Recent content by na103

there is something strange that I don't understand.:unsure: IC E5, E6, E11 and E17 are present in the part list. However, they are not present in the schematic and a note on the layout sheet says that they are spare. I checked in the pictures of N.BROWN, E17 is not there but the others are...

the motherboards rev A and B, vt100 are already present in the bisavers archive. PC100B memory extension is in my repo github and also here somewhere in the forum. of the PSU I think there is only reverse engineering by Tony Duell. so it's all interesting. obviously nothing is urgent in these...

Hi Guenter, once again you save the day. thank you, thank you so much for these schematics. now I have a few nights to spend awake working on the 8087 adapter. send picture of everything you find! Regards Nicola

from what I've seen when a 100B memory is installed via the 8087 adapter on the Rainbow 100A, MEM PRES remains high. this means that the logic does not detect the presence of the extension memory and I think that even the BIOS memory set-up settings in 100A become irrelevant. at this point all...

however this does not matter for RAMbow. I can eliminate E29 and manage the addressing with a GAL logic and a jumper to set when RAMbow is installed on 100A or 100B. The E27 multiplexer is also useless as it is only needed if you intend to use the 100A's memory card on the 100B. There's probably...

it seems that before the multiplexer E27 the address lines (A16 - A19) were probably modified to overcome the memory gap problem by going from rev A to rev B. the address lines are reversed after the latch E32 and then passed through a full adder E29. I'm not yet clear how the latter changes the...

I don't want to create false expectations, I'm working on it. at the moment I have modified the board with nine 1Mbit DRAM and removed all the bank switch logic no longer necessary. as you can see there is room for 8088 and other logic. thanks to N.Brown's images I'm trying to understand how...

Is my opinion that RAMbow could be an all-in-one board consisting of the memory card + 8087 adapter. in the article it says that it was sold fully populated with nine one-megabit chips. This creates space on board to place the CPU socket and any other logic. At the moment I'm busy with other...

Hi, I'm joining this interesting brainstorming by adding some information about the DM74S287N PROM. in my remake it was replaced with a more modern GAL. to do this I had to reconstruct the truth table based on the specifications of the manual. the memory banks of the option ram are activated or...

I have no experience with greaseweazle, take a look here https://forum.vcfed.org/index.php?threads/a-few-decmate-ii-questions.1238538/page-2

You can't format a generic floppy disk unless it has been low-level formatted first. You can't do low level formatting from Rainbow. they were sold by DEC ready-made one solution is to restore an original disk image of a disk (from the PC with a 1.2MB drive) with teledisk and then format it from...

Hi Emanuele, have you tried reading an original DEC Rainbow floppy disk? the new RX50 floppies are preformatted at a low level and it is normal that generic ones cannot be formatted. It is however possible to restore a CPM disk image (TD0) using a PC and teledisk. later you can format this with...

Hi, take a look here https://www.a1k.org/forum/index.php?threads/71482/page-2#post-1463215

A lot cool and useful to use an AI from my IBM 5150 !

I bought it now on itch.io, I'm playing it and it looks very good game