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Post by eslapion on Sept 3, 2021 4:32:56 GMT
That's really interesting. Does that mean half the read/writes fail in fast mode? That would be a problem. Also, can I just mod the NeoRam to remove the clock and fix it? I don't know the answer to your 1st question. Since NeoRAM uses static RAM too, I don't know why the 1MHz clock line is used. AFAIK, it isn't necessary. I assume it's a legacy of the people creating the first NeoRAM from GeoRAM and noticing the output is disabled depending on the value of the clock signal. Maybe they didn't notice this was only necessary for refresh cycles.
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Post by eslapion on Aug 30, 2021 20:11:04 GMT
I have built 5 NeoRam boards, the ram chips I used were all SMT but the logic was DIL. I didn't know about the clock/phi0 thing. Can you explain what this means for the 128 in Fast mode? There is a ramdisk tool for the 128mode and if that didn't work in fast mode I would be sad. If you look at the schematic of NeoRAM/Remix you can see phi2 is connected to pin 6 of both 74_138 decoders and this makes the expansion visible during the CPU part of the cycle on a C64. The other half being culled was necessary for refresh cycles as the original GeoRAM used dynamic RAM. On a C64, this was no problem as this is the same half used by the VIC-II to access the normal DRAM for display. On a C128, in slow mode, the CPU uses half the cycles and the VIC-IIe uses the other half, pretty much like on a standard C64. In fast mode the 40 column display must be disabled as the CPU uses both halves of the cycles and the VIC-IIe can no longer access DRAM for display. Ergo, a standard GeoRAM and NeoRAM (and NeoRAM remix) are unavailable when Phi0/Phi2 is low. Mine is available all the time as there are no refresh cycles. The clock line isn't even connected to the CPLD on my model because there is no need to check which half it presently is. In fact, the static RAM is so much faster that there would be no problem if the CPU was running at 10 MHz.
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Post by eslapion on Aug 23, 2021 23:25:22 GMT
How is this different from the existing open-source "NeoRam" board? NeoRAM uses the phi0 clock signal and that limits it to 1MHz access rate. NeoRAM doesn't use surface mount parts and is quite large. NeoRAM does not exist in 4MB. The product I offer will not require you to build your own board. AFAIK, NeoRAM is GNU which means it can't be sold and you must get the files for it, get your PCB fabricated and build it yourself. This requires a fair amount of technical know how.
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Post by eslapion on Aug 20, 2021 0:55:04 GMT
Hi, Although I do not have a need for a GeoRam since I am using a 16MB RAMLink I just wanted to say that $80 for the 4MB version seems to be a very reasonable price. gglabs.us/node/2056 first sold its model at around $120 / $140. Granted there are some differences in the memory used that could explain the price differential. I am not sure about the battery back - up, but If I could I would suggest maybe a coin battery RTC. I don't have any schematic for an RTC so I can't offer one. Point me in the right direction and I'll see what I can do. AFAIK, the RTC in CMD drives is integrated with the firmware of these drives so files have a date automatically generated. GeoRAM is just a lot of RAM so including an RTC with no system smart enough to make any use of it would be rather pointless. From your link: "GRAM/4D is a 4MB geoRAM compatible cartridge based on a two 4Mx4 DRAM devices." This means this device requires refresh cycles and therefore should be incompatible with the 2MHz mode of the C128.
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Post by eslapion on Aug 19, 2021 21:51:04 GMT
Hi People!
I have a GeoRAM clone that uses static RAM that is almost ready. The prototype is working. This design uses static RAM and is not dependent on a clock signal for refresh and multiplexing timing so unlike some other types IT IS FULLY COMPATIBLE WITH THE FAST MODE OF THE C128.
The design can support up to 4 MegaBytes but of course, the larger the amount provided, the higher the price tag.
My question: How much would you be willing to pay for 2MB or 4MB GeoRAM and would a battery backup have any usefulness ?
