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J.Ivy

console speedup mod

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http://www.mainbyte.com/ti99/speedup/speedup.html

 

So I found this article online, showing how to use dual crystals and a 2-way switch, to increase your ti speed up to 20%. I figured it would be a fun evening mod. So here it is.

 

Here you can see where the crystal was removed (the black and orange wire) and wires attached. They run through the board to the simple circuit. The speed "standard" or "fast" are determined by the knife switch, which side its connected to. This speedup wont work with every program, so you will have to switch it back to standard for some.

 

n15dll.jpg

 

xg9rwy.jpg

Edited by J.Ivy
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I had this along with many other switches installed in my system.

 

Load Interrupt switch

Cartridge reset button

CPU Idle switch

Dual Crystal toggle turbo switch

CPU reset button

Cartridge power off switch, so I could replace a cartridge and the system would assume it was same cart. (As long as not running cart programs at that time.)

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I had this along with many other switches installed in my system.

 

Load Interrupt switch

Cartridge reset button

CPU Idle switch

Dual Crystal toggle turbo switch

CPU reset button

Cartridge power off switch, so I could replace a cartridge and the system would assume it was same cart. (As long as not running cart programs at that time.)

I am curious, what were the use cases for the CPU idle switch? Was it a cool off companion to the turbo?

 

Has anyone ever reported CPU failure after running the turbo crystal?

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Installing 16 bit wide memory all over increases the speed by about 110%, compared to running code with everything in 8-bit wide expansion box RAM. Without changing the clock frequency. But it's more work, of course.

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I am curious, what were the use cases for the CPU idle switch? Was it a cool off companion to the turbo?

 

Has anyone ever reported CPU failure after running the turbo crystal?

Not the CPU but my anecdotal experiences point to the 9901 not liking it (lost 3 during the time I ran it.) The data sheet specifies a minimum clock of 300ns. At 3.58 mhz I believe the period is 279 ns (14.318 crystal.)

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J.Ivy, on 19 Apr 2016 - 02:56 AM, said:

So I found this article online, showing how to use dual crystals and a 2-way switch, to increase your ti speed up to 20%. I figured it would be a fun evening mod. So here it is.

 

Here you can see where the crystal was removed (the black and orange wire) and wires attached. They run through the board to the simple circuit. The speed "standard" or "fast" are determined by the knife switch, which side its connected to. This speedup wont work with every program, so you will have to switch it back to standard for some.

 

 

It's a Franken-system! Throw the switch, Igor, we need more speed!

 

So TI spent hours and thousands of $'s designing the PCB, and all the courses and text books say to keep your signal paths short and neat, and you go and connect two crystals via 2 feet of cable and a knife switch, and it still works. ;-) ;-)

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Sometimes the short paths are as much for RF signal suppression as anything else. An oscillator and a two foot antenna? I wonder... ;)

Just add this and work on your TI and watch tv also. s-l1600.jpg

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I am curious, what were the use cases for the CPU idle switch? Was it a cool off companion to the turbo?

 

Has anyone ever reported CPU failure after running the turbo crystal?

Well the IDLE CPU switch allowed me to freeze things without problems. Like a game could be frozen while I went to eat dinner.

(Never use it while talking to Hard Drives or Disk Drives)

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That's what I was thinking, Stuart! That's not supposed to work!

That is why a buddy put a Relay switch above the CPU and my switch just turned on/off the relay for the Crystals. It was a short path.

Relay was powered off the converter input.

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I ran this mod for awhile (non-switchable, just a straight crystal swap, for the same reasons others are expressing concern over upthread).

 

The benefit didn't outweigh the drawbacks. RS232 card needed a new ROM to handle the faster timing, tape programs were unreadable unless decoded and reencoded at a different frequency, plus reading about the dead 9901s and possible floppy drive timing issues caused me to revert. I put in the 16-bit RAM expansion to make up for the loss of speed.

 

Which reminds me: my joystick port works only with certain games (Parsec, for example) but not others (mostly Atarisoft). The joystick pair is an Amiga (TI model), and all keys on the keyboard work. Is it possible that I slightly damaged the 9901 by overclocking it and it is expressing that via intermittent joystick port issues, or would I be seeing total failure and keyboard issues as well.

