17 replies to this topic

[OLD CS1]

I picked up an untested cartridge and it turns out not to work. It hangs just after asking for the player's name. I cleaned up the contacts and tried in a different console to the same results.

Popped open the cartridge and found a smorgasbord of chips, including a very big ROM chip and two MCM2114P20 4k-bit RAM chips. I suspect the RAM could be bad.

I found a place that has 2114P45s in stock, but I recall from my old 8-bit days that the "20" and "45" indicate the speed of the chip. In the case of the TI-99/4A, will going from 200ns to 450ns make a difference in a cartridge if I decided to replace them?

[matthew180]

Those are 1024x4-bit SRAM chips, which is why there are two of them, i.e. to make a 1Kx8-bit memory. I have an datasheet for an NTE2114 that is 300ns, and a Intersil MWS5114 with 3 speed grades:

MWS5114-1 (250ns)
MWS5114-2 (200ns)
MWS5114-3 (160ns)

So maybe look around for those alternates. I'm not sure what the read access time is in the cartridge, but 450ns is getting pretty long.

Edit:
JameCo (http://jameco.com) has the 2114 200ns for $2.49ea.

Edited by matthew180, Thu Dec 1, 2011 12:58 PM.

[OLD CS1]

Nice find, thanks. I forgot about JameCo; for some reason I just checked Mouser then started browsing around. I also found what looks like a bad solder job on a leg of one of the RAM chips, so I'm going to spend some time re-flowing all of them.

I will probably pick up a couple of those 2114s, if only to have on-hand. I am not convinced that is the problem with the cart, but it does seem plausible.

[matthew180]

You can also get those chips from coinop / arcade shops, since a lot of boards used small (and some large) amounts of RAM back then. However, the two places I found were out of stock. I also checked Mouser, but the only "modern" 1Kx4 chip I could find was a Cypress part that is obsolete. However, if you want to do some rerouting, you can get 32Kx8 20ns SRAMs easy enough. That could replace both 2114s, but you would have to mod the pin connections.

[OLD CS1]

I am not partial to the idea of "wasting" memory, but that would be an idea. I would make an adapter board to host the 32k x 8 chip so as to avoid at rat's nest of wires. Though I would like to come up with real 2114s to keep the cart as intact as possible.

I am was pretty certain that no arcade shops existed around here, but every so often I see at least a truck-worth of coin-op cabinets at the dump. Unfortunately we are not allowed to rummage at our dump (I actually got a couple of good spare cell phones a long time ago.) I guess it is time to pull out the yellow pages and have a gander. For that matter, there are a number of old hacks at the flea market that might actually have a drawer full of ICs for me to rummage through. Too bad I do not know any hams around here; they are great for old computers and electronics which, somehow, defy the universe and stay working even through decades of abuse or mishandling.

I am hoping that reflowing will fix this. I just do not have the motivation right now to replace chips

[Stuart]

For the record, I read that anything with an access time of less than 490ns should be OK for a 3 MHz 9900 with no wait states. So the 450's should be fine.

The 2114 comes under a number of different names ... TMM314APLs are the same and are pretty widely available on the likes of eBay.

Stuart.

[jchase1970]

http://www.amazon.co...0/dp/B001HFB43O
AMAZON has them list $6.25. might be a bit high???

[Willsy]

I'll be very interested to see a youtube vid of this game if you get it going. I'm interested to see how sophisticated it is - since it needs 1K of ram and all that.

I'd also like to know more about the architecture of the chip - how does it map the 1K (cru, writes to ROM etc) and where does it map the memory. Enquiring minds want to know! Is there any discrete chips (74's etc) on the board. Can you upload a piccy of the board?

[sometimes99er]

[Willsy]

Interesting... I'm surprised it needs more than the 224 bytes of ram that would be available in the console...

[OLD CS1]

Thanks to all the hardware hacks who posted information here. Sometimes' video makes me really wanna get this going.

Willsy, I will put up a few pics of the board this weekend. Yes, there are a few discretes on the board; it looks pretty complex. My guess is that it uses at least part of the RAM for the interface with the MBX unit, which I do not have.

[OLD CS1]

Did this with my scanner while the batteries for my good camera recharge. Figure it might get you started

Attached Files

•  meteor shower.jpg   397.17K   14 downloads

[acadiel]

Yep, those are the MBX Cartridges. To date, they aren't emulated in any program (save PC99), and they were a challenge to get dumps from (you tried to dump them, you inadvertently bank switched the thing). Thanks to SNUG, I have dumps of all but one.

The HSGPL and Gramulator are the only two TI devices that can run the MBX ROM images.

[acadiel]

Here's a zip file with the actual MBX ROMs, as well as assembly header files, etc. You won't find these anywhere else.

I know there's one missing from here, but can't recall which one...

Attached Files

•  mbx.zip   193.21K   7 downloads

[Willsy]

Thanks VERY much for sharing these Do you know which bank switch method is used?

[RXB]

The MBX Carts just used a TI like banking system. One cartridge lower 4K at >6000 to >6FFF and cartridge upper 4 banks of 4K at >7000 to >7FFF

This is almost exactly how the TI XB Cartridge works with 1 lower 4K bank and two upper 4K banks.

[retroclouds]

Some more pictures can be found in this thread

[OLD CS1]

My contribution.

Attached Files

•  IMG_2810.JPG   1.67MB   13 downloads
•  IMG_2811.JPG   1.85MB   12 downloads