How tough would it be to clone the Brainstorm? It’s seemingly just a lower power 68000 and a custom bus chip..
Brainstorm Clone?
- Thread starter Ron's Computer Videos
- Start date
The Brainstorm is super interesting and I have never encountered an explanation of exactly what the bus interface chip does. You'd think it would be simple but it's not... the bus interface IC can evidently be reprogrammed by software on the Mac (!). Indeed there is an update for earlier firmware Mac Plus Brainstorms that improves the sound quality/compatibility. And during the update process, the Mac evidently keeps working, otherwise how would it be able to perform the update? Impressive!
@Ron's Computer Videos That looks simple enough to replicate, the PAL/GAL on it could potentially be reverse engineered by @Bolle
That’s the thing, I don’t think it’s a GAL. GALs aren’t in-system programmable and they stop working during the programming process. It seems like some kind of ASIC.
There are a couple of Flash chips (IIRC) on the bottom of the board between the pin header strips.
The Brainstorm upgrade also replaces the TSM chip on the motherboard. Currently the details evade me, but I believe the custom TSM chip handles timing and is what allows the Mac hardware and software to work with the 16MHz 68000.
The following is courtesy of Wouters page on the Macintosh PAL's, here: http://www.retro.co.za/ccc/mac/ReverseEngineering/PALs.html
Apple Mac Timing State Machine, PAL16R8
NB: Not verified yet!
PAL16R8 PAL DESIGN SPECIFICATIONS
16MBUF C16M 8M MU RAMEN ROMEN AS UDS LDS GND
TSEN CAS0 CAS1 RAS TC 1M 4M 2M DTACK VCC
RAS is the DRAM Row Address Strobe.RAS: = /4M * /RAS
+ 8M * 4M * /RAS +
+ /8M * 4M * /2M * /RAS
+ 8M * /4M * 1M * RAS
+ 8M * /4M * /1M * 2M * RAS
+ /8M * 4M * /1M * RAS * LDS
+ /8M * 4M * /1M * RAS * UDS
+ /8M * 4M * /1M * RAS * /LDS * /UDS * /CAS0
+
TC goes to the LAG and to the video counter (U1F)TC:= 8M + /4M + 2M + /1M + RAS
1M: = /8M * 4M * /2M * 1M * /RAS +
/1M * 8M * /4M * /RAS +
/1M * /8M * 4M * 2M * /RAS +
/1M * RAS +
/1M * /8M * /4M * /RAS +
/1M * 8M * 4M * /RAS
4M: = 1M * RAS +
8M * 4M * 2M * /1M * RAS +
/8M * /4M * /1M * RAS +
8M * /4M * 2M * /1M * RAS +
/8M * 4M * /2M * /RAS +
there may be a line missing here.....
2M: = /C16M * /8M * /4M * /RAS
+ /2M + /8M + /4M
+ /2M + /1M + * /TC
+ C16M * /2M
+ /C16M * /8M * /4M * /1M * RAS * /ROMEN * /RAMEN * /AS
+ /2M * 4M
+ /2M * 8M * /4M *1M * MU
DTACK := /C16M * /8M * /4M * /RAS * /AS * /ROMEN * RAMEN
+ /C16M * /8M * /4M * /1M * /RAS * /AS * /RAMEN * ROMEN
+ /C16M * /8M * /4M * 1M * /RAS * /AS * /RAMEN * ROMEN * /MU
+ /C16M * /8M * 4M * /1M * RAS * /AS * /RAMEN * /ROMEN
+ /DTACK * /UDS
+ /DATACK * /LDS
+ /DATACK * /RAS
This is probably not right for the Mac Plus...
CAS0: = 4M * /2M * /RAS * /DTACK * /RAMEN * ROMEN * /LDS * MU
+ 4M * /2M * 1M * /RAS * MU
+ /CAS0
+ /RAS
+ 8M + 4M + /2M * /1M * RAS * /DTACK
+ /CAS0 * /2M + /1M
CAS1: = 4M * /2M * /RAS * /DTACK * /RAMEN * ROMEN * /UDS * MU
+ 4M * /2M * 1M * /RAS * MU
+ /CAS1 + /RAS
| /TSEN0 | /CS | 11 | 10 | GND | ||
| /CASL | O | 12 | 9 | I | /LDS | |
| /CASR | O | 13 | 8 | I | /UDS | |
| /RAS | R | 14 | 7 | I | /AS | |
| TC | R | 15 | 6 | I | /ROM | |
| C1M | R | 16 | 5 | I | /RAM | |
| C4M | R | 17 | 4 | I | VID/u* | |
| C2M | O | 18 | 3 | I | C8M | |
| /DTACK | O | 19 | 2 | I | C16M | |
| Vcc | 20 | 1 | CLK | C16M |
Apple Mac Timing State Machine, PAL16R8
NB: Not verified yet!
