Posted By
Crown
on 2003-09-09
|  Re: Strange 1551
According to Bo Zimmerman's list the 1542 was a serial drive and not a TCBM device.
You are wrong about the 1551 ROM, the hardware in this drives are not like you imagine, there is no additional hardware which magically takes the content of a buffer and pushes it through a serial or parallel channel, this is all done by the CPU with code in the ROM. In case of a 1541 every bytes is decomposed to bits, and each bit is sent individually through the serial IEC protocol, but it is basically the CPU manipulating the wire directly. In the 1551 it is sent through a parallel port, but this is also done with the CPU, but the code is different...
Speed of these machines are not dependant on the frequency of the power supply, first of all the power is converted from AC to DC and in DC land you see nothing from the frequency of the AC signal.
Speed is decided by the clock crystal, and drives released in the States and in Europe has the same crystal, that's why you don't need any modification.
Anyway I got response from the seller, and he told me that this is not a custom modification, but it was sold this way in the shop, so this confirms for me that this is the C64 version of the 1551 drive, and probably was only released in Europe (could be Germany only), and most likely in small quantities as there is no word about its existence on the specialized commodore sites....
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