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Infocom Hitchhikers Guide & nanopeb


palmheads
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Hi gang

 

Was trying to get the classic infocom adventure "Hitchhikers Guide to the Galaxy" working on my TI & nanopeb the other night.

 

See here for getting the Infocom adventures

http://atariage.com/forums/topic/94628-pc-to-ti994a-interface/page-4?do=findComment&comment=1986803

 

I downloaded "Infocom CF7.zip"

 

In JS99'er with XB 2.7 added as a module, I can add the "HITCHHIKER.dsk" to DSK1, boot up into extended basic, and have the Hitchhikers Guide menu pop up instantly. Great! From there I can pick the non 80 column version, press a key to load the 2nd disk, and the game works perfectly.

 

On my real TI with nanopeb, (using the xdt tools), I can get the "HITCHHIKER.dsk" added to my CF card (as DSK10) , then I can make sure the DSK is on DSK1 for the nanopeb by issuing the:

CALL MOUNT (1,10)

Sure enough, with XB 2.7 module loaded into my real TI, and with "HITCHHIKER.dsk" as DSK1 on the CF card for my nanopeb, I can boot into Editor/Assembler. Sure enough, it tries to boot the Hitchhikers Guide menu. However "most" of the time I get a basic error popping up saying "Error line 280" with a text too long error. Sure enough when I list line 280, it has some garbled text.

 

I say "most" of the time, as from a cold initial start after having not tried for a few weeks, turning on my TI it actually booted & got the Hitchhikers Guide menu and I was able to play the game. However subsequent tries I always get the error on line 280.

 

Can anyone with a nanopeb/CF7 replicate?

 

cheers

Daryn

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If you have the non f18a version of the nano, that's your issue. It causes random issues with the F18a due to the nano initilalizing vdp ram before the f18a is ready.. When you boot your TI it should say nanopeb Vsomething in the middle of the rainbow bar screen..

 

Greg,

Apparently I have the F18A version of the nano, according to the start screen. What does this mean exactly? I have the F18 mod kit and it involves replacing the TMS9918A on the motherboard. What does the F18 nano accomplish exactly?

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If you have the non f18a version of the nano, that's your issue. It causes random issues with the F18a due to the nano initilalizing vdp ram before the f18a is ready.. When you boot your TI it should say nanopeb Vsomething in the middle of the rainbow bar screen..

 

Yup, mine has the nanopeb v18 on the TI home screen. Weird how removing the speech synth seems to have solved the issue.

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Greg,

Apparently I have the F18A version of the nano, according to the start screen. What does this mean exactly? I have the F18 mod kit and it involves replacing the TMS9918A on the motherboard. What does the F18 nano accomplish exactly?

 

It was a timing issue between the nanoPEB and the F18A.

 

...lee

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Yup, mine has the nanopeb v18 on the TI home screen. Weird how removing the speech synth seems to have solved the issue.

 

I'm not sure what might be going on here, unless it is a connection problem, because I think the only pin available at the side port that is not passed through the Speech Synthesizer is +5V.

 

...lee

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Greg,

Apparently I have the F18A version of the nano, according to the start screen. What does this mean exactly? I have the F18 mod kit and it involves replacing the TMS9918A on the motherboard. What does the F18 nano accomplish exactly?

 

It waits a few miliseconds during bootup to allow the f18a to finish it's startup routine before setting up the nanopeb's buffers in vdp.

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Yup, mine has the nanopeb v18 on the TI home screen. Weird how removing the speech synth seems to have solved the issue.

 

I had read errors all the time with my nanoPEB until I removed the speech synth. The same speech synth is working fine with a regular PEB.

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I had read errors all the time with my nanoPEB until I removed the speech synth. The same speech synth is working fine with a regular PEB.

 

It's probably important to note that the speech synthesizer does not adhere to the TI design guide by buffering the address and data lines. Aside from dirty contacts between the speech synthesizer and the nanoPEB, you could also be running into a fanout problem. To wit, there are too many chips connected to the expansion bus and the signal is being degraded to borderline uselessness.

 

TI tended to overengineer things, but I think the dictum to use 244/245s to buffer those lines on every single thing connected to the side expansion port was a good idea. That guarantees that whatever device you plug into the expansion port will not load down the bus.

 

Normally replacing the standard 74LS24x buffer chips with a 74ACT24x will solve the problem -- rail-to-rail logic levels, reduced power consumption, and typically can drive ten times the number of devices on the bus. This is the tack taken in the "flex-cable tune-up" modification, although the original author used a logic family (HCT) that gave only marginal benefits over the original LS.

 

Looking at the console schematic, the bus signals coming out of the console are buffered by a pair of 74LS367 and a 74LS245. Although the 245 is available in ACT, the 367s are available only in HCT. It's always worthwhile to replace LS with ACT, but replacing LS with HCT isn't always a net win when you're going for additional fanout capacity. You will, however, get rail-to-rail with HCT which could help.

 

Edit: when I say "rail-to-rail", I mean that emitted logic 1 is very very close to +5VDC and logic 0 is very very close to 0VDC. With CMOS families (denoted by the "C" in the part number), you get this behavior. With traditional TTL families (denoted by a lack of "C" in the part number), emitted logic 1 is +3.5VDC (or so) and up, and emitted logic 0 is +1.3VDC (or so) and below. Every device that is plugged into the line, be it CMOS or TTL, will drop the voltage of the signal available to other devices by a certain amount ,depending on the consuming device's needs and the fanout {basically the amount of current} supplied by the emitting device. The general rule of thumb when designing address/data buses is to keep the signalling as close to rail-to-rail as possible and the fanout as high as possible.

 

The problems reported in this thread sound very much like they're caused by a buildup of oxidation/crud on the contacts on the speech synthesizer, but it could also be caused by overloading the bus which would need chip replacement to fix correctly.

 

Lastly, it could also be crappy solder joints on the nanoPEB. The later units were notorious for their poor construction -- perhaps you have one of them (I did). Fifteen minutes with a soldering iron, fresh solder, and a bit of wick, and you're good to go.

Edited by ckoba
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Interesting - so it could be the speech synth's (dirty) contacts.

 

Am just pleased to have a fully functioning nanoPeb.

 

It could be a number of things, dirty contacts being a prime suspect, but there are so many random problem reports with the nanoPEB that it's hard to tell.

 

I am curious how many gates in that Xilinx FPGA are sitting on the address/data buses, and if the FPGA bothers to buffer them. The LS chips in the console are supposed to be able to drive twenty LS gates per; supposedly they can drive an infinite number of CMOS gates, but I wonder if there's something going on in that Xilinx that loads down the bus to the extent that the TI will only operate reliably when only the nanoPEB is attached.

 

*shrug* You're good go to for now, though, so my curiosity is merely academic at this point.

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