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Joey Z

atari 400/800 U1MB interface board/64K upgrade interest check

atari 400/800 64K RAM board/U1MB interface checking interest  

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  1. 1. would you be interested in a 64K RAM upgrade board for the 400/800? This would also allow the installation of a U1MB into a 400/800

    • yes
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    • no
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I've been thinking a little, and I think it would be fairly easy to build a RAM board for the atari 400/800 which would occupy the first RAM slot, have a ribbon cable run out to the 74LS42 address decoder, and provide 64K of RAM and the XL OS to the board. I think there would NOT need to be many soldered modifications, maybe to add a hard reset (or just modify the OS to detect the 400/800 NMI style reset). I would do my best to include a way to enable and disable the upgrade, so you can return to 400/800 mode and have all 4 joystick ports available for use, etc. The main purpose for this upgrade would be to put a U1MB into a 400 or 800, and plug it into this board. The existence of an MMU socket, a 28 pin style OSROM socket, and all of the other necesary signals pinned out for the U1MB (with the exception of /HALT which would require a connection to the CPU board I believe) would make the installation all but plug and play since all 400/800's are socketed. The only non-plug and play bit would be the soldered connection to /HALT on the ANTIC, I believe. In addition to providing U1MB connections, this upgrade could be used standalone as a 64K upgrade, just use an OSROM (would be provided) and an MMU (would probably be present on the board as a CPLD) and it works by itself.

 

I was thinking I would do my best to keep the price below $50, though I suspect it'd be cheaper even (the concept itself isn't all that complex IMO, so I'd estimate $30 at the least). Of course, this is only checking interest, I'm not saying I will do this in quantity just yet, or that everything I said is even correct/that the concept is totally viable.

 

EDIT: also, I know that the incognito is basically U1MB + SIDE converted for the 800. I know there are subtle differences in the software, like the U1MB stuff using a different key in place of help on the incognito. To that effect, hopefully Candle will helpful in this regard, and allow me to make some small changes to the U1MB firmware image to allow easy use with this board, which would have to be flashed into the U1MB once installed. I know this seems a lot like incognito, but the difference is that it also supports the 400. That was my original plan, to make it for the 400, but there's no reason it couldn't work in an 800, so I might as well support it. I don't mean this to compete with incognito, I want to make that clear.

 

EDIT2: typo, there will NOT need to be many soldered modifications

 

EDIT3: 400/800 use 74LS42 as address decoder, not 74LS138.

Edited by Joey Z
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I would almost certainly buy one, unless a fourth run of Incognitos happens first. Possibly even if it does.

 

EDIT - If the price point really turns out to be that low, I would buy one. I already have an Incognito in one of my 800s, and I would love to make my second 800 XL-compatible. Or one of my 400s. Or both. I'm pretty much a guaranteed sale at $50 or less.

Edited by adam242

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Don't forget RD4 and RD5, the RAM deselect lines from the cart slots. They aren't on any RAM slot, though they can be decoded from the 2nd RAM slot's S4 and S5, but that's no help on a 400.

 

Also, the signal you need to control the 800's data buffers is only on the 3rd RAM slot and on the OS ROM board.

 

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Don't forget RD4 and RD5, the RAM deselect lines from the cart slots. They aren't on any RAM slot, though they can be decoded from the 2nd RAM slot's S4 and S5, but that's no help on a 400.

 

Also, the signal you need to control the 800's data buffers is only on the 3rd RAM slot and on the OS ROM board.

 

yes, I've been looking. I would need RD5 and RD4, or decode them from S4 and S5. on 400, two additional wires would be required for RD4 and RD5 no matter what.

 

I don't believe I need to control the data buffers. The personality module decodes that control based off of signals that will cause it to work just fine the way it is. The only thing that can't happen, is the OSROMs being on the bus. This is easily accomplished since I will be replacing the 74LS42 address decoder via ribbon cable to the board. I just need to make sure S7 doesn't come on, and S6 will go to the MMU IO select pin, which only turns on for the I/O address range, meaning the FPROM doesn't come on.

