bbking67 Posted February 14, 2014 Share Posted February 14, 2014 One of the web sites for the SIO2Sd has some instructions to remove a resitor and add two capacitors to improve SIO speed and reliability. Is this a reliable mod? Seems easy to do and claims to increase speeds tremendously (I'm assuming using the right drivers). http://sio2sd.gucio.pl/wiki/HighSpeed_en "In most cases SIO2SD can work with speed up to 127kb/s (hsindex = 0) without major hardware modifications. The only important thing is to add 4k7 ohm resistor (if you do not have one already) between SIO DATAOUT and +5V (pin 1 and 5 of SIO connector). It should be enough, but more advanced users should remove also at least two capacitors from Atari. Capacitors to be removed connect DATAOUT and DATAIN with ground. Those are small, 100nF capacitors (looks like resistors). In 800XL, 65XE and 130XE computers they have numbers C77 and C78. To show the difference please look below at oscillograms - with and without those capacitors." Quote Link to comment Share on other sites More sharing options...
Kyle22 Posted February 14, 2014 Share Posted February 14, 2014 I don't have SIO2SD, but I do have a SIO FIFO, and the removal of those capacitors made all the difference in the world. I feel that those capacitors should be removed on all Ataris doing any kind of highspeed SIO. Quote Link to comment Share on other sites More sharing options...
Kyle22 Posted February 14, 2014 Share Posted February 14, 2014 One of the web sites for the SIO2Sd has some instructions to remove a resitor and add two capacitors to improve SIO speed and reliability. I missed that the first time. You REMOVE the two capacitors, do NOT ADD any. Can't say for sure about the resistor. Quote Link to comment Share on other sites More sharing options...
bbking67 Posted February 14, 2014 Author Share Posted February 14, 2014 (edited) I missed that the first time. You REMOVE the two capacitors, do NOT ADD any. Can't say for sure about the resistor. Oops I reversed that... add the resistor remove the caps i meant. What is the purpose of adding the 4K7 resistor between data and gnd? Edited February 14, 2014 by bbking67 Quote Link to comment Share on other sites More sharing options...
Roydea6 Posted February 15, 2014 Share Posted February 15, 2014 Oops I reversed that... add the resistor remove the caps i meant. What is the purpose of adding the 4K7 resistor between data and gnd? Re Read the info about the resistor. ++++++ Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted February 15, 2014 Share Posted February 15, 2014 Re Read the info about the resistor. ++++++ Why? I think he wants to understand the theory behind it. Quote Link to comment Share on other sites More sharing options...
bbking67 Posted February 15, 2014 Author Share Posted February 15, 2014 Re Read the info about the resistor. ++++++ I'm not sure I follow? The instructions say to add a resistor... I guess there might be one there already??? Quote Link to comment Share on other sites More sharing options...
Rybags Posted February 15, 2014 Share Posted February 15, 2014 Resistor between DATAOUT / +5V - I would think that should be to help improve rise time, ie slope of SIO output when going from 0 to 1. I did some stuff with PIA outputs that relied on precise high-speed switching when testing video output (used PIA as trigger). Early on I realised it was pointless relying on the 0 -> 1 transition as it just took so long and was inconsistent. High-speed SIO it's probably the same case. 1->0 transitions tend to be very fast but not necessarily the case the other way around. Quote Link to comment Share on other sites More sharing options...
Marius Posted February 15, 2014 Share Posted February 15, 2014 On xe I removed all those sio caps is that a bad decision? Quote Link to comment Share on other sites More sharing options...
