| ??? 07/09/07 08:01 Read: times |
#141591 - why that fast? Responding to: ???'s previous message |
Richard Erlacher said:
The MFM data was stored at 5 Mbits/sec, so there are 83333 bit windows per rotation, nominally, and, if one samples at 8x that rate, or 40 MHz,[...] OK, that's 5MByte / s for me, if you deserialize the data. It's a digital stream coming out of the drive, I hope, not the raw analog output of the head amplifier... ? It also means 83kByte of data per track, isn't it. Richard said:
[...] digitally synchronized with the data from the controller,[...] Do you really need that sort of synchronisation? I thought the point of using oversampling is to be able to "digitally lock" to the captured data afterwards... I mean, you could greatly simplify the capturing hardware if you simply capture at a fixed rate. Richard said:
No, the data doesn't have to be processed on-the-fly, but it does have to be captured in real time, and transmitted to the PC while the next track is being "formatted" and at a rate sufficient to ensure that the controller doesn't overwrite its previous track. I still have problem to understand why do you want to transmit the data at full speed. I thought, you could capture a single track, stop the capturing, transfer it to PC at whatever rate available, and only when the track has been transferred, tell the drive to move on to the following head/track. At least this is what I would try to do. Is it too complicated to move between heads/tracks? Do you need the controller to be involved in this? How much control do you have over this? Jan |