 

So the buffers will turn on for I/O, cartridge, or OSROM access (correct me if I'm wrong). The only thing I need to ensure is that the OSROMs aren't enabled on the bus ever, easily accomplished by tying S7 high in the 74LS42 socket, and asserting S6 only during an I/O access (also easily accomplished by connecting to the IO select line on the MMU).

 

I will also likely need the reset line to tap into, for ensuring proper initialization of my PORTB emulation (to avoid wires coming off the PIA), and figure out what I'll be doing with the soft reset line. I could add one more soldered connection, and support switching between soft reset and hard reset between XL and 400/800 mode.

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I would be interested, though honestly another run of Incognito boards would interest me more (assuming I have the funds when the time rolls around - if I've learned anything over the last 5 years it's not to take ANYTHING for granted with regard to money).

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I really don't know what to say here.... I have an Incognito, and love it. This seems like a good project, but not as good as Incognito. No offense. Having said that, If another Incognito was not available, I probably would buy this for another 800.

 

What we really need to complement the Incognito is a replacement CPU card that combines Rapidus (or XL14) with VBXE. That would be the "missing link" in the evolution of a super 800.

 

After that, a high speed parallel and serial card with full handshaking, which could use all available RAM card signals, and those of the Incognito PBI via a very short ribbon cable.

 

After that... We still have 2 slots left... The sky's the limit.

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I really don't know what to say here.... I have an Incognito, and love it. This seems like a good project, but not as good as Incognito. No offense. Having said that, If another Incognito was not available, I probably would buy this for another 800.

 

What we really need to complement the Incognito is a replacement CPU card that combines Rapidus (or XL14) with VBXE. That would be the "missing link" in the evolution of a super 800.

 

After that, a high speed parallel and serial card with full handshaking, which could use all available RAM card signals, and those of the Incognito PBI via a very short ribbon cable.

 

After that... We still have 2 slots left... The sky's the limit.

I know, I really do know, but I can't just copy candles U1MB and call it my own or something. The advantage that this would have is really that it fits in a 400. I could design my own 1MB upgrade, similar to the U1MB, completely independently, or I could just do this and make it an adapter for the U1MB. It takes less time, the only difference between this and the incognito is the SIDE. Incognito is literally U1MB + SIDE, that's pretty much it. Anyway, that's my thoughts on this.

 

I've also thought about making the various signals needed for PBI available as a header, at least the ones that the other RAM slots don't already have. This way, peripheral boards could be used in the other slots.

 

I guess the final question is this, do people want me to develop my own memory expansion board, similar to candles U1MB? this would take more time, likely not be as good or as featureful, at least at first, but I'd be developing it as open source hardware completely. The other option is the one I've put forth already, you plug a U1MB into a card, the card goes into the RAM slot, you get U1MB on your 400 or your 800.

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It's all good, do what you feel is best. I'm sure there are people out there who will need this upgrade. This would provide a nice way for 400 owners to upgrade.

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A Single Incognito-like Board to make the 400 XL compatible would be great although built-in CF is a bit impractical.

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Look at the bus buffer control circuit on the OS ROM board. S7 is not involved. You need to assert EXSEL to prevent the buffer from coliding with RAM data. Search for my previous posts about 800 RAM expansions.

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Look at the bus buffer control circuit on the OS ROM board. S7 is not involved. You need to assert EXSEL to prevent the buffer from coliding with RAM data. Search for my previous posts about 800 RAM expansions.

yeah, I thought about that just this morning of course... I was really hoping I wouldn't have to use slot3, I'd have rather kept that open for the upgrades that already go there.

 

However, upon further looking, this problem can be solved in fact, without additional soldering. You will pull Z102, and OR gate, and (possibly) place it into a socket on the upgrade board. You will connect a ribbon cable to this chip's socket. This chip handles R/W L and the RAM S4/S5 lines to RAM, and to the personality slot. When the atari is accessing an I/O address, the RAM S4 and S5 lines will remain unasserted by the upgrade board. In this case, the personality module will handle the control of the buffers properly, turning them on when accessing anything but GTIA/ANTIC registers, which are present before the buffers, on the CPU card. If accesses to the cartridge area are made, and RD4/5 are high (whichever is appropriate for the address range) then again everything happens as normal as the personality module will control the buffers properly. If RD4 or RD5 are low during an access to their respective address range, then either RAM S4 or S5 will be asserted and this will disable the buffers. If an access to the OSROM area is made, then RAM S4 or S5 will become asserted and again disable the buffers.