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That's what I was thinking, Stuart! That's not supposed to work!

I've successfully run AVRs with a 20MHz crystal dangling from 8 inch wires. More works than you would expect! ;)

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Hello guys,

 

Not knowing where else to attach following I'm sticking an idea of mine to this thread: How is about exchanging the 3MHz version CPU TMS9900NL with the 4MHz version TMS9900NL-40 (plastic dip) or TMS9900JDL-40 (ceramic dip) to speed up the TI 99 4a? Has anybody of you already tried to realize this idea? I undertook a research via www on this topic, but didn't find anything. Does anyone of you know, if the internal electronic structures of these two versions of the CPU are probably built up slightly different (e.g. the circuit pathes have different widths despite having been produced using the same technology called NMOS)? If you can swap the two versions of this CPU, can you also overclock the 4MHz version CPU? If you must also change other ICs of the TI in order to exchange the two versions of CPU, then which other ICs have you got to replace?

 

 

Best Regards,

Edited by MueThor

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Increasing the speed of the crystal negatively affects RS232 transfers. The baud rates are based on the clock value in the console ROMs. Thus, not only would you need a new RS232 RON but also a replacement for the console ROMs. Otherwise, some of the baud rates will work and others won't.

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Hello guys,

 

Not knowing where else to attach following I'm sticking an idea of mine to this thread: How is about exchanging the 3MHz version CPU TMS9900NL with the 4MHz version TMS9900NL-40 (plastic dip) or TMS9900JDL-40 (ceramic dip) to speed up the TI 99 4a? Has anybody of you already tried to realize this idea? I undertook a research via www on this topic, but didn't find anything. Does anyone of you know, if the internal electronic structures of these two versions of the CPU are probably built up slightly different (e.g. the circuit pathes have different widths despite having been produced using the same technology called NMOS)? If you can swap the two versions of this CPU, can you also overclock the 4MHz version CPU? If you must also change other ICs of the TI in order to exchange the two versions of CPU, then which other ICs have you got to replace?

 

 

Best Regards,

 

Any time the timing and control logic is modified, the chances for unintended ripple effects increases. One effect of overclocking is the CPU load increases, which tends to make it (and any of the more dense chips like the 9901) run a little hotter. Heat, (followed by ESD) is the greatest threat to monolithic integrated circuits. The ceramic-bodied 9900's (and 9901's) dissipate heat more efficiently, and added socketing (another nice mod when experimenting) allows slightly better airflow due to the increased gap between the bottom of the IC and PCB. Where space allows, a heat sink can be added. The peripherals were designed with the DATA and ADDRESS buses running at a pre-determined speed. CRU logic speed is another factor. If you want to fool around with different timing mods to the motherboard, I recommend installing sockets to make swapping out logic chips easier. This gives the added ability to bend single pins outward to isolate signal paths.

 

I'm not trying to discourage over-clocking or system design changes, I think some of the home-brew ideas that are presented here are interesting. TI may not have been very perceptive where marketing is concerned, but their design work --when translated to production hardware, is hard to beat. Open up and compare any competing home computer from the early 80's and you'll find TI's design, materials, and workmanship are second to none. Commodore used a paper flap with an exterior metal foil for RFI suppression. TI used two clamshells of solid metal screwed together and metal clamps! Not only was the home computer more expensive to produce in terms of materials and labor, but it was built to last. Etch spacing, ground plane area, signal and power routing to avoid interference are all considerations when building a high-quality device. Factor in margin with components and you end up with a robust design that can last decades.

 

The first rule of modifying anything is: Do No Harm. Making something work, and making it work right are two completely different things. (Read that twice, it's a mantra worth committing to memory.)

 

When I left TI, I thought I was a pretty good solderer. I'd fixed thousands of boards, removing chips and making etch repairs. In my next job, (as an Electronic Integrated Systems Mechanic for the gov't) I was required to attend a one-week solder class. Thinking this would be a colossal waste of time, it took all of thirty minutes during the first day of class to realize just how little I knew in terms of high-reliability workmanship! We had to re-certify every year.