The greater the functionality, the higher the price tag.
Right now, a 2MB version without battery backup should sell for about 45$US. A 4MB version without battery backup should be around 80$US.
People have indicated they would prefer a battery backup in the features. So be it.
CleoRAM is available! You can order now!
57$US (50 Euros) for the 2MB version, 90$US (77 Euros) for the 4MB version. Shipping to the US is 8$US, shipping to Europe is 8 Euros.
This expansion uses HALF THE POWER OF AN ORIGINAL FASTLOAD CARTRIDGE!! LARGER POWER SUPPLY NOT REQUIRED!
Photos of the product have been posted on Melon64. You must provide a CR2032 lithium battery. It is estimated the battery will require replacing once every 3 years.
No case is provided: The board shape is exactly the same as those of game cartridges made by Commodore in the 1980s so you can either 3D print your own case with publicly available files or buy a standard case from many different sources.
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Post by eslapion on Aug 8, 2021 6:02:30 GMT
Perifractic posted a video on YouTube in which he cleans up and repairs a very dirty C128 and he shows the 3 products I make for that machine. These are: - Saruman-128 which replaces all 16 4164 DRAM ICs. - Saruman-VDC which increases the VDC RAM from 16k to 64k - TOLB which replaces the 8701 clock generator See here: youtu.be/GiXNEf_NOak
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Post by eslapion on Jun 18, 2021 18:28:18 GMT
Forgive my impudence but I see a couple of technical issues with your design.
For starter, since the output of the C128 RGBi port is digital, how come you need to have potentiometers ? These will require adjusting and I don't know exactly what people will use as reference to do that.
IMHO, you just need to use a high speed logic buffer such as 74AHCT245 which is compatible with the TTL levels of Commodore computers to restore the signal to full 0-5V rail to rail levels and then use a network of 1% tolerance resistors to convert the signals to analog values.
For another, there is absolutely no need to have a 12V input then 5V regulator on your board as you can just take the 5Vdc from the datassette port and perhaps clean it up with an LC filter.
Also, the dot clock on the 80 column output of the C128 is at 16MHz so using the finest surface mount parts to get a good quality video signal is important. IMHO, you should use TSSOP ICs and 0603 or 0402 discreet parts.
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Post by eslapion on May 30, 2021 5:07:25 GMT
Still available from me and offered in the U.K. by Retroleum.
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Post by eslapion on May 8, 2021 19:01:20 GMT
The version for the C64c is presently available at the same price. I must confess that I have thoroughly failed to grasp, well, SOMETHING about this. How does a RAM expansion for the 80-column chip in a C128 have any applicability to a C64c? I get the parallel use case involving the C16 / C116 / etc. Like the C128's VDC subsystem, that family of machines also has a 64K address space that's only populated by 16K. The C64c, not so much. Please un-bewilder-ate my poor brain! It's because you took this sentence totally out of its context. Let me explain. I also make another product called Saruman-TED and another one called Saruman-64. Saruman-TED will increase the RAM of a C16 from 16k to 64k. Saruman-64 replaces the DRAM ICs of a C64 or C64c completely but from an electronics point of view, they are extremely similar to Saruman-VDC. When you use Saruman-TED, you can completely remove the DRAM of a C16 if you want to. If you use Saruman-VDC, you can remove the 2 DRAM ICs reserved for the VDC if you want to. Saruman-64 takes the place of the DRAM (of a C64 or C64c) so you have to remove them. Yes, there is such a thing as an adapter to use Saruman-VDC to replace the RAM of a C64c but it's not very practical as Saruman-64 is less expensive. Also, there are people who have good experience with soldering who used a Saruman-64 to take the place of the VDC DRAM and got 64k for their VDC this way instead of using a Saruman-VDC - it's less expensive but it's more difficult.
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Post by eslapion on May 2, 2021 6:28:10 GMT
New lower price! 15$ each (13.50 Euros)
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