Repository navigation
Replies: 4 comments 6 replies
|
Okay, after further research, it seems like in an ideal world what I want is a 28 pin Fire with 7 inputs out the top side that could connect to the 7 extra CS pins on the other ROM sockets and firmware for the One ROM to know how to handle that. And from what I gather there's work happening in the firmware direction, but there probably aren't that many inputs available on the 28 pin Fire. It seems like the next best plan is a single satellite board with a 28 pin setup to plug into Bank 0 of my board and a 32 pin socket for a Fire 32 emulating a 27c040. Then add an encoder chip with 7 inputs to encode the 7 CS lines from the other ROM sockets into the high 3 address lines. Then just cat my ROM files together in the right order and problem solved. Duplicate this for the other rail (since we're 16 bit.) Reasonable? If a 28 pin Fire had just three inputs available, then the right answer seems like making a custom satellite board that plugs into the SECOND 28 pin ROM socket beside a 28 pin Fire in Bank 0. It would only have an encoder chip on it and then would just need six wires going to the other banks (since it could get one from the socket it's plugged into, along with power and ground) and then it's 3 outputs could jump over to the Fire 28. But then that obviously requires firmware on the Fire 28 to support that (I'm assuming there's more than enough Flash space for all that data, too). |
|
Okay, last thing. It seems highly unlikely that a Fire 28 has 7 available inputs, but it's possible it has 3. Does it have 3? And if so, where are we on firmware that might support those being used as additional address pins and being able to serve up to seven additional ROM images that way? This option would be cake to prototype up for testing and then could turn into a very generic PCB for folks in this situation. |
|
A few things here:
The One ROM firmware indexes a table by the raw sampled pin word, so taking eight selects directly would mean a 16MB table. Encoding them to three bits is what makes it 512KB and doable from a single One ROM. The CLI would probably be easy to mod to be able to take 8 images and stick them together for you. I've already introduced some image de-interleaving support, so could add these together for a single programming action from a single 16-bit image to both One ROMs simultaneously. |
|
Okay, that answers what I needed, thanks. I'll probably design a PCB for the 32 pin with the encoder on it and headers for jumper wires and then just use two of those, one for each bank. I'm mostly using AI to generate custom ROM images as it is, and it's probably going to be fine at generating me one ROM image for the bigger ROM that'll just work, so no need to add anything to the CLI unless you just want to. I'll definitely be posting this work for others to use (I may do a decent little run and sell some just because, but it'll be more to offset my costs than to make money), too. |
|
Another question...in my particular application I plan to use a single OneRom on my custom PCB with a 74148 and jumper wires to the CS on the other chips. Basically swapping out 8 27C512's for one 32 pin OneRom Fire setup in 27C401 mode and with the 8 images concatenated. Assuming I designed my board right and hook up the CS lines right, I believe it'll work. The problem is physical assembly. The ROMs I'm eliminating are in the bottom of a board stack. And everything fits except I can't install the jumpers on top of the OneRom. Now, I've read the document on ROM image swapping, but it's still not clear to me what to do if I just want the one image on my OneRom. I think I can just leave those jumpers off and do nothing, but I want to be sure I don't need to just install a soldered jumper in one location. |
If you're just putting a single image on One ROM, and don't need to switch between that, then you don't need to expose these header pins at all. Essentially, One ROM uses the 4 right hand jumper pairs as bits of a binary number. No jumpers = boot slot 0, right hand jumper closed = boot slot 1, second right hand jumper closed = boot slot 2, etc. |
|
Confirmed today that my ROM eliminator board works to replace eight by 27c512 with one 27c040 as well as with one OneROM Fire 32 acting as a 27c040 (yes, confirmed with BOTH a real ROM and a OneROM because I'm not a trusting soul). Claude very much screwed up the first PCB design by LITERALLY DEAD SHORTING POWER AND GROUND, but in Claude's defense...there is no defense. It was the stupidest thing I can imagine. But somehow, some way, I didn't actually connect anything before figuring that out. And it was done in a way that was totally fixable by cutting one trace. Amazing. And fortunately I never published that work, so the update can be published first. That's why I don't publish until I can test! Anyway, thanks for the OneROM. Now I'd kill for the ability to network OneROMs easily and have a single, more expensive, OneROM that had wifi or at least Bluetooth so we could do wireless updates of many OneROMs in one system. As of now, though, I think I have this board (A Race Drivin' arcade driving game from circa 1990) to the point that with 4 OneROMs you can upload custom code to it. And we have a full track editor as well as some other very cool goodies coming soon, one of which may just be the ability to play the game in full 3D using Apple Vision Pro goggles. Which is cool, but something probably four people will ever do. But custom tracks is something a lot of people are interested in, but probably nobody cares if it takes burning and replacing 18 ROMs. heh |
|
Very cool! My plan for networking is Airfrog, which there's some stuff about, but it needs a new rev for the current One ROM Fires (to match the header). It's a tiny hat that plugs on the header pins, being powered by One ROM and adding WiFi to it. I need to get back to it, but there's so much to do with plain One ROM! |
|
Is there a channel to get updates pushed when you do release new things?
—Donnie
On Oct 1, 2026, at 1:26 PM, Piers Finlayson ***@***.***> wrote:
Very cool!
My plan for networking is Airfrog, which there's some stuff about, but it needs a new rev for the current One ROM Fires (to match the header). It's a tiny hat that plugs on the header pins, being powered by One ROM and adding WiFi to it. I need to get back to it, but there's so much to do with plain One ROM!
—
Reply to this email directly, view it on GitHub<#302?email_source=notifications&email_token=ALYLE6SKEOR75I3KTVE4UED5R2HUBA5CNFSNUABIM5UWIORPF5TWS5BNNB2WEL2ENFZWG5LTONUW63SDN5WW2ZLOOQXTCOBXGAZDINRWUZZGKYLTN5XKMYLVORUG64VFMV3GK3TUVRTG633UMVZF6Y3MNFRWW#discussioncomment-18702466>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ALYLE6VIOAWDLEM5QMHTROD5R2HUBAVCNFSNUABIKJSXA33TNF2G64TZHM4TONRSGU4TKMJTHNCGS43DOVZXG2LPNY5TCMBXGQYTSMRRUF3AE>.
You are receiving this because you authored the thread.Message ID: ***@***.***>
|
|
youtube is best: https://www.youtube.com/@piers_rocks |
Uh oh!
There was an error while loading. Please reload this page.
So I have a vintage arcade game I'm doing some custom programming for and its main data set is stored in 16 27c512's, but it's a 16 bit system so they're in pairs. So I'm wondering about the possibility of creating a small satellite board that would plug into the bottom pair and have two 28 pin sockets for two One ROMs. Then a header to break out the upper address pins where I'd just use jumper wires to connect to the 7 banks of upper ROMs. Then I'd just emulate 28c040's with the One ROMs and cat my ROM images together in the right order.
Are there any reasons why this wouldn't work? Any special considerations with wiring? This all assumes that the address and data bus lines are consistent across that ROM bank with nothing but the upper address lines being different, and I believe that to be the case. Which in my head means it's as simple as a board with nothing on it but wiring, but it's always at least a little more complex than that, right?
Obviously I'd rather buy 2 One ROMs than 16, but it's also about ease of programming, too (and this is just the dataset, I'll need a few more One ROMs for the rest of the board stack).
All reactions