pdp-8/e fault

Thanks for the reply. The list backlog and subsequent mail tsunami means it's a while since I last had a go at the system. I'll run it up tonight and verify what happens. Here's what I can remember. In the manual there's a simple test which counts up in the accumulator. It's entered through the switch register. First you set the switch register to 0000 (Octal) and press the load address. Next you set up the first instruction in the SR and then lift DEP (deposit). The address is auto incremented by one and you enter the next instruction. After the last instruction is in then you load the start address and hit clear and continue and it should count up. It was working but it stopped. If you do examine rather than start you find the memory locations are (I think) still zero. The memory is core with four sets of three boards (4K) making 16K total. Swapping one set of boards with another makes no difference. The switch reg. must be working because memory addresses can be set up. I suspect the memory data bus or associated buffers may have something to do with it. I'll do a detailed check to-night Regards Rod Smallwood I collect and restore old computer equipment with this logo. [digital] -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Philipp Hachtmann Sent: 04 April 2009 12:29 To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: pdp-8/e fault But he wrote that the data displays correctly. The 8/e display shows the state of the memory data bus. My first idea would be to check for bad contacts. And think about the memory control. And? Can you read out memory? Does it change?