sup8pdct

I have always been wondering why could atari release such a terrible drive. I had a xf551 and it broke in a few years. I hated the slow I/O, and the drive went crazy when you switched disks with different formats. The nicest part of this drive were the possibility to hook up a 3.5" mechanic in it (and change eprom). And I liked the XE look very much. But as I said: It broke very soon. I don't have the parts anymore. Greetz Marius When the XF551 first came out here in Australia, they wouldn't work. It needed a rom upgrade from V7.0 to 7.07. When the drive was programmed, they didn't take into account the slightly different timing of the PAL computers so the serial bus speed was out of spec for Pal computers. I compared the roms and there is only about 8 bytes different. CSS did 3 things for the XF551. one was a duel drive upgrade which I got. It also didn't work on PAL computers so I sent off the Differences to the creator and he duly fixed it. The duel drive upgrade makes the xf551 handle more like a 1050 but double sided and with a 3.5" mech as well in the one drive. James

The one I have is axlon compatiable. A single wire needs to be soldered to the rom board so the switching address is at $CFFx I will need to find everything first! James

Atari developed the 1090XL pbi box. I have one here but no cards. Have seen a Z80 card and a memory card. The guy I got this unit from worked for a HDD company and they where developing a HDD card for the unit. The unit has 5 slots PC style but a bit wider. The box has what looks like 9V ac power in socket. Unit has Has buffering chips for the parrallel bus. All memory address decode must be done on the inserted card them selves. Very nice unit. pity atari dropped it. check out here http://atariki.krap.pl/index.php/1090 James

If I dig around, I just may find a add on board for the middle ram board for the 800. It requires an original board, several cut tracks and soldering. 8 256X1 ram chips. It will help greatly if the covers are removed from all the ram modules and the os rom module. The late 800's didn't have any covers and the boards had a single plastic spacer to hold them still. James

>Atari originally had a low-density format that netted you about 90K per disk (810) this one come in 2 types. one without a data separator and one with. also 2 different mech were available One had a reputation for not centering the disks properly. >Then they developed a double density drive but never released it (815) There is a version of dos 2.0 (2.0D) that was for this drive. The dos leaked out, the drive didn't. >A big list of 3rd party drives appeared that supported the double density mode. >Atari invented a new "Dual-Density" drive that fell in between single and double density (1050). The only rationale for such a move is that it made the drive >electronics a little cheaper. More like what ever mode the disk was formated in, Dos 2.0S could still read it, tho not to full capacity. The electronics saved was 128 bytes of ram for the sector buffer. The 1050 has the most upgrades available for it as well, making it the most useful or all drives to have. >A big list of 3rd party drives appeared that supported single, double, and dual modes. >Atari's last 8-bit drive supported all modes, plus double sided disks. (XF551) Also support for high speed SIO tho it is the slowest of all high speed that were already available from 3rd party vendors. A couple of upgrades are available for the XF551. James

There is an indusGT diagnostic disk avilable too check out http://ape.dyndns.org:8083/BRADFORD/ I put it there many years ago. James

Superdos 5.1 only uses double sided with a normal XF551. any enhancement for the XF, Superdos sees it as a SuperMAX or USD drive. USD format command includes a sector order. Your XF should format 180K fine at high speed. Superdos was written to be very similar in size to dos 2.0S and also compatiable with it. I have the Full Source here somewhere written in Syn Assembler with no comments what so ever. James

Those extra caps soldered directly to the chips are to make it stable. Apperantly, ICD used to add caps to make it stable before shipping them out. I found I had to add extra ones my self to make it stable for both XL and XE. also note that one of them isn't connected to anything. PS. one cap has 33 on it, the other one has 68. James

Actually, I dont know. heh. The one I have for R&D didnt come with one either.. But.. looking at the design, it has a full-wave rectifier, and uses a 7805 regulator for the +5v, and a 78L15 for the +15v.. Both these devices have a max input voltage of 35v.. The 7805 is a 1amp regulator, and the 78l15 is 100ma... So to be safe, Id say the psu should be able to deliver between 18-30volts AC, 1000ma... Theres no way the device will draw this much current, but for stability's sake.... I ran mine from 9VAC ie a 1050 power supply. It worked fine, even the serial port. Mine doesn't have the 78L15 (re earlier post). also it the 78L15 is at the end of a voltage trippler circuit so 9V ac is fine. James

Actually, I dont know. heh. The one I have for R&D didnt come with one either.. But.. looking at the design, it has a full-wave rectifier, and uses a 7805 regulator for the +5v, and a 78L15 for the +15v.. Both these devices have a max input voltage of 35v.. The 7805 is a 1amp regulator, and the 78l15 is 100ma... So to be safe, Id say the psu should be able to deliver between 18-30volts AC, 1000ma... Theres no way the device will draw this much current, but for stability's sake.... I dug out my MIO and had a look at it. Mine doesn't have a 78L15 (VR2) , C42, C43, D6, D1, J8, J7 or J10 installed. I does have a couple of extra capactors soldered directly to chips , a resistor from TP3 to Gnd and some small wires added. Pic here http://www.eftel.com.au/~sup8pdct/mio.htm It was for the never released 80 colum board. one thing the MIO does that the BB doesn't is invert the data sent via the scsi bus (and the printer port) hence data stored on the HDD is also inverted due to the MIO hardware design. That means commands sent to the HDD controller must be inverted by the driver before being sent. That is why the BB has a MIO compatiability mode. James

I upgraded a mates MIO from 256k to 1 meg. I had to change the rom before it would see the 1 meg. I latter looked at the roms and found 1 byte difference (from a 40 yo memory). ie number of pages of ram to expect. Not a fun job upgrading the ram either. Cleaning out many holes adding the Zipchip ram and then adding capactors to make the thing stable again. James