Piotr D. Kaczorowski

As I remember @flashjazzcat updated AtariWriter for VBXE native 80 column driver.

Well, actually, I'm not sure what the problem was in your case. NCR is best for Rapidus, but I know that people also run it with other Sally processors. In my opinion, the issue might be with the power supply stability or incorrect wiring. In the next two days, I'm going to finish setting up an Atari 800XL with Rapidus, PokeyMax, Sophia 2, SRAM, and SIDE 3.1. I usually work with the Atari XE or 600XL, so this will be a new venture for me.

Well... I use NCR CPUs. There was a rumor that they might even go up to 4Mhz. They might not, but they heat up less. It seems that they run more stable than Mexico.

If everything works, it's boring in the meantime... motherboard has been prepared for tomorrow

I will try to improve the stability of Rapidus-Ultimate 1MB-SIDE3.1 on 800XL on Sunday and Monday. We'll see if there are any surprises...

@mytek, In my computer, the O2/Fixer is used to supply the twin BO2 to Ultimate 1MB. The remaining issues are resolved differently. Antic is located in the VBXE adapter and in general, it's difficult to supply the twin BO2 signal there. GTIA doesn't need to be connected to the O2/Fixer because: 1. I have removed Freddie (VBXE+SRAM and input to the board at 3.5Mhz), I have swapped Pokey for PokeyMax, and PIA has been replaced with the new WDC NMOS PIA. The whole system runs very stably with SIDE 3.1 even in Rapidus 20Mhz mode.

@mytek, And according to my experiment, there was still a shortage of 4xTTL. As I said, after replacing PIA, Pokey, GTIA, and removing Freddie (installation with VBXE 3.5Mhz + SRAM, without Freddie), everything started to work. The laboratory version of O2/Fixer was built on two 74F08 ICs. It should be noted that this computer had all the extensions, including Rapidus.

@Peri Noid, The first four AND gates are the same as in the 74xx08 circuit - according to the schematic. So it depends on the Atari computer where BO2 enters the mainboard. For example, in Atari XE, the original BO2 enters the mainboard from pin #3. I would like to point out that I deliberately call the additional BO2 signals "twin" and not "clone" or "copy". After connecting the O2 pin to the soldering point in the center, all BO2 signals are generated simultaneously, with the same propagation time. The only difference is the so-called twin BO2 OUT_1, which does not have an additional capacitor (has CMOS characteristics) and is dedicated to Ultimate 1MB.

@mytek, Ok. I wouldn't want anyone to think that I'm advertising O2/Fixer because I don't financially benefit from it. I understand the issue with 74F08 and that it's a first aid solution. That's indeed the case. However, for more complex issues, O2/Fixer helps. Another topic is that most people connect the Ultimate 1MB to the O2 signal - for example, to the SRAM 64K V2/V3/V4 board. So, this is a simplification, because U1MB, like everything else, should be connected to the BO2 signal, and here O2/Fixer provides the most appropriate signal with CMOS characteristics (more rectangular) than NMOS. Essentially, my intention was for the price of O2/Fixer to be set in such a way that it would essentially be an addition to other extensions, which wouldn't significantly increase costs. 74F = FAST => F.airchild A.dvanced S.chottky T.TL and is up to 125Mhz I believe that not increasing the parasitic capacity is a technological element that makes the "F" work so fast. An additional story is that when starting experiments, I accidentally connected an oscilloscope with a probe set to a 1x multiplier and connected it to pin #39 of Sally. SIDE 3.1 stopped working. Thus, the capacity of O2/BO2 and its impact on other devices can be easily checked. I know that a few years ago, other fixers were developed in place of 74LS08, which were designed by Simius. From what I know, they were based on PLL and signal reproduction. However, I also know that this system did not help with all the problems. I hope that the ability to separate between systems and feed them cloned twin signals will improve stability for most users. I conducted tests on about 15 Atari boards at home. Lotharek did on a few at his place. The project, in its conceptual phase, was consulted with Simius, XAngel (Polish Atari hardware hacker), and AcidMaker (SIO2SD / Medusa Upscaler). Ultimately, it was finalized and is now being produced by Lotharek, which gives it a scale of availability.

