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Old 28 December 2017, 17:26   #1
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Comspec SA-2000

The Comspec SA-2000 seems to be more or less a Zorro II version of the SA-1000 so should be easy to support in WinUAE. It uses the same ROMs as the SA-1000. [From the filename, comspec-2000.dms (which works with the SA-1000) may have been supplied with an SA-2000 board.]

Word-wide ROM, DiagArea at offset $20.

Differences vs SA-1000:
- SA-1000 supports loading Kickstart from HD and maps its ROM to $F00000, but that isn't needed on the A2000. I'm guessing the SA-2000 ROM appears at $Ex0000 instead.
- No RTC, so bit 0 of er_SerialNumber will be 1.

Looking at the board pic, jumper JP2 is marked 1.2 1.3; presumably the 1.2 position disables auto-booting. Maybe that clears the diag valid bit in ExpansionRom.

There are some unpopulated jumpers/switches: Two switches SW1, SW2 next to JP2. Looks like SW1 has same function as JP2, SW2 unconnected.
JP3 is marked 2764 27128, would be set depending on the EPROM size.
JP4 next to WD33C93A, marked CD CM. Don't know what that would control.
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Old 29 December 2017, 22:02   #2
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CD / CM seems to be the clock source. Jumpered to CM with a trace on the solder side, connecting directly to the output pin of the oscillator.
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Old 30 December 2017, 13:00   #3
Toni Wilen
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SA-2000 is now SA-1000 suboption. It won't be separate device until it is 100% confirmed ROMs are identical and $f0 ROM is the only difference.

EDIT: Made it real sub option (like supradrive series). Config is not anymore compatible, SA-1000 must be re-added manually first.

Last edited by Toni Wilen; 30 December 2017 at 14:06.
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Old 30 December 2017, 16:36   #4
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The amiga.resource.cx board pic shows two EPROMs in U15 and U16 positions, labelled
P91-01607    P91-01608
  U4/U15       U5/U16
The currently-available SA-1000 ROMs were (from their filenames) labelled similarly except P91-01605 and P91-01606. So probably an earlier version, but saying U5/U16 on the chip label implies they would work in the SA-2000. durniplot recently created a thread about trouble with his SA-1000 and this post shows a pic of his SA-1000 board. The EPROM labels are the same P91-01607 & P91-01608 as shown in the SA-2000 board pic.

The three Comspec SCSI products (SA-500, SA-1000, SA-2000) are probably almost the same hardware-wise, with the same AutoConfig mfr/product number. SA-2000 obviously has no RTC. I guess the SA-500 might have an RTC; a pic of the board would be nice to check that. SA-500 & SA-2000 won't have ROM mapped at $F00000.

Does the SA-1000 need its ROM to appear at both $F00000 and $Ex0000? I don't think it does. I've been trying to understand the boot process. Let's suppose the SA-1000 ROM only appears at $F00000 and its AutoConfig diag valid bit is 0.

At power-on time, does the SA-1000 ROM appear at address 0 instead of A1000 boot ROM? If it does, no problem. The reset vector (offset 4 in ROM data) is $F03800 so execution starts there. If it doesn't, also no problem because the A1000 boot ROM checks for $1111 at $F00000 and jumps to address at $F00004 if so.

On real hardware, you could see whether the A1000 boot ROM code runs at power-on because it flashes the power LED 10 times. If that doesn't happen the SA-1000 ROM must be the first code that runs.

Anyway. The SA-1000 Kickstart-loader routine has run, Kickstart is loaded into RAM. It writes to $F80000 to write-protect the Kickstart RAM then jumps to $FC0002. Now Kickstart checks for $1111 at $F00000 and finds it because the SA-1000 ROM is there. It puts return address in A5 and jumps to $F00002. The instruction there is JMP (A5) so execution returns right back to Kickstart.

Later on Exec scans for resident tags. It scans Kickstart ROM, then the region $F00000 to $F80000 which includes the SA-1000 ROM. So it finds the ComspecHD.device and ComspecSCSI.device resident tags. Thus they get initialised at that point.
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