800 memory upgrade

[800 memory upgrade]

I have read several comments about 256k and 288k memory upgrades for the atari 800. I would very much like to build one but I haven't been able to find any diagrams or pictures. Can anyone help me out here.

 

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

[Shut up and drive]

>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

[Indus GT Woes]

There is an indusGT diagnostic disk avilable too

check out http://ape.dyndns.org:8083/BRADFORD/

I put it there many years ago.

 

James

[Hyper-XF with superdos 5.1]

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

[NEW MIO production run.]

Excellent picture...

This is the latest serial number build I have seen to date..

 

Notice the larger, higher wattage diodes in the rectifier stage, and how the board is not delaminated, or discolored there. (good fix. Where have I heard that before? heheh)

 

Notice the "blue wires" done on the component side of the board this time, instead of the back side.. This is a propogation timing fix for the A8 adress line. It runs through 2 extra inverter gates in series (pins 1-4 on U7) to delay the assertion of A8 slightly within the bus cycle. All MIOs have this, but its wired on the solder side of the board on earlier built units.

 

Notice the 2 extra 33pF caps on U1... This is the first Ive seen of this..

 

Notice that none of the extra pin headers (extra power, video, or extra 50pin bus) are populated.. Also notice that the 2 electrolytic caps and 2 diodes (voltage doubler) as well as the 78l15 regulator are left out. And.... The DB9 external Video connector is left off!!! By this stage in the game (serial number 1688,) ICD was DEFINITELY not planing to put an 80 column card in this box.

 

Kewl picture. Thanks alot. I will add it to my collection.

 

 

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

[NEW MIO production run.]

What is the specs for the PS? I just got a MIO and it did not include a PS.

 

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

[NEW MIO production run.]

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

[(Old) MIO 256K vs. 1MB Roms]

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