OBERHEIM SYNTH

Just read through this entire thread, great news! Of course I need to get my drummer working but maybe once its up, if i purchase an eprom, would someone be able to burn another program onto it?



--- In oberheim@yahoogroups.com, "Nicole Massey" <nyyki@...> wrote:
>
> I use Excel for such things because you can set the position very exactly
> with cell widths and such. 
> 
> -----Original Message-----
> From: oberheim@yahoogroups.com [mailto:oberheim@yahoogroups.com] On Behalf
> Of Steve
> Sent: Monday, January 17, 2011 4:44 PM
> To: oberheim@yahoogroups.com
> Subject: [oberheim] Re: The Perf/X units are all the same board! Cyclone,
> Strummer, Drummer plz read!
> 
>   
> 
> 
> 
> I have a Drummer, and tried the cyclone rom in it. What fun!
> 
> To give a little back, I've uploaded the rom image from my drummer, as I
> noticed it wasn't there. I also uploaded a zip file with a Cyclone front
> panel image suitable for printing out and attaching to your Perf/X when the
> cyclone rom is in it.
> 
> I created the front panel in raw postscript, as I couldn't think of an
> adequate tool to do a bunch of "place exactly THIS text at exactly THIS size
> at exactly THIS place on the paper" operations. I didn't work really hard at
> following document structuring conventions, so whether this file is valid
> postscript for whatever tool you might use is questionable. As not everyone
> has access to a postscript printer, I also included a .pdf file and zipped
> them together. (The pdf was created by viewing the postscript file on a Mac
> with the Preview application, then saving a pdf. Hopefully that will be a
> valid PDF for everyone.)
> 
> I also got together with my friend who has the EPROM programmer, and we
> combined the Drummer and Cyclone images (each 32K) into one 64K rom, and put
> a switch on the high order address line. We used a push on / push off
> switch, and we placed it so that you can reach the switch through the unused
> card slot on the side of the case. So now I can switch personalities without
> opening the unit up, although it still requires clearing the battery backed
> RAM.
> 
> This is getting long, but if I don't write it now, I'll probably forget by
> the time someone asks me: I considered putting a 32K RAM chip in to try to
> make each image use a different 8K, so I wouldn't need to clear RAM when
> switching personalities. I don't think a 64K ram exists with a similar
> pinout, so having 32K for each personality isn't an option for a single
> chip. But the images are already designed to look for 8K or 32K RAM, and one
> of the address lines for 32K goes into a CE line on the 8K chip, so there
> are portions of the 32K address space where the 8K chip won't respond --
> it's not just "shadowed" over the whole 32k region. I even investigated by
> disassembling one of the roms a bit, and the result is I believe you need
> additional circuitry to make sure your new ram won't respond at addresses
> where an 8K RAM wouldn't, or the firmware will believe you have a 32K RAM
> and probably overwrite parts of itself. My friend suggested the additional
> circuitry could be a 7400 or a one-of-7 decoder, but I opted not to continue
> down that path as time was short.
> 
> Also of note: space between the board and the front panel is minimal. The
> alternative trick of stacking two chips in the place of one won't fit, at
> least if you don't remove the socket (which may or may not work, I don't
> know). That applies to ROM as well as RAM. In fact, my original ROM had its
> pins trimmed, I assume so it fit lower in the socket; the remaining pins
> wouldn't reach the eprom programmer for reading, we had to stick another
> socket in between to make it work.
> 
> Anyway, thanks to all for pointing out this was possible and providing the
> cyclone image!
> 
> --> Steve Wahl
>