PAL16R8 PAL DESIGN SPECIFICATIONS
16MBUF C16M 8M MU RAMEN ROMEN AS UDS LDS GND
TSEN CAS0 CAS1 RAS TC 1M 4M 2M DTACK VCC
RAS is the DRAM Row Address Strobe.RAS: = /4M * /RAS
+ 8M * 4M * /RAS +
+ /8M * 4M * /2M * /RAS
+ 8M * /4M * 1M * RAS
+ 8M * /4M * /1M * 2M * RAS
+ /8M * 4M * /1M * RAS * LDS
+ /8M * 4M * /1M * RAS * UDS
+ /8M * 4M * /1M * RAS * /LDS * /UDS * /CAS0
+
TC goes to the LAG and to the video counter (U1F)TC:= 8M + /4M + 2M + /1M + RAS
1M: = /8M * 4M * /2M * 1M * /RAS +
/1M * 8M * /4M * /RAS +
/1M * /8M * 4M * 2M * /RAS +
/1M * RAS +
/1M * /8M * /4M * /RAS +
/1M * 8M * 4M * /RAS
4M: = 1M * RAS +
8M * 4M * 2M * /1M * RAS +
/8M * /4M * /1M * RAS +
8M * /4M * 2M * /1M * RAS +
/8M * 4M * /2M * /RAS +
there may be a line missing here.....
2M: = /C16M * /8M * /4M * /RAS
+ /2M + /8M + /4M
+ /2M + /1M + * /TC
+ C16M * /2M
+ /C16M * /8M * /4M * /1M * RAS * /ROMEN * /RAMEN * /AS
+ /2M * 4M
+ /2M * 8M * /4M *1M * MU
DTACK := /C16M * /8M * /4M * /RAS * /AS * /ROMEN * RAMEN
+ /C16M * /8M * /4M * /1M * /RAS * /AS * /RAMEN * ROMEN
+ /C16M * /8M * /4M * 1M * /RAS * /AS * /RAMEN * ROMEN * /MU
+ /C16M * /8M * 4M * /1M * RAS * /AS * /RAMEN * /ROMEN
+ /DTACK * /UDS
+ /DATACK * /LDS
+ /DATACK * /RAS
This is probably not right for the Mac Plus...
CAS0: = 4M * /2M * /RAS * /DTACK * /RAMEN * ROMEN * /LDS * MU
+ 4M * /2M * 1M * /RAS * MU
+ /CAS0
+ /RAS
+ 8M + 4M + /2M * /1M * RAS * /DTACK
+ /CAS0 * /2M + /1M
CAS1: = 4M * /2M * /RAS * /DTACK * /RAMEN * ROMEN * /UDS * MU
+ 4M * /2M * 1M * /RAS * MU
+ /CAS1 + /RAS
I actually have a board with BrainStorm installed.
However, it doesn't have a BrainStorm screen at startup, and after booting, the BrainStorm software gives an error when updating the firmware. Possibly the GAL seems to be broken. If you know what GAL chips they are, I may be able to flash to the farmware with an update from an empty GAL, but that's just my imagination.
And there is a blue plate under the genuine ROM (HI / LO), but if I remove this, it will be a SadMac. The blue plate has terminals at all four corners, each with no continuity.
I can sacrifice this board if reverse engineering is successful. Of course, I would be most happy if I could get a GAL chip. However, the board as it is is just garbage
However, it doesn't have a BrainStorm screen at startup, and after booting, the BrainStorm software gives an error when updating the firmware. Possibly the GAL seems to be broken. If you know what GAL chips they are, I may be able to flash to the farmware with an update from an empty GAL, but that's just my imagination.
And there is a blue plate under the genuine ROM (HI / LO), but if I remove this, it will be a SadMac. The blue plate has terminals at all four corners, each with no continuity.
I can sacrifice this board if reverse engineering is successful. Of course, I would be most happy if I could get a GAL chip. However, the board as it is is just garbage
Attachments
I would personally be very interested in a newly-made Brainstorm for my Plus!
I just removed the broken Brianstorm from my board. If anyone reverse engineers, I would like to offer this for free. However, there is a premise that you will definitely challenge it. I would like to give it to someone who can get started immediately without procrastination.
They are the shields that underlie the ROMs. Curiously, I couldn't boot the MacPlus without them. There is no continuity between the 4 pins.
I have a mac plus with the brainstorm. I was able to update the firmware and it did help with the sound.
Its also kinda interesting because it accelerates via upping the bus. So you need to make sure you have fast ram for it also.
My computer is unstable. I'm not sure if its the brainstorm or if its something else.....
Its also kinda interesting because it accelerates via upping the bus. So you need to make sure you have fast ram for it also.
My computer is unstable. I'm not sure if its the brainstorm or if its something else.....
I suspect he is meant to be Hermes! No golf shirt I'm afraid, haha.
Image credits:
Brainstorm Accelerator User's Guide - SavageTaylor.com
Hermes & Dionysus - Museum of Antiquities, via usask.ca (Univ. of Saskatchewan)
Image credits:
Brainstorm Accelerator User's Guide - SavageTaylor.com
Hermes & Dionysus - Museum of Antiquities, via usask.ca (Univ. of Saskatchewan)
Last edited: