gregallenwarner

What I have discovered from experience is that those little cheap composite to VGA converters that PeBo mentioned: Some work and some do not. I had purchased one of those exact same converters, and it suffered from the vertical banding. Then I searched eBay for another one, and although it was an identical form factor, it apparently had different electronics inside and it worked perfectly with the TI. Unfortunately, I can't look up which one it was from eBay because it was such a long time ago, and I've since ceased using it in favor of the F18A. However, my theory is that it indeed has something to do with the "interlaced" vs "progressive" nature of the color signal. From what I can tell from my research, true NTSC color spec requires the color carrier be 180 degrees out of phase with itself on each successive scan line. (This allows for the color signal to effectively "cancel itself out" on older black-and-white TV's without color filters, a throwback to the introduction of color era.) However, based on the appearance of the image coming from the TI, it doesn't appear to be alternating the color phase every scan line. Each scan line appears to be in phase with every other scan line. There are many methods to decode NTSC color, however, one of them: the "comb filter" presents a problem here. The comb filter works by storing each scan line in a buffer, and "subtracting" the next line from it, in order to extract the color information. If the color phase doesn't switch between scan lines, the comb filter subtracts all the color information right out of the image, and the result gets interpreted as luminance (brightness) information, resulting in the vertical banding. So my recommendation is to try purchasing another composite to VGA converter, preferably of a different brand name. They're not all the same, and what you're hoping for is to get lucky with one that doesn't use a comb filter, but rather some simpler form of color decoder. Like I said, I was able to successfully locate one, and they're cheap enough to try a couple of brands. All the theory above is purely a thought-experiment of mine, based on lots and lots of reading and research. I don't own an oscilloscope to test my theories, but I believe my reasoning is logical. Hope that helps somebody out.

8 ports?!?! I imagine it probably had to have some buffer chips to avoid hitting the TTL fanout limit. Did it require an external power supply to power up all those carts? Or can the TI cart slot source that much power?

What's intriguing to me is the multi-base mod for the cart expander, the schematics for which can be found on Thierry's (newly restored) site. I'd love to build one of those someday, and perhaps build one entirely from scratch so I can have even more carts pluged in, and all accessible through the TI's menu! Has anyone built the multi-base cart expander?

Great news! Thanks for the update, mizapf!

I was going to focus my efforts on creation of new pages that are needed. I figured I'd start with the Speech Synth since it's something I've been spending a lot of time with recently. Let me know if there's any specific needs for new pages, and I'll see what I can do. Thanks! Edit: Nevermind, I see there's already a speech page. It wasn't linked from some of the other pages, so I figured the page didn't exist. I guess I can go through and create links between pages wherever it's needed.

Sent my application to ninerpedia, mizapf. Took me a while to find the email confirmation message because it got sucked up in my spam folder.

I agree. His site has been my #1 resource ever since I discovered it, and he deserves the traffic if he plans to continue hosting it. I'll look into applying to ninerpedia.

I simply maintain everything I do as open source, across the board. That way, I don't have to deal with it.

I love the idea of a collective effort to maintain a wiki. I'm definitely game for being a regular contributor.

Anyone know how to get in touch with Thierry? I've got some web hosting and I could commit to long term hosting of a mirror, if he's ok with that.

Just an update to everybody who's wondering where I'm at with this project: I've gotten the revised boards in; I had to add a buffer chip between the PEB bus and the speech synth, to see if that would solve my issues with my first prototype. However, my forgetfulness bit me when I took a look through my inventory; I had spec'd out the chip to use way back when I did the redesign, but I realized I had failed to order any. Anyway, I got my parts on order, so I should be able to assemble the 2nd round of prototypes soon as they come in. I think I'm going to create a new official thread for this board whenever it comes time for the big run, to give everybody a chance to lock in their order, but I've got everyone's name written down who's expressed interest either on this thread or by PM, so I can be sure to make enough for everybody. The number is currently over 30 so far! I can't thank everybody enough for their interest in my project!

It's been my experience that HDX doesn't work well unless you're using a real serial port. The USB emulated serial ports tend to be dodgy. Don't know for certain if this is the case 100% of the time, but no USB to serial adapter has ever worked for me. If anyone else has had success using a USB to serial device, I'd be interested to know the model adapter you have.

Referred here from the Yahoo group. (Next node in linked list:) Found the Yahoo group via Google.

I don't wanna hijack this thread or anything, but when the time comes (and I feel ready to reveal them) I'll start a new thread.

In the past, I've considered what it would take to revamp the firehose connection, and I briefly visited wireless before realizing it would be a headache to implement and make sure the timings were exactly correct. My current idea is using a pair of MAX10 FPGA's, one on either side, sampling and serializing over LVDS with a shared clock to keep them synchronized. At minimum, it would require two twisted pairs (for full duplex), plus one more twisted pair for the clock signal. An ethernet cable would provide all the wiring needed, with one twisted pair left over. It's not a trivial project though. Getting reliable timing would be tricky. It'll be a long while before anybody can expect me to tackle a project like this, as I've lots of stuff lined up to do right after the speech adapter card is finished.

Modern "high brightness" LED's are gonna be glaring in comparison to the old-school LED's of the 80's and 90's. So if you are gonna have a mix of standard and high-brightness ones, be sure to stick a 1K or higher resistor on those high-brightness ones. I built a card solely for the purpose of testing CRU bits once, and I put an RGB LED on there, with each color hooked to a different CRU address. I wrote a program to cycle through the CRU bits, producing a rainbow of colors from my PEB. It's too bad I didn't take any video of it! I'll have to hook it back up one of these days and re-run the program so y'all can see it. It's pretty trippy.

Now can we get every permutation of combinations of chips from 2 to 7 out?

I've thought about an FPGA floppy controller, since I've been studying programmable logic as of late. However, what I'd expect in a product like this is full backward compatibility with the existing drive controllers, so that none of the software will need to be modified. What I am lacking is a fully documented description of those disk controller chips and their theories of operation. But if you could find something like that, theoretically, a disk controller could certainly be built in that manner.

The most effective way to produce a TI-99 replacement would be to program a system on a chip using an FPGA. Many other classic systems have been implemented on FPGA's, so there's no reason the same couldn't be done for the TI.

My guess is that one of the VRAM chips has gone bad. The standard fix for this these days is to install an F18A module. The side effect of this would be that you now get VGA output to boot!

SIMM's are dynamic RAM, or SDRAM (Synchronous Dynamic RAM) to be precise. They require some controller circuitry to dynamically refresh the cells. That would be a lot more complex of a circuit, since static RAM's can basically interface directly with the PEB Bus.

Ah, gotcha. Makes sense.

What's the key to those 74ABT series chips? Are those different from standard 74LS or 74HCT series?

That Y-adapter cable that I linked above.

There was a website selling exactly that: a Y-adapter ribbon cable to connect 2 PEB's. I believe this was the site: http://www.iec-usa.com/cgi-bin/iec/05MCOlderTI.html though I'm not sure if they still sell that cable. With a flex interface card in each peb, there's no reason why you can't have 2 peb's on one ti bus. Just be sure no two cards conflict on either address decoding or cru addresses. Edit: they do still carry that cable: http://www.iec-usa.com/cgi-bin/iec/L1173