Eaton.HFED%hi-multics@sri-unix.UUCP (12/06/83)
The answer to a very perplexing question has never beenn satisfactorily answered until now. The question was.... HOW MUCH INFORMATION CAN BE STORED ON A HARD DISK ADDRESSED AS ONE LOGICAL DEVICE? The answer is a MAXIMUM of 8,388,608 bytes and ABSOLUTELY NO MORE than 8,388,608 bytes. I had heard the 8M figure before but no one really explained it so that I understood why. My bios allowed me to make it as large as I wanted to so why not make my 10M hard disk a single logical device. After firing up a quick and dirty "BASIC" program to finish filling out the remaining 3.8M of so far unused disk space (6.2M was already filled with "good" stuff), I let it rip. And "rip" it did. I fully expected to see a disk full message after the mythical 8M or at the 10M limit which my bios was genned for. Well folks... I eventually got the disk full message. However.... It was printed out after my handy-dandy "BASIC" program had written "this is a test message" throughout my entire DIRECTORY! OH $!%*!!! GUESS WHO ORDERED QBAX ONE DAY TOO LATE? As to why this happened I found out with much digging that CP/M will only handle 65,536 sectors (128 bytes each). If you multiply that out quickly in your head the not so mythical figure of 8M pops out with blinding clarity. so.... BEWARE! THE 65,537TH SECTOR IS SECTOR 0! THE VERY 1ST SECTOR IN YOUR PRECIOUS DIRECTORY. MOAN.... SO IF YOUR PUSHING RELATIVELY CLOSE TO THE 8M LIMIT WITH YOUR LOGICAL HARD DISK DRIVES. RECHECK YOUR CALCULATIONS TO INSURE YOU HAVEN'T ALLOCATED 1 BLOCK TOO MANY. signed 8megmax a.k.a Jesse (Mpls, Mn)
POURNE%mit-mc@sri-unix.UUCP (12/23/83)
From: Jerry E. Pournelle <POURNE@mit-mc> If you will send me this in a hard copy message to J E Pournelle BYTE 70 Main St Peterborough, NH 03458 I will pass it along to BYTE readers who will WANT TO KNOW this... JEP