aliu@sal43.usc.edu (Alejandro Liu) (01/21/89)
I heard a while back that it is possible to use the 1764 in the C-128,
since the 1764 was identical to the 1750 REU except for ONE resistor.
Is this true? Can anybody confirm or deny this?
aliu@nunki.usc.edu (Alejandro Liu)
(Simple .signature, $CHEAP$) jgreco@csd4.milw.wisc.edu (Joe Greco) (01/23/89)
In article <2413@nunki.usc.edu> aliu@nunki.usc.edu (Alejandro Liu) writes: >I heard a while back that it is possible to use the 1764 in the C-128, >since the 1764 was identical to the 1750 REU except for ONE resistor. >Is this true? Can anybody confirm or deny this? The 1764 is only a 256K expander. The 1764 comes bundled with a heavy power supply, which is really the major difference. The 1750 is a 512K expander. The "resistor" you mention, if I recall correctly, only involves certain versions of the 128 expanders and early versions of the c64. Perhaps Fred B or some Commodore guru could clear this up, I haven't had any problems running a 1750 on ANY of my machines (even a vintage 1982 model). I've heard of people using the 1764 on the 128, but with somewhat limited success since a fair amount of software is expecting a 1750 (very little seems to expect a 1700). I don't have a 128, so this is just stuff I've heard through the grapevine. I've also heard conflicting stories about the configuration of the 1764's RAM. I know that the 1700 is two banks of 64K, and the 1750 is two banks of 256K. I heard originally that the 1764 was two banks of 128K (!!) (rather odd) but have heard since that it is just one bank of 256K. I know that there could be two versions of the expander out there, has anyone seen either of these two configurations? . JG -- jgreco@csd4.milw.wisc.edu Joe Greco at FidoNet 1:154/200 USnail: 9905 W Montana Ave PunterNet Node 30 or 31 West Allis, WI 53227-3329 "These aren't anybody's opinions." Voice: 414/321-6184 Data: 414/321-9287 (Happy Hacker's BBS)
fred@cbmvax.UUCP (Fred Bowen) (01/24/89)
In article <513@csd4.milw.wisc.edu> jgreco@csd4.milw.wisc.edu (Joe Greco) writes: >In article <2413@nunki.usc.edu> aliu@nunki.usc.edu (Alejandro Liu) writes: >>I heard a while back that it is possible to use the 1764 in the C-128, >>since the 1764 was identical to the 1750 REU except for ONE resistor. >>Is this true? Can anybody confirm or deny this? > >I've also heard conflicting stories about the configuration of the >1764's RAM. Officially, CBM does not recommend using the 1700/1750 expanders on a C64 nor a 1764 expander on a C128. Many people have done this and report no problems. Using any REU on a C64 requires a beefier power supply, which is included with the 1764. The only difference among the REU's, aside from the amount of RAM, is a resistor labeled R4. Its location depends upon the vintage of the board. Its purpose is to slightly shift the timing of the dot clock in relation to other signals on C128's. This is due to slightly different timing between the C64 and C128 systems (TTL delays between the expansion port and VIC & processor chips). 1700's were populated with 2 banks of 64K DRAMs, 1764's with 1 bank of 256K DRAMs, and 1750's with 2 banks of 256K DRAMs. I was not aware of any other configurations. A rather popular hack is increase the amount of DRAM up to 512K bytes by replacing all the DRAMs in a 1700 with 256K DRAMs (and cutting jumper J1), or simply adding the second bank of 256K DRAMs to a 1764. Some people who have both C64 and C128 systems install a switch and 390 ohm resistor at location R4, so that they can switch in the resistor for a C128 and switch it out for a C64. Usual disclaimer- these hacks void your warranty and are done entirely at your own risk. -- -- Fred Bowen uucp: {uunet|rutgers|pyramid}!cbmvax!fred arpa: cbmvax!fred@uunet.uu.net tele: 215 431-9100 Commodore Electronics, Ltd., 1200 Wilson Drive, West Chester, PA, 19380
izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh) (01/24/89)
> From: aliu@sal43.usc.edu (Alejandro Liu) > Message-ID: <2413@nunki.usc.edu> > I heard a while back that it is possible to use the 1764 in the C-128, > since the 1764 was identical to the 1750 REU except for ONE resistor. > Is this true? Can anybody confirm or deny this? Well, there is one more detail: the 1764 has half the RAM of the 1750. Aside of that, they're functionally identical. -- Geoffrey Welsh - via FidoNet node 1:221/162 UUCP: ...!watmath!isishq!171!izot Internet: izot@f171.n221.z1.FIDONET.ORG
izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh) (01/24/89)
> From: jgreco@csd4.milw.wisc.edu (Joe Greco) > Message-ID: <513@csd4.milw.wisc.edu> > > I've heard of people using the 1764 on the 128, but with somewhat > limited success since a fair amount of software is expecting a 1750 > (very little seems to expect a 1700). The problem lies, not with what the software expects, but with what the REU controller reads. There is only one bit to indicate the size of RAM, and most 128 programs test it rather than do a RAM limit test. The 1700 (128K) had the bit cleared, the 1750 (512K) had it set. The 1764 (256K) has it set. I know the folks at CBM are 'listening', so I won't give a detailed opinion on the intelligence of that design decision. > I've also heard conflicting stories about the configuration of the > 1764's RAM. I know that the 1700 is two banks of 64K, and the 1750 is > two banks of 256K. I heard originally that the 1764 was two banks of > 128K (!!) (rather odd) but have heard since that it is just one bank > of 256K. I know that there could be two versions of the expander out > there, has anyone seen either of these two configurations? In terms of hardware, the 1764 uses one bank of 256K DRAMs (some have soldered another 8 RAM chips to bring the cartridge to 512K) but, from a software point of view, ALL the RAM expanders have 64K banks (allowing 16-bit addressing within the bank). =========================================================================== Internet: Geoffrey.Welsh@f171.n221.z1.fidonet.org | 66 Mooregate Crescent Usenet: watmath!isishq!izot | Suite 602 FidoNet: Geoffrey Welsh on 1:221/171 | Kitchener, Ontario PunterNet: 7/Geoffrey Welsh | N2M 5E6 CANADA BBS: (519) 742-8939 24h 7d 300/1200/2400bps | (519) 741-9553 =========================================================================== | "I don't need a disclaimer. No one pays any attention to what I say." | =========================================================================== -- Geoffrey Welsh - via FidoNet node 1:221/162 UUCP: ...!watmath!isishq!171!izot Internet: izot@f171.n221.z1.FIDONET.ORG
MaryFW@cup.portal.com (Mary Ann Fall) (01/24/89)
I've successfully used the 1764 with my C128 for over four months now. In fact, GEOS 128 directly recognizes the 1764 as a RAM 1541. However, the only other program I've found that works with the 1764 in 128 mode is the public domain program REUtility. In 64 mode, however, the 1764 does just fine. But since I have such limited use for it in 128, I have the REU plugged into an expansion cartridge where I can switch it on or off instead of unplugging it. As I understand it, the only difference between the 1764 and the 1750 is the resistor and eight chips. In fact, I know of at least one person (and have heard of others) who have installed the eight chips and effectively turned their 1764 into a 1750--an option I'm considering if the chips can be found in these chip-famished days.