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Well, I have been somewhat successful, but I'm not sure why. It *seems* like if I use CTOD first to copy a file, then CDIR works. But if I do CDIR before doing CTOD, I get the sector not found... I only noticed it because I use CMENU to format a new blank disk, the used CMENU to copy a...

Thanks for the info! I dug a bit more, and indeed it is mentioned in a few places that some of the Crememco setups have the first track single density. I would like to be able to read/write these disks with 22DISK, so I set out to build a config. I can read these entire disks just fine in...

I'm working on restoring an old IMSAI 8080 I recently acquired. The system itself looks to have been sitting for the last 30 years or so. I removed everything and checked the power supply first, which measured perfect. I installed the cpu card and a ram card and the system came up without any...

Thanks Hugo. I'll take a look!

Ah yes, that makes complete sense! I was not considering the need to generate the RAS/CAS signals on the dynamic RAM board, and the somewhat tight timing that implies. Thanks for the detailed explanation. I thought the refresh technique used on the CCS2065 was pretty interesting, being able...

Thanks so much!... I missed that location for looking for the manual or schematic. Sweet! One other somewhat related topic - I believe there are subtle difference between a system that has an 8080 vs one that has a Z80 in regard to RAM boards. One of the dynamic ram boards I have has a...

Is anyone familiar with this S-100 64K SRAM card? It says "Mariposa Design Group" on the side, and has 64K of SRAM. Each SRAM has a small jumper that is labeled RA/RO (Read Only?). The center of the PCB has a set of 4 jumpers labeled X0/G0 to X3/G3. Another jumper labeled GB, and...

Speaking of mistakes! BANK0_ADDRESS_ACCESS = laaddr_field:['h'01XXXXX]; /* Second Megabyte of System Memory */ BANK1_ADDRESS_ACCESS = laaddr_field:['h'02XXXXX]; /* Third Megabyte of System Memory */ BANKN_ADDRESS_ACCESS = BANK0_ADDRESS_ACCESS # BANK1_ADDRESS_ACCESS; Those field values (at...

Oh yes, you can download the version that is the default trial and that might be sufficient. I"ll check the pin count. I started a new thread : https://forum.vcfed.org/index.php?threads/building-a-5170-memory-card-for-all-system-memory.1242484/#post-1307781

Controls for the SRAMs - CS is the key for selecting which SRAMs are on. Control for buffers. Those last two could be one, because you can drive all 16 data lines even if the CPU is only reading one of the two 8 bit paths. There is a near 100% certainty that there are mistakes here and in...

And the CPLD code: (Open Collector for those ISA signals. It could also be tri-state, but I think OC will work) Input pins, from ISA bus, plus a 4 dip switch for config. Outputs - Back to ISA, plus controls for SRAM and buffers. Latch for LA address bits. Not entirely needed as...

First pass at a PCB:

Initial Schematic:

I have a couple of 5170 systems, and one of them has significant number of bad DRAMs. While you can still get some of stacked DRAMs from ebay, the supply isn't huge, and the cost to replace all 512K is pretty high. Based on a conversation between a few other members a while back...

I did a few tests on my TYPE-1 5170 motherboard with 512K installed ( And J18 set for 512k) First up is U64 Pin 12 (RAM0CAS), which shows normal traffic during idle operation. Next up is U64 Pin14, RAM1CAS, showing activity because I was running a memory test that was working in that upper...

Ah interesting. I'll take a look on my board and see what it looks like. It is certainly possible the schematic is not perfect. As I understand it the XT schematic has a few mistakes in it. You should see both RAS lines during refresh doing the same thing, but otherwise you would not see a...

Welcome from a Portlander! Great to see BBSs still going strong. Nice system with some great overclocking!

Welcome!

Hello from Portland, Oregon - Vintage enthusiast, electrical engineer, was an engineer at Intel in the 90s. Enjoy microprocessor design, implementing designs in hardware, CPLDs, and FPGA. A good amount of surface mount work, plus the firmware and software goodies that go with it. I have a...