Hi, Dear people, I do apologise if my attitude came across that "I'm gonna rip this apart for spares if I can't fix it", or if I came across aggressive. It was not my intent to antagonise, nor was it my desire to induce sympathy. Unfortunately the written word often lacks the character and nuances of speech. So, let me rephrase.... I purchased an old Intel MDS Series-4, specificaly for spare parts for my operating MDS Series4. The advertised unit has a memory error, but the rest of it checks out fine. My preference is to try and fix the broken unit. However, should my main unit have a problem I can always use the busted one to be a donor. If anyone knows exactly what chip 0000:8001 refers to (when doing a RAM test), then I will replace the offending component and have this unit fully operational. Which will make me a happy chappy. When I went to collect the unit the seller also said I could have the 225 unit. I spent a lot of time cleaning dirt and mud out of the 225 and then searched the internet for information. My intent was, and still is, to get this old beast running as good as they day it was made. If it wasn't, then I would of not bothered to take the unit or search for info on it, or come to this forum for advice. My comment, regarding "using it for spares" merely means it will be put away, somewhere safe and sound with all my other old stuff - some of which I have had to use for donor chips to get some SBC and other boards operational. It would indeed be a sad, sad day that I would need to pull it apart for bits. Once again, I apologise if my comments caused you angst. Now, back to the 225 issue. Yes, the disk drive array is a blue-box, twin-floppy unit that sits atop the main unit. The main unit has the two-board set that is required to run this double-density drive array. I have contacted the seller to ensure there isn't a cable left behind. Hopefully he has it still and that will be great. If not, I am more than happy to wait for pin-outs and, once supplied, I will make the cable. The other blue-box is the expansion chasis that sits under the main unit to give it a few more slots. I haven't powered up or even cleaned the disk-drive or expansion unit yet. They'll be done during the week. In the interim, I'm reading through the pdf files that you have kindly pointed me to. As per your advice, I won't be pulling apart the unit or do anything untoward until I get more information regarding boot disks and cable pinouts. The iPDS was a freebie given to me when I purchased my initial MDS Series4 some years ago. I have found very little information on this unit and therefore it has been set aside and I thought, "why not ask about the iPDS while I'm here" and it's good to see that there are some people out there that can help me get this unit operational. Other than that, I have no idea about this box - though I'd dearly love to get it going. I do have an old 486 DOS machine with 3 and 5 inch diskette drives, so I can get the iPDS disks done on that machine. My aim, with all this old stuff is to fix it as my main task. I don't collect things (like chip collectors) for looks. I like and want (almost have an inbuilt urge) to make it work and I love to have them all operational. I have fixed and have operational my old SC/MP, 6800 Micro Module, Central Data 2650, AIM65, STD bus and various Intel SBC systems - however, the old TI99/189 system (and a few others) have eluded me for quite some time, but I won't give up on them. Furthermore, I have an inventory of old processors, memory and peripheral chips and, using the Series4 with ICE85B, I build 8085 systems. I am hoping the 225 gets operational so I can do some stuff with the 8080 chip - like do some old S100 work and repairs on an SBC80/24. I'd love to build an 8080 system also. So please, don't think of me as a destroyer of old systems. I'm a preserver, who should of used a better phrase than "used for spare parts". :) I do hope you accept my apology, and I am extremely grateful for your assistance and advice. seeyuzz river