 

Several years later, I attended a five-week Micro-Miniature Repair course, (simply abbreviated "2M") and of the many courses I've attended during my career, that was the toughest. I was the only civilian (the rest were military) in the class. On the first day, the Lead Instructor proclaimed, "The majority of you will fail this course. Do not be discouraged. It is not meant for everybody. You can return in a year to try again." Again, the techniques I learned in that class were light-years beyond the certification I arrived with. Only two of us passed, and were invited back for the Advanced Course - after one year. (It was only two weeks long and much easier.)

 

When I left the gov't for a new challenge in the private sector, it involved building Flight-level (as in spacecraft) hardware. The skills I acquired paid off-big time. Close-up examination of spacecraft wiring is not only robust -it's just plain sexy. In a wiring bundle, the wires maintain their position relative to one another for the entire length of the run, with no crossing, and plenty of subtle bends for strain relief during vibe testing prior to launch. Fun stuff, and quite a leap from slapping wires together at TI.

 

The NASA-level workmanship classes we had to certify to solder were a vacation for me. 2M specs were so much harder. Since then, I've become certified to teach (and re-certify) soldering classes to the techs where I work now. It's a small part of the job, but definitely the most rewarding -especially if they've never been trained before. I'm still in contact with some of the "old" guys who taught me thirty years ago, and have since thanked them for helping to get me headed in the right direction. Now I'm one of them, so I've come full circle, with the responsibility to pass on what I've learned (occasionally through spectacular mistakes!)

 

If any of you have workmanship questions regarding modifying your boards or terminating wires to components or switches, don't hesitate to drop me a line and I'll try to offer up some constructive tips if needed.

 

CC

Edited by CC Clarke
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I actually had a lot of fun in the NASA standard soldering class I had to attend at Goodfellow. . .especially as the requirement to take it was a surprise. I arrived there for another pair of classes and was told that the NASA soldering course was a requirement to attend the other courses, but since I was going to be the only student for both of my scheduled courses, they'd compress all three of of them into the time scheduled for my original classes. . .the one-on-one training I received there was priceless. :)

Edited by Ksarul
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Hello all,

 

Oh come on you guys, pinch me :-D :P. Tell me now that you are still or were TI employees :party:. But then, with so much expertise here, it should be possible to return to the topic of this thread and answer my questions posed earlier and repeated again here :grin:: How is about exchanging the 3MHz version CPU TMS9900NL with the 4MHz version TMS9900NL-40 (plastic dip) or TMS9900JDL-40 (ceramic dip) to speed up the TI 99 4a? Has anybody of you already tried to realize this idea? I undertook a research via www on this topic, but didn't find anything. Does anyone of you know, if the internal electronic structures of these two versions of the CPU are probably built up slightly different (e.g. the circuit pathes have different widths despite having been produced using the same technology called NMOS)? If you can swap the two versions of this CPU, can you also overclock the 4MHz version CPU? If you must also change other ICs of the TI in order to exchange the two versions of CPU, then which other ICs have you got to replace?

 

 

Regards

Edited by MueThor
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You will almost certainly have to use a 4MHz-rated version of the 9901 when you swap out the 9900, and as CC Clarke and Atrax27407 already mentioned, timing is going to be an issue with a lot of software. Geneve users had similar issues when running stuff made for the /4A at full Geneve speed. Sometimes things worked well, sometimes sprites did crazy things, and sometimes a program wouldn't work well at all. Timing will cause issues. So long as you have the capability to switch between standard speed, 4MHz speed, and overclocked 4MHz speed, you should be able to keep things running fine. PEB cards don't have issues with the higher speeds--as Geneve owners (and 99/8 owners with Armadillo Interfaces) can attest--although the RS-232 card will do strange things because the BAUD rate tables won't be right. I may have to read out the DSR that I have for the 99/8-modified RS-232 card that I have and compare it to the standard DSR, as it is using a DSR designed for the /8 (the card is otherwise identical to a standard RS-232 card).

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