or even the CPLD to replace the buffers too
<andlabs>
"everything that isn't proprietary"
<ej5>
you'
<ej5>
ack
<andlabs>
it's probably not worth it
<ej5>
you'd need to replace the DRAM with something, maybe SRAM, and then change how the addressing works
<andlabs>
(cc ej5 and possibly also cr1901_modern)
<ej5>
heh i watched that video not 20 minutes ago
<ej5>
i think i have an EGA Wonder, i should fire it up and experiment.
<andlabs>
I wonder what the compatibility errors are =P
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<Foone>
andlabs: I want that prototype card. I have some other cards from them but none that fancy
<Foone>
also I already emailed Adrian about the SIP memory. I seem to recall Excess Solutions down in San Jose has some, so I offered to grab him some next time I'm there
<andlabs>
lol
<andlabs>
that's the ebay seller I bought my uhhh
<andlabs>
AlphaStation from
<andlabs>
immediately before a far less expensive one was listed by someone else but whatever I just wanted to get it done
<Foone>
ahh, I know that stage well. the "fuck it, I don't care about getting a good deal, I just want it to be HERE so I can move on" phase