PET index - peripherals Tape Drives The first peripheral to work with the PET were the tapes. In fact the tape recorder was built-in into the first PET machines with the chicklet-style keyboard. A connector was available at the back to plug in a second tape recorder. Since the first PET all PET models have two tape connectors at device #1 and #2. But only one of them can be working at a time - first, the CPU is in use of course and secondly some lines from the tape ports are shared between the ports. Transferring files with a tape The PET tape recorders are compatible with the C64/VIC20 tape recorders so you can simply use one of those. There is one problem, however. All these computers run at different frequencies (also depending on the PAL/NTSC issue), some slightly above and some slightly below 1 MHz. Fortunately the PET run exactly at 1 MHz, in the middle, and can therefore exchange files with all the other computers. In fact it was proposed to use a PET in between a VIC20 (above 1 MHz) and a C64 (below 1 MHz) because the tolerances allowed the C64 to read the PET but not the VIC20 and vice versa... The PET FAQ contains some info on tape problems etc. -------------------------------------------------------------------------------- Disk Drives After the first ROM revision Commodore made the IEEE488 interface work. It was already in the machines, only the disk drives were not ready so the IEEE488 routines could not be tested... Disk drives to be used with the PET have to be equipped with the IEEE488 interface. Most of the devices had two drives, the 2040, 3040, 4040, 8050 and the 8250. The disk capacity ranged from 170k (2040, 3040, 4040) over 512k (8050) to 1M (8250) per disk. The 2040 (and 3040?) had CBM DOS 1.x, without relative files, while 4040 and 8050 had DOS 2.0 and 2.1. DOS 2.5 and 2.7 were then later used in the 8050 and 8250 drives. The 2031 and SFD1001 were single drive, low profile versions of the 4040 and the 8250 drives resp. Those drives had two 6502 processors (i.e. one 6502 and one 6504) one for the drive control and read/write operation and one for the IEEE488 transfer and file handling. The DOS parts for both CPUs have been put together for the single CPU VC1541, that still has the disk controller code in the interrupt routine and the file handling outside... There were even 8" disk drives (8060 w. 750k, 8061 w. 1.5M) probably with DOS 1.x, and later the 8280 with DOS 3.0 and even harddisks with DOS 3.0 and 5M (D9060) and 7.5M (D9090) capacity. For more information see the CBM products list. Here is an overview on some of the drives (admittedly copied from the C64S homepage, but only because I did not find an electronic version of the VC1541 manual with the same info...): Model 2031 4040 8050 8250 DOS version(s) 2.6 2.1/2.7 2.5/2.7 2.7 Drives 1 2 2 2 Heads per Drive 1 1 1 2 Storage Capacity 170K 340K 1.05MB 2.12MB Buffer Storage 2 4 4 4 (K) Tracks 35 35 77 77 Sectors per 17-21 17-21 23-29 23-29 Track Bytes per Block 256 256 256 256 Free Blocks 664 1328 4104 8266 Location of 18 18 38/39 38/39 Directory Directory 144 144 224 224 Entries Transfer Rate (K/s) 40 40 40 40 internal 1.8 1.8 1.8 1.8 IEEE/serial bus Access Time (ms) Track to Track 30 30 5 5 Average Time 360 360 125 125 The PET FAQ has some info on the blinking codes when the disk drive doesn't work. Some schematics and ROMs are also on the archives. Transferring files with disk The 170k versions (2040, 3040 and 4040) are not completely compatible to the VC1541 format. At least our schools 3040 had one additional sector per track in one of the speed zones. The 4040 has the same number of sectors per track, but the write gap between the sectors is different so that it is only read-compatible with the VC1541. This means simply write the files on one disk type only, and read it on both types. Transferring files using IEEE488 So if you have a 170k drive with your PET you are lucky, but what if not? It is possible to modify a VC1541 to have an IEEE488 interface. This includes some soldering and burning an EPROM with a new ROM. Schematics and listings can be found on the IEEE488 page. It is also possible to build a converter from parallel IEEE488 to serial IEC bus - the protocol is the same, only the hardware differs. It can also be found on the IEEE488 page. [I use the modified VC1541, a friend of mine uses the IEEE488 to IEC converter] Other transfer methods There is one program that can be used with many Commodore computers, written by Marko Mäkelä and Olaf Seibert. It is called prlink and a link is on the page. -------------------------------------------------------------------------------- Back to the PET index PET index V0.9 (c) 1998 A. Fachat