[Coco] Orchestra 90CC
jcewy at swbell.net
Mon Jan 29 00:35:07 EST 2007
Bob Devries wrote:
> While it's true that the ROM in the Orchestra-90 does do what you describe,
> any third-party and OS9 software does its own handling of the data,
> including the timing between the sending of the data to the ports.
> So unless the new hardware has some way of knowing how much time to insert
> between "packets" of 2-byte stereo pairs, indeed the FIFO will make no
> difference. In fact, I'd rather think that it would completely screw up the
> timing that's necessary for the Orch-90 to work correctly.
And that's what Kevin's original post said. See below.
So how are such things done on PC sound cards? Is there some logic for
pushing the data out at a defined sample rate, or is it all done in
> Regards, Bob Devries, Dalby, Queensland, Australia
> Isaiah 50:4 The sovereign Lord has given me
> the capacity to be his spokesman,
> so that I know how to help the weary.
> website: http://www.home.gil.com.au/~bdevasl
> my blog: http://bdevries.invigorated.org/
> ----- Original Message -----
> From: <jdaggett at gate.net>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Monday, January 29, 2007 6:42 AM
> Subject: Re: [Coco] Orchestra 90CC
>> Adding a FIFO would do nothing to improve the performance. Audio tones are
>> genereated via the software in the 8Kx8 ROM. All the uP does is write to
>> addresses an eight bit data. The writes are to two 8 bit latches whose
>> have a 2R:R resistor ladder to perform digital to analog conversion.
>> The way the progrma works the best method of improvement is to run the uP
>> at a
>> faster speed. Then the software would need patching for timing issues.
>> On 27 Jan 2007 at 20:20, Kevin Diggs wrote:
>>> With all the recent discussion of the 90cc, I thought I'd ask:
>>> If this thing had had a FIFO <b>and some logic to send samples out at
>>> regular intervals</b> how much would that have aided performance? To ask
>>> another way, how much of a burden was it that the 6809 not only had to
>>> compute the samples but also had to deal with sending them out at the
>>> right time?
(Emphasis added, JCE)
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