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From: TLC (all posts)
Date: 2001-05-06
Subject: Re: Question about SIDCARD schematics/ports

Hi!

> My impressions:
> when I added sid emulation at 0xfd40 only a few programs had sid sound.
> with additional 0xd400 writes, a lot of programs and intros have sid
> sound,
> but I have problem with noise, so I assume the sidcard is not always
> mapped to 0xd400 (maybe it uses some of the rom chip select lines, or
> an flipflop (maybe in the PAL/GAL)).

The answer for your question is that the SID card is _NEVER_ mapped to
$d400.

The SID is _only_ mapped to $fd40 AND $fe80. It is found at both addresses
_at the same time_, as I also stated in my previous post. There are _no_
jumpers on the board whatsoever.

> Added 0xfe80 and disabled 0xd400:
> a lot of programs now do not have sid sound again.

Because, _most_ programs were _not_ designed for the SID card in particular.

The fact that a lot of post-1990 programs make intensive use of the $d400
page is that they indeed feature original C64 musics. But these were in fact
_not_ planned to play on _any_ additional hardware but they play using a
'music converter routine'. The original C64 player code was just not touched. There used to be another programs, 'music converter routines'
embedded somewhere into the code that read the $d400 page after every run of the music player, and then emulated a "SID" by software, using the values found there.

BTW, the programs you mentioned should indeed play some music -- without any additional fiddling --, provided that you implemented good TED sound emulation.

If you'd like to implement something that takes advantage of this fact, then the answer is probably an original (~1Mhz clocked) SID emulation @ $d400 --
but this will definitely not be a "SID-card emulation" whatsoever. If you implement such a feature, make sure that the TED sounds can be disabled at the same time (probably, with the same setting). Keep in mind that some music converter routines did also write accesses to the $d400 map, so certain programs will sound strange when the TED sound is replaced by an emulated SID at $d400.

Once again, the musics that you find in programs with $d400 base have nothing to do with the SID card.

> Do the sidcard have separate sound outputs?
> And was the ted sound hearable over these separate output?

Yes, and no. There is a switch, with which you can direct the SID output either to the EXTIN of the Plus/4 (so the SID sound gets mixed with the TED sounds and appears on the Plus/4 sound outputs) or to a 3.5" jack connector.

(BTW, there is also another 3.5" jack on the card, as sound input (for the SID EXTIN)).

> There was also a joystick port on the sidcard!?
> Maybe to allow an additional standard c64 joystick with dsub9 connector?
> Or to allow use of the vc20/c64 paddles?
> Were there some programs relying on the joystick/paddles?

Yes. I think Solder has included that for the 'completeness sake'.

The joystick port has all lines found on the C64 joystick port, even POTX and POTY are included. So besides the paddles, even a C= 1351 mouse is possible to use. The only problem with that: the SID runs at the single clock of the computer (17.734470Mhz / 20 in PAL) that is slightly less than the original clock of the SID, so a few unexpected happens can occur,
especially with clocked devices (like the 1351). The smaller clock also affects all SID operations, including the oscillator frequencies and ADSR speed.

(For a _SID_ emulation, the nominal clock should be either of the original C64 clocks. For proper _SID_card_ emulation however, the slower clock should be taken into account (the thing should be clocked at 885Khz instead of
985). Another short addition is, that the SID-card was only able to handle the newer, 8580 SIDs).

I doubt if programs made extensive use of that joystick port. A very few programs (and I presume: from Synergy) probably could.

> Did all the sidcard users buy boards/gals or complete sidcards?

AFAIK Solder has only sold complete SID cards.

Best regards,

Levente