Jump to content

Texas Instruments Dimension 4

Recommended Posts

  • 2 weeks later...

I had a chance to disassemble the Dimension 4 and make some pictures. It is different from the parts I have, but the difference is not as great as I initially suspected. Like mine, the motherboard has very few components on it--including the video modulator. There is a switch on the left side of the console to select between channels 3 and 4.


Like mine, the CPU and most of the logic is on a daughter board. I thought mine placed this board above the motherboard, but looking at this one, I may have been wrong (or this is just another difference). This daughter board is placed below the motherboard.


The cartridge port connectors are the same in both versions I have. The attachment is quite different to the ones we use in production consoles though.


The power supply is different too--it uses a 10-pin connector to attach to the motherboard. The exit from the console is just a cable from the power supply, so I suspect this was not how it would have looked when in production, as there was a space there for the external power supply connector we use now.


This leads to another difference between the two part sets. The Dimension 4 has a speaker jack for sound. My parts set has a small board that replaces the internal power supply with one of the volume slide switches and connects to an internal speaker. All power comes into the console in the form of the required DC voltages.


The parts themselves are also instructive. The chips in the Dimension 4 look to be made on or before the 44th week of 1978, whereas the parts in my loose parts set have chips made as late as the 52nd week of 1978, so these two board sets were probably made about 8 weeks apart, near the end of 1978.


For those of you looking for pictures, download the attached ZIP file.  :)  Have much fun with these, Fabrice!

Dimension 4.zip

Edited by Ksarul
  • Like 14
  • Thanks 4
Link to comment
Share on other sites

6 hours ago, fabrice montupet said:

I come back from a few days business trip and I just discovered your Dimension 4 pictures!  So Great!!

Since this evening, I will study them. I'm so happy ?

I am happy to have been able to give you this happiness, Fabrice! It was a very careful disassembly, as I wasn

t sure where all of the screws and solder points were hidden. Luckily, it was just a few screws and a bunch of pins that slid through the boards to establish contact--no solder removal required.

  • Like 2
Link to comment
Share on other sites

  • 3 years later...


Interesting to see this thread resurrected - not only with the Dimension 4 photos (amazing!) but also the Foundation CP/M scans globeron posted on the first page.


The Foundation literature is weirdly barefaced about its unfairness, at least regarding their use of benchmarks to contrast the 9900 and the Z80a. The second benchmark, a block move of 1000 bytes from one location to another, exemplifies this.


The Z80a accomplishes this in a fast 5.25 ms, using a single dedicated block move instruction. That’s a cool feature, but one cherry picked to give the Z80a maximum advantage over the 9900. Foundation calculates the 9900 will require a miserable 29+ ms to accomplish the same block move. But that's with everything arranged in the worst possible light. 


Here are some numbers I obtained. They speak for themselves.


99/4a with 16-bit RAM in console:


           500 16-bit MOVs:  8.5 ms. 

           1000  MOVBs:  15.5 ms.  


Stock 99/4a (emulated with Classic99), registers in scratchpad:


          500 16-bit MOVs: 12.7 ms.

          1000 MOVBs: 23.5 ms


Stock 99/4a  (emulated with Classic99) registers in 8-bit RAM:


          500 16-bit MOVs: 16.5 ms (essentially 1/2 as fast as 16-bit RAM)

          1000 MOVBs: 31.5 ms.


Related, kinda:


The January 1983 BYTE article reports the Z80 executing 10 iterations of the Sieve in assembly in 6.8 seconds. My 16-bit 99/4a does the same 6.4 seconds, a stock console in ~10 seconds (registers in scratchpad).  


The fastest Z80 running interpreted BASIC under CP/M executed 10 iterations of the Sieve in 1476 seconds. (In a later review the TRS Model II did so in 1440 seconds.) My 16-bit console running Cortex BASIC entirely out of 16-bit RAM executes the Sieve in 1313 seconds. Running out of the FinalGrom (with some of the interpreter therefore executing from 8-bit RAM) it executes in 1781 seconds. (I don't have numbers for a stock console).


The fastest Z80 Forth execution of the Sieve is reported at 75.9 seconds, while FIG Forth executes in 84 seconds. Wycove Forth 3 (descended from FIG Forth) executes the Sieve in 92 seconds given 16-bit RAM. It would probably clock at about 130 seconds on a stock console. 




Edited by Reciprocating Bill
  • Like 2
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...