exxos's Atari, Amiga & retro forum

Reluctant16bitter wrote: 29 Aug 2025 15:20

rubber_jonnie wrote: 29 Aug 2025 15:15There may be something that needs to happen with R111 & R112 as there seems to be jumper wires in place there. I have seen jumpers that are bridged with solder on some boards to enable the blitter, but I can't recall if that was ST or STE.

I'd have to look at the schematic or another STE to check how they should be configured though, and I can't look at mine because I'm on holiday right now. Perhaps have a look at the mainboard images section of the forum.

What's going on with the duct tape BTW?

This, except for the new PSU and the 4MB worth of SIMMs that I put in yesterday, is how I bought it from someone who didn't have a clue about it (he was emptying the attic of someone who died) so I haven't the foggiest about the duckt tape, any of the wires or the R111 and R112. As far as I know, this is how in 1988 Atari rushed out these devices from the factory and put a big metal shield over it to hide their workmanship.

I'll have a look at the schematics I can find. And enjoy your holiday!

OK, weirdly my other post vanished.

It looks like, based on this: STE Mainboard that the wires in R111 & R112 were added to disable the Blitter.

They don't look very factory, so I'd suggest maybe the blitter was robbed for something else and they'd probably beed to go to ensure any Blitter you installed worked.

That does indeed look like a whole lot of not-blitter beneath all those retaining straps! :lol:

I think the obvious conclusion is that it's been pinched for something else.

STFMs with boards that are fitted for-but-not-with blitter normally have the space for the socket but no socket fitted and STEs with the integrated blitter again normally have the space, but no socket fitted. The fact you have a socket (and the straps!) reinforces my opinion, I think.

Cheers,

BW

Badwolf wrote: 29 Aug 2025 15:29 STFMs with boards that are fitted for-but-not-with blitter normally have the space for the socket but no socket fitted and STEs with the integrated blitter again normally have the space, but no socket fitted. The fact you have a socket (and the straps!) reinforces my opinion, I think.

Yes, it seems you're right. So if I buy a blitter on Ebay and replace those odd wires at R111 & R112 with the correct (which?) jumpers, will it then work, or is there more I should do?

Reluctant16bitter wrote: 29 Aug 2025 15:42

Badwolf wrote: 29 Aug 2025 15:29 STFMs with boards that are fitted for-but-not-with blitter normally have the space for the socket but no socket fitted and STEs with the integrated blitter again normally have the space, but no socket fitted. The fact you have a socket (and the straps!) reinforces my opinion, I think.

Yes, it seems you're right. So if I buy a blitter on Ebay and replace those odd wires at R111 & R112 with the correct (which?) jumpers, will it then work, or is there more I should do?

Those links are to bypass the bus grant chain that would normally go via blitter. They just need to be removed (or cut) if a chip goes in.

From the schematic (available at dev-docs.org):

U101 is 'STB': ST Blitter.

BW

Right. So, just to be sure, I just need to cut/remove those wired and not replace them with jumpers like the ones next to them?

Badwolf wrote: 29 Aug 2025 15:29 That does indeed look like a whole lot of not-blitter beneath all those retaining straps! :lol:

I think the obvious conclusion is that it's been pinched for something else.

STFMs with boards that are fitted for-but-not-with blitter normally have the space for the socket but no socket fitted and STEs with the integrated blitter again normally have the space, but no socket fitted. The fact you have a socket (and the straps!) reinforces my opinion, I think.

I wonder if the machine had an accelerator fitted at some point? If I remember correctly, some of them required the Blitter to be removed (and it was effectively redundant because the accelerated CPU can move the data as fast as/faster than the blitter anyway).

I certainly don’t think Atari ever sold STe's without blitter chips (either as a discrete chip, or built into COMBO) — it wouldn’t be compatible with STe software if they had…

Steve

Sorry for asking again, but I'm quite new to Atari computers. So I found a C101643 on eBay and https://www.best-electronics-ca.com/custom-i.htm seems to confirm this is an STE blitter. Am I right?

Reluctant16bitter wrote: 29 Aug 2025 18:05 Right. So, just to be sure, I just need to cut/remove those wired and not replace them with jumpers like the ones next to them?

Correct. Those wires are “zero ohm resistors”. The chip, when present, connects those lines as required. There should be nothing across the “R111” and “R112” terminals when the chip is fitted.

BW

Reluctant16bitter wrote: 30 Aug 2025 08:46 Sorry for asking again, but I'm quite new to Atari computers. So I found a C101643 on eBay and https://www.best-electronics-ca.com/custom-i.htm seems to confirm this is an STE blitter. Am I right?

Yes. That's a blitter, although it may not be from an STE. They can be in different systems e.g. MegaST. Only on later STE revisions it got moved/integrated into another IC.

Atari blitters are functionally the same with no pinout changes - although there are minor revisions of the logic and the early ones had a bug (with a bodge-wire workaround on the board).

Should be possible to identify from the part code if it's the older, buggy version or not. If its a later revison it should be fine in the STE.

(I have an STE here I can take a look and see what part number it is using.... - nope, mine has the integrated blitter apparently)

A bit of digging indicates that C101643(-011) is a revision from 1987 and predates the STE by a good margin. It's probably a MegaST blitter. However from what I can tell from other theads about blitters, this revision has been tried and 'works' in STEs.