@mytek There are many solutions, just like in IT. It turned out the way it did and it works. It provides additional possibilities. I think the project is so simple that there's no need to consider additional improvements. My earlier concept was to create a "Sally-to-Sally" adapter. It would be similar to the "6502-to-Sally" adapter, but the inserted processor would still be the 6502C Sally. The main task of the board would be to disconnect pin #39 and introduce its own O2 signal there, generated similarly to the Atari 400/800 (or the Sweet16 65C816 project) externally from the Phi0 signal using a 1-gate. This would result in a strong O2 signal being fed to the board. Of course, tests would need to be conducted again. From what I've seen, Lotharek plans to release a board that will contain such a circuit along with the WDC65C02S processor in the QFP version. It's possible that he will also release such boards with the 65C816 processor, as well as versions with SRAM included." I think the "F" series didn't change the conditions due to speed or signal strength, but rather due to the lack of introducing additional parasitic capacitance - which is why it could also operate quickly. The "F" series operates up to 125MHz according to the specifications.

@mytek, 74LS08 (or 74HCT08) has 4 AND gates. O2/Fixer has 8 AND gates: 4 AND gates that works like 74xx08 and extra 4 AND gates, that are configured as "twin BO2 signals" in set of OUT_1 - CMOS like BO2 and OUT_2...OUT_4 - NMOS like BO2. If you intend to use the twin BO2 signals, they should be connected to the top of the Ultimate 1MB system or to the bent legs of the Atari circuits so that they are not shorted with the main board. If someone asks about the latter, the answer is: that was my idea and it has been proven in the lab that it works. I had the opportunity to test the so-called reverse system degradation (or gradual system stability improvement) on a machine with SRAM, U1MB, VBXE, Rapidus + SIDE3.1. The board that had the above components had a built-in 74LS08 circuit. SIDE 3.1 completely froze the computer upon startup. After replacing the 74LS08 with 74F08, the computer started with SIDE 3.1 in 6502 mode, but did not start in 65C816 mode. After replacing the 74F08 with the O2/Fixer prototype (containing 74F08 and a second 74F08 generating four twin BO2 signals) and connecting the PIA to the first twin BO2 signal, the computer started in 65C816 mode, but SIDE3.1 froze the computer upon entering the loader via Ultimate 1MB. After switching the Pokey to the next twin BO2, the computer worked in the SIDE 3.1 loader, but the cartridge had trouble handling the SD card (it was still disturbed). After connecting the GTIA to the next twin BO2, the computer worked correctly in 65C816 mode with SIDE3.1 reading SD cards. A similar effect can be achieved by replacing the PIA, Pokey, and GTIA circuits. The PIA can be replaced with the WDC PIA NMOS (W65C21N), which has limited clock line capacity expansion due to newer technology. The same is true when changing Pokey to PokeyMax and GTIA to Sophia 2. In the case of O2/Fixer, technology was also used that significantly reduces the capacity introduced on the clock line. Additionally, through additional capacitors, the NMOS characteristic has been preserved.

@Beeblebrox, If it works well, there's no need to complicate things further. If it doesn't work, you need to successively bend the legs and connect them to OUT_2... OUT_4 until it works.

So what did you actually do? Did you connect the signals from O2/Fixer to the Atari ICs (Pokey/PIA/GTIA/Antic) without bending those O2/BO2 legs, right?

Because DRAMs are not for reinstallation... they should be removed just once

@Beeblebrox, Well... Correct. The project is based on my idea and laboratory. Besides, my name is on the board. However, I decided not to take any remuneration (in Poland, the board costs 29 PLN, which is 6.6 USD / 6.3 EUR / 5.4 GBP) because it's a very small project, and I wanted all the other extensions to work together (Ultimate 1MB, VBXE, Rapidus, SIDE 3.1). For now, I personally earn from the SAVO boards. You can see how the instructions for them are written: http://ftp.pigwa.net/stuff/projects/SAVO/ My colleague, the producer, and my colleague, the UK distributor, quickly wrote the instructions for O2/Fixer. I will correct it when I have some free time.

Interesting... This weekend I will be disassembling and reassembling the Atari 800XL with U1MB and Rapidus. Inside, there's a PokeyMax and Sophia 2. Unfortunately, SIDE 3 doesn't work. We'll see how it goes this time.

