<I have no idea, however, how you block and deblock I/O with 1K blocks when <you have only 1k in your sector buffer. I suppose I could go back and loo You copy the sector to the 1k ram area and then copy out the desired sector. the real trick is keeping track of whats in ram and if it has to be written back. <at the software, but the stuff I had at my disposal at the time seemed to <work best with a big hard disk requiring the largest available granules <(allocation blocks) and since the logical drives were limited to 8MB and the largest allocation blocks are due to the need to store in ram on a bit per allocation block basis, a bit for every allocation block on the disk. for something like a 8mb disk using 4k blcks that would be 256 bytes! <since CP/M was pretty much a thing of the past, I didn't see any point in <wasting time and resources fine-tuning it. I used it because I had a few <already-paid for cross assemblers and other tools for CP/M. Once a decent <version of the PC-DOS became available, I was sure to make the switch. O <course I didn't realize how long that would be. Nonetheless, once I had a <PC with a '186 processor, I could run the CPM emulator to use my tools and <the more modern hardware to do my work, and the CPM became a relic. Shame. I still use it. And I'm still finding ways to tune it for even more performance. It was the active full time OS amd machine until 89 when I went pdp-11. After that it was the part time on line system. Current project is to add heirarchal directories (not the ZCPR user thing). it turns out to be doable though the bdos will have to be altered. Allison