Rybags Posted February 15, 2014 Share Posted February 15, 2014 Shouldn't matter I'd think - usually Data In & Out are the only ones where the fast/precise switching matters. Clock runs at the data rate but most peripherals don't use it. Quote Link to comment Share on other sites More sharing options...
npturton Posted February 15, 2014 Share Posted February 15, 2014 Resistor between DATAOUT / +5V - I would think that should be to help improve rise time, ie slope of SIO output when going from 0 to 1. I did some stuff with PIA outputs that relied on precise high-speed switching when testing video output (used PIA as trigger). Early on I realised it was pointless relying on the 0 -> 1 transition as it just took so long and was inconsistent. High-speed SIO it's probably the same case. 1->0 transitions tend to be very fast but not necessarily the case the other way around. Correct the resistor is known as a pull up resistor and is used to improve the rise time Removal of the caps (or resizing) remove the rounding effect on the edges of the square wave data pulse train, thus faster switching can occur without crosstalk Quote Link to comment Share on other sites More sharing options...
atari8warez Posted February 16, 2014 Share Posted February 16, 2014 (edited) All my Ataris have caps intact and I have no issues with high-speed SIO with an SIO2PC, I can run divisor 0 no problem with Hias's patch and the U1MB or IDE+2 high-speed OSes (which I believe are basically the same thing as the Hias patched Atari OS). I wonder if removing the caps will actually make any difference in real throughput on a given baudrate!? Edited February 16, 2014 by atari8warez Quote Link to comment Share on other sites More sharing options...
Rybags Posted February 16, 2014 Share Posted February 16, 2014 Just listening to the IO noise will usually indicate how healthy it is, if it's having high success rate it'll be a smooth, consistent train of beeps. Wonder if anyone has done an in-depth SIO health benchmark - ie something that lists how many command retries, how many data frames retries etc. Quote Link to comment Share on other sites More sharing options...
Roydea6 Posted February 16, 2014 Share Posted February 16, 2014 (edited) One of the web sites for the SIO2Sd has some instructions to remove a resitor and add two capacitors to improve SIO speed and reliability. Is this a reliable mod? Seems easy to do and claims to increase speeds tremendously (I'm assuming using the right drivers). http://sio2sd.gucio.pl/wiki/HighSpeed_en "In most cases SIO2SD can work with speed up to 127kb/s (hsindex = 0) without major hardware modifications. The only important thing is to add 4k7 ohm resistor (if you do not have one already) between SIO DATAOUT and +5V (pin 1 and 5 of SIO connector). It should be enough, but more advanced users should remove also at least two capacitors from Atari. Capacitors to be removed connect DATAOUT and DATAIN with ground. Those are small, 100nF capacitors (looks like resistors). In 800XL, 65XE and 130XE computers they have numbers C77 and C78. To show the difference please look below at oscillograms - with and without those capacitors." If it is +5V and SIO DATAOUT then the website should read (pin 10 and 5 of SIO connector. I took my Atari apart last night and put a resistor between pin 1 and pin 5 and I got no response at all from the SIO2PC and AspeQT. I had to take the resistor out and re read my book and realized that pin 1 is not the +5 V pin. reliable who knows. Someone just wrote above to use data and gnd. Edited February 16, 2014 by rdea6 Quote Link to comment Share on other sites More sharing options...
lemiel Posted February 27, 2014 Share Posted February 27, 2014 Between pins 1 and 5 on SIO2SD board, not in Atari SIO plug. 1 Quote Link to comment Share on other sites More sharing options...
re-atari Posted February 28, 2014 Share Posted February 28, 2014 (edited) One of the web sites for the SIO2Sd has some instructions to remove a resitor and add two capacitors to improve SIO speed and reliability. Is this a reliable mod? Seems easy to do and claims to increase speeds tremendously (I'm assuming using the right drivers). It was already known back in the 80's that SIO speed could be made more reliable if you removed the pulldown caps from the SIO datalines. Compyshop advised Speedy 1050 users strongly to remove 2 caps from the 1050 PCB, these serve the same purpose as the ones you refer to. This mod was essential in order to make use of the highest SIO speed supported by the Speedy. re-atari Edited February 28, 2014 by re-atari Quote Link to comment Share on other sites More sharing options...
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