Midway 8080 (Space Invaders) EPROM strapping

DarrenF

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I'm working on an SI. It has TMS2716s, which I can't do anything with (write not read) on my programmer. I'd like to program a new set of (regular, non-TMS) 2716 EPROMs. I know I need to re-configure the jumpers/strapping (S1, S2, S3 & S5) to accomplish this. However, the various information I find (schems, old Midway guide, Clay's 8080 page, etc.) give information which is vague, conflicting, confusing and/or incomplete.

Is there a definitive guide to the EPROM strapping configurations on these boards?? Ideally with nice diagrams and/or photos, detailing the jumper positions for a variety of common devices (TMS2716, 2716, 2732, etc.). [Bonus points for explaining the function of each jumper.]
 
I posted a detailed thread (here) about the Taito version. I don't own the Midway version so I couldn't post any photos or details about that version. However they're very, very similar.

There's enough info linked in that thread so you can figure out how to rework the non-address and non-data pins to make a standard 2716 or 2732 work on your board.
 
I posted a detailed thread (here) about the Taito version. I don't own the Midway version so I couldn't post any photos or details about that version. However they're very, very similar.

There's enough info linked in that thread so you can figure out how to rework the non-address and non-data pins to make a standard 2716 or 2732 work on your board.

Thanks for the link to that thread. Helpful. However, I'm pretty sure there's an error with regard to jumper S5. On the Midway PCB, S5 is connected to ROM pin 20, not pin 18. I just very carefully verified that.

Most useful was the fact that I need to tie Vpp to +5 (vice low floating).
I also surmised from the Clay link that /OE needs to be tied low.
I finally just broke down and traced every line and jumper position to it's termination to fully understand what all was going on (like the wacky thing Clay shows, "jumpering" with a solder blob to a +5 trace just above the jumpers, but not really part of the jumper system as designed). I managed to get it strapped for 2716. Thanks.

I can read/write the TMS2716 EPROMs...

You use a Data I/O programmer, or a home-built adapter to provide -5 & +12 and read as regular 2716? I was considering doing the latter, but it seemed too much like work...
 
Data I/O Series 22 with the 064a PROM module. It's great for those old arcane chips like 2704, 2708, and the pesky TMS2716 EPROMs.

I just wish I had something that would read/write 1702A EPROMs.
 
Thanks for the link to that thread. Helpful. However, I'm pretty sure there's an error with regard to jumper S5. On the Midway PCB, S5 is connected to ROM pin 20, not pin 18. I just very carefully verified that.

This is the problem with the documentation on the Midway boards......there's actually two different versions (actually, there's a handful of different "revisions" with minor differences, but two (major) different "versions".

On the early Midway boards (1974 til approximately 1977-1978), S5 strap actually is connected to pin18.......then, at some point around 1977-1978, Midway revised the board to work with 2716's/9316's and re-routed strap S5 to pin 20.

Edward
 
Data I/O Series 22 with the 064a PROM module. It's great for those old arcane chips like 2704, 2708, and the pesky TMS2716 EPROMs.

I just wish I had something that would read/write 1702A EPROMs.

And just what has 1702A EPROMs in it?

This is the problem with the documentation on the Midway boards......there's actually two different versions (actually, there's a handful of different "revisions" with minor differences, but two (major) different "versions".

On the early Midway boards (1974 til approximately 1977-1978), S5 strap actually is connected to pin18.......then, at some point around 1977-1978, Midway revised the board to work with 2716's/9316's and re-routed strap S5 to pin 20.

Edward

Interesting. Precisely why there needs to be a Definitive Guide, including PCB identification and revs. FWIW, mine has a large "2X" on it, and a small "80-900K". I think I'm going to sketch up something in Autocad showing a map of the strap area, identifying each point and trace, and what each is connected to.
 
Interesting. Precisely why there needs to be a Definitive Guide, including PCB identification and revs. FWIW, mine has a large "2X" on it, and a small "80-900K". I think I'm going to sketch up something in Autocad showing a map of the strap area, identifying each point and trace, and what each is connected to.

Yep! As if the strapping wasn't confusing enough........they went and changed the mapping of the straps!

If you throw something together.....let me know if you need any help "filling in the blanks".

Edward
 
Sea Wolf Board 80-900D strapping for 2716's

I did the strapping as documented and game has not worked. See attached. The game had the old 4 chips in it and game booted and worked with a small issue with mines.
 

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did you also change the S6 strapping?
Also remember reading somewhere you have to remove the caps next to the eproms if you change to normal 2716 eproms.
 
Here are some pictures of how I strap for 2716. Ignore the blue wire
 

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I never did make a complete guide to Midway 8080 board ROM strapping, but I did collect some snips from schematics and manuals: (click for larger versions)
 

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I never did make a complete guide to Midway 8080 board ROM strapping, but I did collect some snips from schematics and manuals: (click for larger versions)

A couple more images attached here (due to 5 image per post limit).

I think I once made a drawing of the area of the PCB, showing all of the nearby traces and pads. Must have lost it in the Great USB Drive Failure...

There's some related relevant info here, too: http://www.pinrepair.com/video/seawolf.htm

From a high level, there are two parts to the ROM strapping:
1) setting the ROM size using the S6 jumpers, which connect address lines to the address decoder. If you aren't changing ROM *size* (only *type*) there's no need to mess with these.
2) connecting the appropriate ROM lines (pins 19-22) appropriately using S1, S2, S3 and S5.

For those hip to EPROM pinouts and address decoding, the above should suffice. I still think a more accessible guide to the process would be a helpful thing to put together.
 

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