Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!ll-xn!ames!amdahl!dwl10 From: dwl10@amdahl.amdahl.com (Dave Lowrey) Newsgroups: comp.sys.cbm Subject: 1581 - Review & Questions Message-ID: <14031@amdahl.amdahl.com> Date: Thu, 10-Sep-87 11:31:46 EDT Article-I.D.: amdahl.14031 Posted: Thu Sep 10 11:31:46 1987 Date-Received: Sat, 12-Sep-87 08:52:28 EDT Organization: Amdahl Corporation, Houston TX Lines: 126 Keywords: 1581 3.5 inch disk drive commodore c64 I just purchased a Commodore 1581 disk drive for my C64. I thought folks out in netland would be interested in a review.... Physical: The drive is small (63mm high, 140mm wide, and 230mm deep), with an external 10 watt power supply. It uses "Any good quality 3.5 inch double sided diskettes"(quote). I bought a box of Memorex single sided quad density disks (the only type in the store) and those work, but I plan on buying true double sided disks in the future. After formatting, a disk has 3160 free 256k blocks avaliable for storage. Logically, a disk has 80 tracks, of 40 sectors each. The directory track is on track 40. Three sectors of track 40 are used for the disk header and 2 BAMs, which leaves 37 directory blocks. This yeilds a maximum of 296 files per disk (excluding partitioning, see below). Sequential files can contain up to 802,640 bytes. Relative files can be up to (approx.)800K with a maximum of 65535 records/file. For those interested: The disk actually has 80 cylinders, 2 tracks (sides) per cylinder. Each track contains 10 512 byte sectors. The drive translate the logical mapping to the physical and vice versa. This allows (theoretically) the drive to read disks created for other machines (mac & pc), as it can be set to read other block sizes. Interface: The drives uses the standard CBM serial interface. It has external dip switches to set the device's address to 8,9,10, or 11. The drive recognizes the "standard" CBM disk commands to open, read, write, etc. There are also a set of "burst" commands for reading the disk in it's native mode(s). Access times are bit faster than a standard 1541, because the drive buffers a whole track at a time, so subsequent access to sectors on the same track require no disk seek and access time. This makes directory searches MUCH faster, and sequential read/writes and saves/loads appear to be about 1/3 faster (very unscientific measuring). However, as would be expected, my fastload cart. doesn't work with the drive when trying to load. Partitioning: The 1581 introduces a new feature called partitioning. This feature allows you to designate a particular area on the disk as being protected, as if a file resided there. Thus, the Validate command will not reclaim any of the blocks in the partitioned off area. For those of you who do direct access programming, this is a big help. The real benifit of partitions is that you can create a new 'virtual disk' within a partition, complete with directory and BAM. You can then create a new partition within a partition, etc. This somewhat resembles the UNIX file system structures. There are limitations however. You can only access files in the "current" partition. You can change the current partition to be one of the partitions in the current directory, but to go back "up" the tree, you first must go all the way back to "root' (/) and go down to the desired partition. I plan to use this feature to keep my C-Power sources straight. I can have one disk for all of my sources, but each group of programs will be in it's own partition. A partition is listed as file type "CBM" in a directory. Software: The drive comes with a TEST/DEMO disk containing many programs. Most are newer versions of the standard CBM disk stuff. However there is a very nice sector editor that works with all types of CBM drives. Also are samples of code using Burst mode (128 only), a partitioning aid, and several different disk copy programs. Documentation: The documentation is fairly good. It describes all of the disk commands (scratch, rename, load, save, etc.) and how to do them with both BASIC 2.0 (C64) and BASIC 7.0 (128). It then goes on to give programming info for Sequential files, Relative files, Direct access, and Internal disk commands (memory read, memory write, etc). Next, the format of the Burst commands is describes. There aren't any examples in this section, so it can be a bit confusing. Finally, there is a "internals" section, complete with a DOS memory map, a description of the controller job queue, and a description of the vectored jump table. A set of appendices describe changing device numbers, dos error messages, disk command qwick reference, 1581 specs, and serial bus information. Impressions: - The biggest drawback to the drive is loosing the fastload ability. So, I will use the drive for data storage, but not many programs. - I would also like to see a fast copy program. I calculate a full disk backup time of 45-60 mins (not including floppy disk swaps!). - Altho the disk is much larger, the still havn't increased the number of buffers in the drive (excluding the whole track buffer). Therfore, you still have the same limits on the number of open files. - There isn't any support (yet) for the 1581 in GEOS-64. Questions: (Listen up Commodore :-) ) 1. Can burst mode be used on the 64? If so, is there a "fast" serial bus driver avaliable? 2. The burst mode source file on my demo disk is trashed. I tried to print it, and after 5 or 6 pages, the file is garbage. Is it just my disk, or are all of them that way? If it is just my disk, can I get a new one? If they are all that way, can I get ahold of a good copy? 3. There is a program on the disk called zapload.64. It includes a fast loader that works with all CBM drives. Can I get ahold of the source to this program? (I know, get the ol' disassembler out, right?) 4. The drive has the capability of automatically loading a file into one of it's buffers, and executing that program upon drive initialization. This is documented in the 1581 manual. I know that this feature was also on the 1541, but undocumented. My question is... what the heck good is it? What would you use it for? I am making the rash assumption that it is there for a purpose. 5. Is "save with replace" safe to use with the 1581? 6. Are there any known bugs with the drive? Final Words: I bought this drive for it's storage capacity. The faster sequential/ relative file access is a plus also. The drive seems to meet all of my expectations on those points. I sorely miss the fastload capabilities, but I expected that when I bought the drive. The drive delivers what it promises, and I would recomend it to anyone needing a large amount of storage capacity. -- ------------------------------------------------------------------- "Familiarity breeds attempt" Dave Lowrey Amdahl Corp. Houston, Texas (713)-850-8828 ...!{ihnp4,cbosgd,hplabs,oliveb}!amdahl!dwl10 [ The opinions expressed be those of the author and not necessarily those of his most eminent employer. ]