@Beeblebrox, The original O2/Fixer prototype was built using two 74F08N chips. As you can see, the Pokey, PIA, and GTIA are connected via twin BO2 signals provided by the second 74F08. The current O2/Fixer is constructed with eight 1-gate chips and capacitors that emulate NMOS characteristics. The first step is to replace the 74LS08/74HCT08 with the O2/Fixer. If you have the Ultimate 1MB, the second step is to connect the U1MB O2 pin to the O2/Fixer U1MB twin BO2 (OUT_1 - you can check that there is no capacitor on the other side of the board). The third step is to rewire the Atari circuits to the twin BO2 signals (OUT_2 ... OUT_3). When I have a moment, I'll check the instructions on the RetroLemon website. I consulted on this description, but it was done very quickly, so there might be something that still needs to be added. To be honest, it's still better than the first version of this description

Absolutely not. I simply insert the chip into the socket. Then I bend one leg, which corresponds to the O2(BO2) signal, and connect that leg with a Kynar wire to the O2/Fixer.

@woj, 1. O2/Fixer should fix that problem. O2/Fixer is made of 1-gates and capacitors that simulate the NMOS characteristic with the smallest possible increase in parasitic capacitance on the BO2 clock line. 2. The answer to the question of whether SRAM affects the O2/BO2 characteristic is YES. This is due to several factors. Firstly, on the SRAM board, the O2 clock signal is used to control the SRAM memory, where it passes through a 1-gate and is supported by a pull-up resistor (on different boards these values range from 2.2k to 10k). The 6502 processor specification speaks of an O2 load with a maximum of one TTL connection and a maximum capacitance of 135pF (information from a book I have). Therefore, it should be remembered that in the case of the SRAM board, the O2 signal reaches the 1-gate on the SRAM board and to the 74LS08 or 74HCT08 gate, which are factory-installed in Atari XL/XE. In the case of NMOS technology, disturbances at low signal throw are subject to interference, and further on, this disturbance can translate into powering another system that receives the signal and transferring the disturbance further. This disturbance can also be frequency filtering or frequency filter generation (this can interfere with the operation of SIDE3/3.1). Using O2/Fixer makes it resistant to disturbance transfer and capacitance loading of the BO2 line. Additionally, you have at your disposal four more twin BO2 signals, one of which has a characteristic well seen by Ultimate 1MB. In the case of a large number of internal extensions and stability issues, it is also worth connecting the BO2 signals of subsequent Atari systems from the top - not through the mainboard, but directly to the twin signals. This will cause the separation of BO2 between systems, as well as the reduction of parasitic capacitance. In the end, it's worth noting that the wires between subsequent extensions should be as short as possible. Long and twisted wires act as antennas and generate as well as receive interference. As for SRAM, I always use it in my installations because, after all, it is a single memory in new technology that also does not require refreshing, so it generates significantly fewer disturbances. On XE boards with VBXE, you can completely get rid of the Freddie system, which also reduces interference. So there are more pros than cons.

For my own convenience, and from observing what people do (as seen on YouTube videos), I decided that an interesting solution would be to create a special RESET key handler, which sets the options as above. Such settings could be introduced in the next version of Action! in the preferences file. Then they should be taken into account when starting the editor and after returning from monitor mode to the editor.

Actually ESP32 S3R2 and S3R8 both have internal quad and octal SPI PSRAM. I wonder how fast it could be @240Mhz.

Okay. Thank you. I'll keep that in mind during further searches.

A8PicoCart V2 @electrotrains, ASELECT should be connected to A of 74LV139 (2-to-4 decoder/demultiplexer) and Y0, Y1 of 74LV139 should be connected to OE of two 74LV541A (3-state octal buffer/line driver or other octal bus transceiver, maybe with latches ) that handle A0-A7 and A8.. Outputs of both bus transceivers should be connected to GP5-GP12. GP0..GP3 should be connected to 64Mbit (8MB) PSRAM that could handle any of cartridge for Atari. What do you think about that?

ADVANCED CODE SEGMENT MANAGEMENT

TCO Recursion - TAIL CALL OPTIMIZATION