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That should work, and you'll have two ribbon cables to the motherboard.

 

IMO this would be too similar to Incognito. What would be more desirable for many 800 owners would be a solderless solution or even one that simply plugs into slots without opening the case. Between slots 0 and 1, you have A15, S0, S1, RS4, RS5, S6, S7, and A13 thru A0. That's enough to decode the entire address bus, get RD4 and RD5, and control the buffers. So a two-board set, with interconnecting cable, could do everything except 130XE-style ANTIC bank switching, and it would just plug right in. That I would buy.

 

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That should work, and you'll have two ribbon cables to the motherboard.

 

IMO this would be too similar to Incognito. What would be more desirable for many 800 owners would be a solderless solution or even one that simply plugs into slots without opening the case. Between slots 0 and 1, you have A15, S0, S1, RS4, RS5, S6, S7, and A13 thru A0. That's enough to decode the entire address bus, get RD4 and RD5, and control the buffers. So a two-board set, with interconnecting cable, could do everything except 130XE-style ANTIC bank switching, and it would just plug right in. That I would buy.

 

Being similar to the incognito was kind of the point, this is supposed to 1. provide a solution for 400 owners who want to upgrade their machine and 2. fill the gap in the market left by incognito since incognito isn't currently available.

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Just curious, those of you who said you would buy, how many of you would be buying to use as just a 64K upgrade, and how many of you would be buying to use with a U1MB? If many of you would buy to use it with U1MB, I'm considering just making it into a U1MB style upgrade. Perhaps I could offer a lower cost option using the same board, but less featureful.

 

If I am able to make the board support multiple configurations, the base model would include:

XL compatibility (64K SRAM upgrade)

socketed 64KB flashROM

This would be divided up into eight banks of 8K each. One would be used by a setup menu of sorts, at least two would be used for one 16K OS, and normally one would be used for BASIC. From there, you have 32K more space for additional OSes or random cart images (both 8K and 16K would be supported, maybe left cart emu too), or you could sacrifice BASIC to put one more 8K cart if you don't care about BASIC.

It may or may not include an RTC, this would also allow you to save a setup with non-default OS and non-default bootup cart. Of course, this adds some cost.

Lastly, a CPLD to handle all the decoding, with schematics available and a JTAG if you want to mess around ;)

This would require soldered connections on the 400 to RD4/5 and a ribbon to Z102 on the 800. On both, it would require a ribbon to replace the 74LS42, Z101 on the 800 I believe, and Z103 on the 400. Also, on both machines you need a connection to the RESET circuitry and the RESET *button* circuitry. Unfortunately, I can't find any way around this, even a modified OS would fail to reset if it were mapped out, so you really do need a way to hard reset in XL mode. I know they have little pin-grabber things that could make this solderless, but I'm also worried about the reliability of those connections. Lastly, you would still be able to disable the upgrade in software and return to normal 400/800 mode, in which case you will have 48K RAM, and your original 400/800 OS will be used (although I suppose if you wanted an alternate OS, you could use 16K of the ROM for that).

 

The 512KB/1MB model would (hopefully) include:

the base 64K SRAM

512KB/1MB extended SRAM (512K/1MB is your choice, if you want to save a bit of cash, all I do is leave a chip off and program a CPLD differently)

64KB socketed 'failover' flashROM - this kicks in if you screw up flashing the main ROM somehow on accident

(hopefully) 2MB soldered main flashROM (for all the carts/OSes you can fit) - again, one 8KB slot (at least) would be saved for a BIOS/setup program, and you'd need at least one 16KB OS, and there'd be a BASIC slot. On this advanced model, I'd do my best to support more than one banking scheme. I've been thinking about ways to do this, and I think I have some ideas, but we'd have to see how they turn out. You could leave this ROM off to save cash, but I don't think it's too expensive anyway. The reason it's not on the base model is because the CPLD pins to control it are a bit expensive.

an RTC of course, also for saving configuration data.

a bigger CPLD (because bigger is always better :-D)

full schematics and a JTAG for tinkerers of course

same requirements as the base version for installation, but you'd need to add to that a soldered connection to the /HALT line if you want to use programs that take advantage of separate ANTIC/CPU access for extended memory. Aside from that, no additional differences, unless we start adding more features not listed here....

