• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

Supermac Spectrum/24 III questions

Jamieson

Well-known member
Do the Supermac Spectrum/24 series III cards require the daughterboard for general acceleration?
I'm considering this one but it does not have the daughterboard present.
Also, does this card output sync on green, and can it be disabled?
Anyone have a link to the manual for this card?

spec24.png
 

Byrd

Well-known member
Most didn't have the daughtercard, so let's presume this will output accelerated video with the SuperMac drivers installed. The V1.0 ROM is very early, the card will not function properly on PowerMacs nor System 7.5+, unless you update the ROM with a new chip.

I had a few of these in various Macs, with early ROM they performed at turtle speeds on a 7100/80AV, but good once the ROM was replaced.
 

Jamieson

Well-known member
I'm now the owner of this card. It seems to work OK under 7.5.5. and I'm running it at 1024x768. Redraws and scrolling lags a bit at 24 bit color, but it seems fairly responsive at 8 bit color depth. In the Supermac control panel there a switch for "acceleration" but it is grayed out, due to the card not having a piggyback board installed. Does anyone know of a source to download a newer ROM binary?
 

EmmyOcelot

Well-known member
Fellow Spectrum/24 III owner here, I can't seem to find the v1.1 rom for you online but I do have the rom in mine. It may take me some time but I may be able to dump it. Does the 1.0 rom limit anything that you know of?
 

Jamieson

Well-known member
The 1.0 ROM on my card seems to work OK on my IIci running 7.5.5. It bogs down in 24 bit mode, but I think that's expected without the acceleration piggy back board. @EmmyOcelot if you could dump that 1.1 ROM I could give it try as I have a access to a programmer machine at work. Thanks!
 

EmmyOcelot

Well-known member
I should be able to, though I need to get a new chip programmer as mine bit the dust. When I do get a new one @Jamieson, I’ll let you know and hopefully get that bin file for you.
 

Bolle

Well-known member
Fellow Spectrum/24 III owner here, I can't seem to find the v1.1 rom for you online
Can help with that.

@Jamieson It would be nice if you could read out your V1.0 as well and share it just for completeness sake :)
 

Attachments

  • SuperMac Spectrum24 Series III V1.1.BIN
    32 KB · Views: 17

Jamieson

Well-known member
Very cool, thanks! I'll make my way over to the antique chip programmer at work and get it done. What is the size of this EPROM chip?
 

Bolle

Well-known member
Also, does this card output sync on green, and can it be disabled?
The BT473 RAMDAC that's used on the Spectrum/24 III outputs a composite sync signal on all three analog channels, so it's not only sync on green. The composite sync signal is generated in the L1A4051 Supermac ASIC (probably a gate array?) at U12 pin 50. It's then buffered in the 74F08 at U10 (input on pins 4 and 5, output again on pin 6)
From there it runs to the sync input on the RAMDAC as well as the composite sync output pin on the DB15 connector.
On my card there's two factory installed bodge wires then that connect both hsync and vsync signals from the same ASIC pins 52 and 53 to the corresponding pins on the DB15 output.

So the card will be able to drive either, sync on green (or any other analog channel), composite sync or separate H-/Vsync monitors.
If you want to disable Sync on green you can try lifting pin 6 so it floats and just connect the solder pad to ground.
That way the RAMDAC won't be generating sync signals on the analog channels.

I didn't check if all sync signals are always active or if you can enable/disable them via software so the ASIC only outputs either separate or composite sync.
 

Jamieson

Well-known member
Thanks for the good info on the details on that the Brooktree DAC part. Interesting wire mod on your board with the HSYNC and VSYNC pins. Thankfully my monitor is OK with the composite sync pulse driven on the HSYNC line.

The LCD monitor I'm using doesn't like the sync pulses added to the video signals because the black/blank level gets pushed up above ground, resulting in that "washed out" look. I may try lifting and grounding the "SYNC#" input pin on the BT473 to eliminate those added syync pulses.
 

MacOSMonkey

Well-known member
Can help with that.

@Jamieson It would be nice if you could read out your V1.0 as well and share it just for completeness sake :)
Bolle - thanks for posting that ROM!

IIRC, the Spec/24 III 1.1 ROM (late 1991/early 1992) adds: support for additional monitors -- 16" modes (832x624 for SuperMac and Apple) and RasterOps 19", includes "Quick Panning" (allows you to hot-key pan from anywhere without going to the edge of the screen) and other panning/desktop fixes, fully supports A/UX, improves video timing (including in NTSC and PAL modes -- and maybe also SECAM), many bugfixes and stability improvements (esp. expanded driver spec, accelerator code, startup config and other boot-related stuff) - this ROM should support expanded functionality via the Monitors cdev. And, if you are using A/UX, this ROM is required. The 1.0 ROM had many A/UX-related problems/crashes.

v1.1 removes/disables: "Lock Menubar" functionality (that tried to always keep the menubar on screen when using virtual desktops), custom video timing support, and also virtual desktops in 12" mode (512x384) -- it works on a 12" but only in native resolution. 1.1 was the beginning of the end for the menubar and custom config code. I don't think any other subsequent products included these features.

So, unless the goal is to use a custom config (limited utility, given the wide ranges of supported monitors in 1.1), albeit with lots of other issues, the 1.1 ROM should provide a much better and more reliable user experience. (It was conceptually more like a 2.0 ROM.)
 
Last edited:

MacOSMonkey

Well-known member
And yes, the daughter card is the (PAL/GAL-based accelerator). If it is not present, QuickDraw acceleration will not work.
 
Top