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About ClausB

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    space and rocket history, astronomy, photography, math, computer programming, physics, digital electronics, Atari, aviation, sports cars, Star Trek, Star Wars, Doctor Who, my family, to name a few

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  1. Turns out the 800 was unstable even with a good 16K board, and so the 48K board was likely working all along. Happy accident though because the redesign has more solid CAS timing, based on Phi2 instead of a couple gate delays. Reseating boards and chips in the 800 fixed it, and it and the 48K RAM have run flawlessly for 36 hours.
  2. Yes, the keystroke programming was cumbersome but it gave me a mindset which made it easy to learn assembly language later.
  3. Sold my 56 in college to buy a 59. Later got another 56 off eBay. Good sites: http://www.rskey.org/CMS/index.php/exhibit-hall/97 http://www.datamath.org/Album_Sci.htm
  4. My first computer was a TI SR-56 in 1976. Did any of you have one before your TI-99?
  5. And yes, that's what I did on Thanksgiving morning.
  6. Well, the prototype became unstable, probably the marginal CAS timing. Revised it to use Phi2 like the later Atari boards. Working so far. More testing ahead...
  7. But if you do solder to the socket pins, remove the IC from the socket first to prevent heating.
  8. Here is the simplified version which uses the original 74LS10 at Z501, so fewer wires and lifted pins. Built and tested. Look for complete modification instructions in an upcoming issue of pro(c) ATARI magazine!
  9. We've ignored the power draw of the TTL chips on the RAM boards, which is about 0.3 W. So one 48K board will save another 0.5 W or so over 3 16K boards. Total savings, rounded up, is about 3 W.
  10. Nope, that's max power, not typical power, and it's at the chip's max cycle rate. At the Atari's rate of 1.8 MHz, power is considerably less. Also, depending on whether the Mosaic design keeps 24 chips in standby when 8 are active, consumption can be even lower. See analysis on 48K here:
  11. I did that simplistic power analysis a while ago and pasted it above. Here's a more thorough one: MOSTEK 4116 data sheet (https://console5.com/techwiki/images/8/85/MK4116.pdf) shows 462 mW max at max cycle rate of 2.7 MHz. Can't use that because the Atari's cycle rate is 1.8 MHz and not every chip is active every cycle. Page 2 shows standby 12V current as 1.5 mA. Fig. 2 shows an equation for max active 12V current, giving 27 mA at 1.8 MHz. Say each 16K bank is active at most 1/3 of the time on average (because there are 3 banks) during non-refresh cycles. All banks are active during refresh, which the Atari does 8% of the time. So each bank is active 39% of the time. Each chip then averages 0.39*27 + 0.61*1.5 = 11.5 mA. At 12V that's 137 mW per chip, plus less than 1 mW at +5V and -5V, plus bus load. 24 chips then draw 3.3 W max. Bus load cancels in the comparison with the 4164, and the difference is only 2.3 W!
  12. The -5V bias supply is very low current. The +5V supply is just for the data out buffer, so it depends on the data bus load. The main chip power comes from the +12V supply, and it is very dependent on access frequency. My datasheet has graphs from which I estimated 24 mA at 1.8 MHz. What is the access frequency in your datasheets?
  13. I haven't built and tested the simpler alternate design yet, though it's equivalent logic, so it should work. Yes, it was likely my DIY 256K upgrade for the 800XL. RAMbo and Wizztronics were commercial versions of it.
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