 

Lastly, if anybody wants to plug a U1MB into their 400/800 still, that adapter board is not too complex and I could have it drawn up in a matter of weeks.... you'd still need the ribbon to the 74LS42, the ribbon to Z102 (or soldered RD4/5 connection on the 400), the reset circuitry connection, the reset button connection, and /HALT for separate ANTIC/CPU access. You may also need to reflash ROM image of the U1MB so that it works optimally with this setup, since the 400/800 is a bit different from the XL/XE. This may not be so easy to put back into 400/800 mode, but I'd certainly see if it's possible and do my best to incorporate at least a way to connect a switch or something.

 

So there you have it: which of the three are you really looking for in this hardware?

 

Also: slot-2/3 IDE/CF board isn't out of the question for the 800. It's a long shot to put this on the same board with the memory upgrade, since the dual flashROM and cartridge banking compatibility stuff I want to do would probably take up any extra real estate that would be left on the board.

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I'd be perfectly content with the base model. 64k and the ability to run XL software is really all I'm looking for.

Maybe the 512k version, if that would allow 130xe compatibility.

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I'd be perfectly content with the base model. 64k and the ability to run XL software is really all I'm looking for.

Maybe the 512k version, if that would allow 130xe compatibility.

yes, the 512K version would give you 130XE compatibility, there would certainly be a mode for it. The beauty about it is that I should be able to make the same board support both configurations, so if enough people want either the 64K base version, or the advanced version with additional 512K or 1MB extended, I just need to get one board made and the rest is just different CPLD programming and leaving off or including certain parts.

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I mainly want the 64k XL compatibility and ability to use different OS's. 130XL compatiblity would be nice, but it would depend on how much the price goes up. I would like to keep it under the $50 price point you targeted.

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Were you aware that Candle was at one point considering a modified version of Incognito for the 400. I don't know if this was cancelled or just delayed, the last post in the thread was over a year ago.

 

http://atariage.com/forums/topic/207429-atari-400-incognito-like-upgrade/?hl=+ultimate%20+400

yes, I am aware of that. I see no indication that he still plans on producing it, but candle has been a bit more active on the forum lately, so it's possible he'll chime in. Anyway, I'm going to do this whether there's interest or not, but if there's not enough interest, then I'll just be producing one only, for myself. My concept of 64K/576K/1088K versions, I think, sounds like a good idea to me, so I'll be *trying* to design for this. When I have stuff working, I'd be posting a new thread to kind of show it off, and also regauge interest again. This thread will be helping me decide what people really want in this upgrade.

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I think the base model would probably be enough for a majority of people, especially if it comes at a low cost. What sort of price difference is there between 64K and 1088K?

 

A device like this that would make the 400 more useful would be very nice for the 8-bit computer hobby. Plus the 400/800 models will probably outlive all of the other models. In fact, they would be the only models standing after an EMP.

 

Any chance of remapping the joystick ports 3 & 4 to some other locations when in XL mode?

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I think the base model would probably be enough for a majority of people, especially if it comes at a low cost. What sort of price difference is there between 64K and 1088K?

not sure yet

 

A device like this that would make the 400 more useful would be very nice for the 8-bit computer hobby. Plus the 400/800 models will probably outlive all of the other models. In fact, they would be the only models standing after an EMP.

If any are left standing, it'd have to be the 400/800, yes :)

 

Any chance of remapping the joystick ports 3 & 4 to some other locations when in XL mode?

Yes, should be no problem to do that.

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The extended ram looks like it can be had for $6 (a 1Mx8 chip, and cheaper than 2 512Kx8 chips, so there goes the 576K version most likely) and I think the 2MB flash ROM was something like $3-$5. Some additional glue logic will be needed for the 2MB flash ROM, maybe $3 for that. The bigger CPLD could make it $4-5 more. So if I had to estimate on the high side for price difference, I'd say no more than $25 more for 1088K over 64K.

 

Again, this is just an estimate though, when I have a design that I think will work, I will be able to get a better price estimate for the 64K and 1088K models.

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