[cctalk] Re: Odd IBM mass storage systems
On 4/18/24 14:01, paul.kimpel--- via cctalk wrote: > The tape for the Burroughs 220 drives was not metallic. It was 3/4-inch wide, > and I think a Mylar sandwich. It could be spliced much the same way you would > have spliced quarter-inch reel-to-reel audio tape back in the day. > The Datamatic 1000 tapes were definitely a Mylar sandwich affair. 3" wide and 2700' long. https://www.smecc.org/honeywell_datamatic_1000.htm A few reels of the stuff are still around. --Chuck
[cctalk] Re: Apple II
Bill, so the disk drives are gone? Sent from my iPhone > On Apr 18, 2024, at 14:36, Bill Degnan via cctalk > wrote: > > Not sure if you mean me, "Bill", but I sold or gave away all of the Apple's > that I had for sale, about 15 or so all gone. > > I did not have any original II's for sale. Only surplus II+, IIe, IIc, > original MACs (mac plus, SE, classic, SE FD and that style. > > This was all a fundraiser for kennett Classic non profit. > > What's left is here > Kennettclassic.com/surplus/ > > Bill > >> On Thu, Apr 18, 2024, 4:56 PM Adam Thornton via cctalk < >> cctalk@classiccmp.org> wrote: >> >> Mostly to Bill, but also anyone else hanging out here who's got a surfeit >> of 8-bit Apple stuff: >> >> If you're planning on selling the Apple II, and it's not a ][+, I'd be >> interested in buying. Not, perhaps, at optimistic eBay prices, but I have >> a lot of ][+s and //es, most of them in working shape, some of which are >> parts machines; however, I don't have either a II or a //c . >> >> Also happy to trade if I've got things you want. I don't have anything >> super-exotic, but feel free to HMU and ask. >> >> Adam >>
[cctalk] Re: Apple II
Not sure if you mean me, "Bill", but I sold or gave away all of the Apple's that I had for sale, about 15 or so all gone. I did not have any original II's for sale. Only surplus II+, IIe, IIc, original MACs (mac plus, SE, classic, SE FD and that style. This was all a fundraiser for kennett Classic non profit. What's left is here Kennettclassic.com/surplus/ Bill On Thu, Apr 18, 2024, 4:56 PM Adam Thornton via cctalk < cctalk@classiccmp.org> wrote: > Mostly to Bill, but also anyone else hanging out here who's got a surfeit > of 8-bit Apple stuff: > > If you're planning on selling the Apple II, and it's not a ][+, I'd be > interested in buying. Not, perhaps, at optimistic eBay prices, but I have > a lot of ][+s and //es, most of them in working shape, some of which are > parts machines; however, I don't have either a II or a //c . > > Also happy to trade if I've got things you want. I don't have anything > super-exotic, but feel free to HMU and ask. > > Adam >
[cctalk] Re: Odd IBM mass storage systems
The main storage area of the ElectroData/Burroughs Datatron 205 was 20 tracks of 200 words each for a total of 4000 words. The drum rotated at 3570 RPM, so the average access time was about 8.4ms. The four quick-access tracks (or "loops" as they were called) were 20 words each and worked as a delay line, much like the Bendix G-15's drum. These tracks had separate read and write heads. When writing was not taking place, the digits from the read head were simply copied to the write head 36 degrees behind on the surface of the drum. So as the last digit of the track was written, the first digit of the track was coming under the read head, yielding an average access time of 0.84ms. When writing, digits from the processor were shunted to the write head in lieu of those coming from the read head. When power was removed from the system, the 4000-word main memory was preserved, but the data in the high-speed bands was lost. The 205 had instructions to transfer 20-word blocks between the main memory and the high-speed tracks. There were even a couple of instructions to move a block to one of the high-speed tracks and branch to a word in that high-speed track. The high-speed tracks were addressed modulo 20 (i.e., word 4005 was the same as 4025, 4045, 4065, ... 4985). You had to get good at dealing with addresses that were congruent modulo 20. The high-speed tracks were so much faster than main storage that most programmers went to a lot of effort to "block" 20-word segments of the program to the high-speed tracks and execute at least the most active code from the faster storage.
[cctalk] Re: Odd IBM mass storage systems
The tape for the Burroughs 220 drives was not metallic. It was 3/4-inch wide, and I think a Mylar sandwich. It could be spliced much the same way you would have spliced quarter-inch reel-to-reel audio tape back in the day. If the tape controller detected a parity error, it would backspace the block and retry twice. If the error persisted on the second retry, the tape would stop with the head ready to read the bad block (hanging the processor in the middle of its I/O instruction), and the operator would have to take manual action. If the drive punched a hole in the tape, then the drive needed service -- probably a bad capstan pinch-roller solenoid.
[cctalk] Apple II
Mostly to Bill, but also anyone else hanging out here who's got a surfeit of 8-bit Apple stuff: If you're planning on selling the Apple II, and it's not a ][+, I'd be interested in buying. Not, perhaps, at optimistic eBay prices, but I have a lot of ][+s and //es, most of them in working shape, some of which are parts machines; however, I don't have either a II or a //c . Also happy to trade if I've got things you want. I don't have anything super-exotic, but feel free to HMU and ask. Adam
