flash programmer - payload buffer

[Altera_Forum]

I have build a custom board equipped with a cyclon 1c20 speedgrade 8 and an epcs4 flash for configuration and program storage. The board runs at 50MHz and i use the USB-Blaster to connect to the JTAG interface. Now, as i had to update to quartus & nios2 Version5 (+ SP1), i had the same flash programmer issues as at every version i installed before and so i deceided to start a discussion about the payload buffer size. 

 Everything started as i ported the FlashProgrammer as described at the user guide for the first time. After following every step, there was an verify error at every programming cycle.  Disappointment appears...  After hours of debugging i got the right idea - maybe my computer is to fast (I use a 2.8GHz Pentium running XP) - because the progress bar at the read and write operations took several steps at once. To slow the things down, i created a flash programmer design with only the minimum (512 bytes) payload buffer - and from this point of time, every programming operation works flawless - if i use this (slow) design.  So my question - is there an error at my board or is this a common problem of which i haven't heard of?

[Altera_Forum]

Same problems here. We use speed grade 8, although I don't know if that's the problem. I went through several iterations with mk_target_board using different clocks (above and below 50MHz) and different payload buffers. It seems that smaller payload buffers work better but I don't think that's the whole story. It seems to be a combination of host USB, PC speed and payload buffer. Generally speaking, there seems to be some kind of synch problem between the USB blaster and the Cyclone. I can't get it to work on my USB hub but it does work with the built-in port. I also couldn't get big payload buffers to work at all. Luckily we have piles of different PCs in every cube so we can find a combination that works. 

 Andrew