Need Help-Percom RFD Board

[+Nezgar]

1 hour ago, MrFish said:

Actually, I have a third dump, that matches the CRC of Moonlight_Mile's AT-88. I have no idea where I got it from (maybe Pigwa). It's labeled as "AT-88 Add-On Drive". Do the Add-On's carry their own ROM?

OK, that's a start. With phaeron's comments I would also lean toward Moonlight_Mile's dump since it burns less "extra cycles."

 

Percom add-on drives do not contain controllers, and hence do not have any additional ROM/firmware. They are just bone stock standard PC compatible  mechs in a case with a power supply and a card edge connector to connect with a ribbon cable to the drive with the controller. (up to 3 add on drives) The lower cost for additional drives was part of Percom's marketing pitch...

http://www.vintagecomputing.com/wp-content/images/retroscan/percom_atari_large.jpg

[+MrFish]

15 minutes ago, Nezgar said:

Percom add-on drives do not contain controllers, and hence do not have any additional ROM/firmware. They are just bone stock standard PC compatible  mechs in a case with a power supply and a card edge connector to connect with a ribbon cable to the drive with the controller. (up to 3 add on drives) The lower cost for additional drives was part of Percom's marketing pitch...

http://www.vintagecomputing.com/wp-content/images/retroscan/percom_atari_large.jpg

That's exactly why I hadn't mentioned it until now; because I was assuming they didn't carry their own ROM. I had figured someone just mistakenly renamed the ROM that Moonlight_Mile posted; and until I can find more reason to believe it's a unique dump, I'm going to continue assuming it's a duplicate.

 

[+Nezgar]

I re-dumped my VER 1.2 ROM while determining the process to use an Atari EPROM cart PCB for the job, saving out the cartridge memory area using DOS 2.5.

 

This process consists of placing the 2KB 2716 EPROM into an Atari 16KB EPROM cart PCB C015783. With the 2716 EPROM in the right socket, the 2KB shows up at $A000-A7FF. With the EPROM in the left socket, it shows up at $B000 to $B7FF.

 

Anyhow, using this process, my resulting CRC is 2372FAE6, with $FD at location $05CA, matching moonlight_mile's dump. The EPROM must just be marginal, maybe the TL866 programmer is reading it "too fast" compared to the real drive or the Atari computer.

 

So I'll probably delete the bad dump from my prior post to prevent it's spread.

 

 

[moonlight_mile]

I actually got another rom programmer. A GQ-4X. I can’t remember but I may have used that one to dump the AT-88 rom. I can’t remember. I got that so I could program the 2716 I had because the eeproms I ordered got canceled with all the Covid-19 stuff going on in China.

Not sure if it matters but I figured I would let you know.

[+Nezgar]

I'm curious about 2816 EEPROMS... would be handy for quick erase to test... Looks like the TL866 directly supports ATMEL AT28C16 which are readily available from eBay... Hah, well, now that I've looked, I couldn't help but pull trigger on 2 from here. https://www.ebay.com/itm/183371366623 We'll see if that gets cancelled too Looking at UV EPROM 2716's, they all seem to require 21V for programming, so will only work in a TL866 Rev 1, not the Rev 2, so I'm good there with my V1...

 

But for now, its nice that 2732 EPROM's are a drop-in replacement in the PERCOM as well (using half of the ROM). I programmed your V1.2 into a fresh 2732 with the original 2KB content repeated twice since I don't know how the PERCOM keeps the highest address line, and it works fine. With more testing, I could figure out if it only needs the code in the higher or lower half of the 2732's 4KB ROM space. It will have to be in both if the highest address line floats.

[moonlight_mile]

Well, I have just about got all my Percoms back up and in running shape. However of the big rfd-s2 it is missing the board cover plate. Does anyone have a spare they would sell? Or better yet does anyone know of someone/somewhere I can have one made or 3D printed? I would prefer a metal one but I don’t have a brake to bend the metal and don’t think any of my local hardware stores will do that for me. So I would love to have one (or 3) 3D printed. Again I don’t have the equipment or the skill to do this myself.

Any suggestions?

I did see someone was selling a tandon 100-1a with it attached on ebay. But 1 it was too overpriced and two I have enough full height drives floating around. Lol.

[tschak909]

So functionally, which PERCOM is better? The AT-88 or the RFD?

 

-Thom

[moonlight_mile]

So functionally, which PERCOM is better? The AT-88 or the RFD?
 
-Thom

Well, before a year or two ago I never had an At-88. In the 80s I only had the rfd for my bbs.

I find them really both functionally the same. The At-88 may be a little quicker to recognize a disk and start booting. But that could be because it is a single density drive. Otherwise, I would say they are pretty much the same.

I haven’t pulled the At-88 out in quite some time so maybe there are some differences that I don’t remember. Will have to drag her out and play around with it.

[moonlight_mile]

Found a pic of my original Percom and Drives.  RFD Board and Mitsubishi Quads.

 

 

[erichenneke]

The AT88-S1PD genuine schematic from percom shows 2732 with 11 address lines. (although only 2KB is used/repeated...)
 
The RAM is 2x 2114's in both schematics, 1Kx4 SRAM's for 1KB RAM total. They seem common enough on ebay.

Do you have a scan of the AT88-S1PD schematics or any other diagrams of AT88-S1PD? I find a lot of RFD documentation but little on the AT88 from a technical or electrical perspective.

Thanks!
Eric

Sent from my E6533 using Tapatalk