Could the 8-bit chips have had a place in the ST?

kool kitty89 · December 6, 2010

Would it have made sense for Atari Corp to make use of the existing Atari Inc custom and off the shelf support chips being stocked/produced for the VCS and A8 for the ST arhitecture in place of some/all of the off the shelf support chips used?

Ie could one (or multiple) POKEY, RIOT, PIA, 6507, or 6502C chips have been useful and cost effective (taking licensing/IP ownerships/existing stock into account) in the roles of the ST's ACIA, MC68901, YM2149, HD6301, etc?

In those terms it seems like the 6502C+RIOT and dual POKEYs would cover most of the functionality of the 6301, ACIAs, and YM2149 do and other things they don't (with POKEY and RIOT you've got a lot of timers to use -more than the 68901 and 6301 offer, more audio capabilities and linear DACs, possible use of POKEY's Sertial I/O though I'm not sure if that could be used for MIDI and probably wouldn't be useful for RS232 -potential for an SIO based interface though, plus POKEY's ADC capabilities though they may not have been useful at all -not sure if the POT inputs would be fast enough to be useful for digitizing audio: if anything it would obviously be using the fast POT scan mode for up to 15.7 kHz 8-bit recording -though without an 8-bit DAC you'd have no way to play it back internally at full quality).

In addition to the initial cost factors, there's also the potential to consolidate any of the custom/licensed chips later on (which wouldn't be possible with off the shelf chips -without additional licensing), and short of that they could have used cut-down packages for any ICs that didn't need the full original functionality. (though without shrinking the dies, you probably couldn't go below a 24-pin wide DIP for any of the chips as anything below that drops to narrow DIPs -POKEY would be an obvious one to cut down if certain things weren't used, especially given you'd likely be using dual POKEYs -even if the analog ports had some use you'd likely only need one or 2 per chip among other things)

If you happened to have a 2 MHz 6502 and at least one POKEY onboard and the 6502 wasn't monopolized by I/O duties, that could have also made for a very useful route for PCM playback using POKEY's DACs and interval timers (or using software timed PCM, but 650x ints are fast in any case) and allow use of 4-bit multi-channel PCM independent of the 68000. (not Amiga quality, but a reasonable approximation and with independent channels you could control pitch purely via playback rate rather than scaling/resampling to a common output and probably competitive with if not superior to the software MOD players seen on the vanilla ST -resolution limited to 4 bits per DAC but potential for higher rates and lack of artifacts from mixing and conversion to YM audio) Of course, to make the 6502 useful for such, you'd need access to main RAM and not just the RIOT scratchpad or hardwired ROM as the 6301 had. (unless the 6301 already does have access to main memory)

If any of that was possible or attractive from an engineering standpoint for the ST, perhaps it would still have been impractical in the context of the ST/RBP's development state by the time TTL bought Atari's consumer properties in '84. (otherwise perhaps it was never seriously considered due to tunnel vision on completing the existing design as planned)

Edited December 6, 2010 by kool kitty89