U1MB hookup points mapped on 800XLF PCBs

[Beeblebrox]

One of my 800XLs has a 800XLF motherboard, which has a Freddie chip and as I discovered a slightly different PCB configuration/layout to other 800XL (non Freddie) PCBs. (My particular one is a C025925-001 Rev R3 800XLF for the record.)

 

I installed the Ultimate 1MB (white PCB version) upgrade into my 800XLF earlier today and thought I'd share the following should it help anyone.

 

Among other things the excellent U1MB 800XL install video by @flashjazzcat here shows you where to hook up the 4 x wires that link the U1MB to the 6502's 4 x legs for PHi2, R/W, RST, and HLT. This saves you soldering directly to the legs of the CPU itself which from personal experience in a previous XE based U1MB install I've done is a lil tricky.

 

However as yet I don't recall seeing anything anywhere that shows where these points on the 800XLF boards are, given they differ slightly from regular 800XL boards. So I decided to map them. I contacted FJC (thank's Jon), and got a little advice a few weeks back. In the end my trusty multimeter was great in confirming the points.

 

Here is an overall shot of the board with the 4 x indicated:

 

This is the image showing the legs of the CPU in question:

 

(Source here from Retrolemon)

 

PHi2 links to CPU pin/leg 39, which can be hooked up here off the R20 resistor's lower solder point:

 

 

 RST links to CPU pin/leg 40 and can be hooked up here on the board next to the OS rom chip socket, (which I believe is the same as standard 800XL boards):

 

  

 

 

R/W links to CPU pin/leg 36 which can be picked up here:
 

 

 

Finally HLT links to CPU pin/leg 35 which can be picked up here:

 

   

 

After installing it my 800XLF booted fine with no issues:

 

 

 

Edit: Also worth a mention given we are talking about 800XLF boards with Freddie chips. FJC kindly informed me also about the following 5V Freddie power issue which may surface with these 800XLF builds, where there is a simple fix as advised by Tf_hh. See this vid for details. I've not done the mod on my 800XLF as yet but may well do as very quick and simple. (FYI I've not got an VBXE installed)

Edited August 11, 2021 by Beeblebrox
adding more info

[_The Doctor__]

this is the link

https://atariage.com/forums/topic/185028-found-an-issue-on-instability-effects-on-a-800-xl-with-freddie/?tab=comments#comment-2327265

 

and some other points of interest

 

https://atariage.com/forums/topic/260267-the-uav-rev-d-video-upgrade-thread/?do=findComment&comment=4079417

 

this gets right to what needs to be handled without sifting through noise or searching through video.

Edited August 11, 2021 by _The Doctor__

[abbotkinneydude]

I guess this would work with the SECAM-ROSE 800XLF?

 

I have yet to attempt a U1MB install on those.

 

Thanks.

[Beeblebrox]

40 minutes ago, abbotkinneydude said:

I guess this would work with the SECAM-ROSE 800XLF?

 

I have yet to attempt a U1MB install on those.

 

Thanks.

Could be if the board looks the same. Just test the cpu's legs in turn with the points referenced in the images to see if you get a connection. Good luck.